- A large and involved preparatory series to pave the way to add exception
handling for relocate_kernel - which will be a debugging facility that
has aided in the field to debug an exceptionally hard to debug early boot bug.
Plus assorted cleanups and fixes that were discovered along the way,
by David Woodhouse:
- Clean up and document register use in relocate_kernel_64.S
- Use named labels in swap_pages in relocate_kernel_64.S
- Only swap pages for ::preserve_context mode
- Allocate PGD for x86_64 transition page tables separately
- Copy control page into place in machine_kexec_prepare()
- Invoke copy of relocate_kernel() instead of the original
- Move relocate_kernel to kernel .data section
- Add data section to relocate_kernel
- Drop page_list argument from relocate_kernel()
- Eliminate writes through kernel mapping of relocate_kernel page
- Clean up register usage in relocate_kernel()
- Mark relocate_kernel page as ROX instead of RWX
- Disable global pages before writing to control page
- Ensure preserve_context flag is set on return to kernel
- Use correct swap page in swap_pages function
- Fix stack and handling of re-entry point for ::preserve_context
- Mark machine_kexec() with __nocfi
- Cope with relocate_kernel() not being at the start of the page
- Use typedef for relocate_kernel_fn function prototype
- Fix location of relocate_kernel with -ffunction-sections (fix by Nathan Chancellor)
- A series to remove the last remaining absolute symbol references from
.head.text, and enforce this at build time, by Ard Biesheuvel:
- Avoid WARN()s and panic()s in early boot code
- Don't hang but terminate on failure to remap SVSM CA
- Determine VA/PA offset before entering C code
- Avoid intentional absolute symbol references in .head.text
- Disable UBSAN in early boot code
- Move ENTRY_TEXT to the start of the image
- Move .head.text into its own output section
- Reject absolute references in .head.text
- Which build-time enforcement uncovered a handful of bugs of essentially
non-working code, and a wrokaround for a toolchain bug, fixed by
Ard Biesheuvel as well:
- Fix spurious undefined reference when CONFIG_X86_5LEVEL=n, on GCC-12
- Disable UBSAN on SEV code that may execute very early
- Disable ftrace branch profiling in SEV startup code
- And miscellaneous cleanups:
- kexec_core: Add and update comments regarding the KEXEC_JUMP flow (Rafael J. Wysocki)
- x86/sysfs: Constify 'struct bin_attribute' (Thomas Weißschuh)
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-boot-2025-01-21' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 boot updates from Ingo Molnar:
- A large and involved preparatory series to pave the way to add
exception handling for relocate_kernel - which will be a debugging
facility that has aided in the field to debug an exceptionally hard
to debug early boot bug. Plus assorted cleanups and fixes that were
discovered along the way, by David Woodhouse:
- Clean up and document register use in relocate_kernel_64.S
- Use named labels in swap_pages in relocate_kernel_64.S
- Only swap pages for ::preserve_context mode
- Allocate PGD for x86_64 transition page tables separately
- Copy control page into place in machine_kexec_prepare()
- Invoke copy of relocate_kernel() instead of the original
- Move relocate_kernel to kernel .data section
- Add data section to relocate_kernel
- Drop page_list argument from relocate_kernel()
- Eliminate writes through kernel mapping of relocate_kernel page
- Clean up register usage in relocate_kernel()
- Mark relocate_kernel page as ROX instead of RWX
- Disable global pages before writing to control page
- Ensure preserve_context flag is set on return to kernel
- Use correct swap page in swap_pages function
- Fix stack and handling of re-entry point for ::preserve_context
- Mark machine_kexec() with __nocfi
- Cope with relocate_kernel() not being at the start of the page
- Use typedef for relocate_kernel_fn function prototype
- Fix location of relocate_kernel with -ffunction-sections (fix by Nathan Chancellor)
- A series to remove the last remaining absolute symbol references from
.head.text, and enforce this at build time, by Ard Biesheuvel:
- Avoid WARN()s and panic()s in early boot code
- Don't hang but terminate on failure to remap SVSM CA
- Determine VA/PA offset before entering C code
- Avoid intentional absolute symbol references in .head.text
- Disable UBSAN in early boot code
- Move ENTRY_TEXT to the start of the image
- Move .head.text into its own output section
- Reject absolute references in .head.text
- The above build-time enforcement uncovered a handful of bugs of
essentially non-working code, and a wrokaround for a toolchain bug,
fixed by Ard Biesheuvel as well:
- Fix spurious undefined reference when CONFIG_X86_5LEVEL=n, on GCC-12
- Disable UBSAN on SEV code that may execute very early
- Disable ftrace branch profiling in SEV startup code
- And miscellaneous cleanups:
- kexec_core: Add and update comments regarding the KEXEC_JUMP flow (Rafael J. Wysocki)
- x86/sysfs: Constify 'struct bin_attribute' (Thomas Weißschuh)"
* tag 'x86-boot-2025-01-21' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (33 commits)
x86/sev: Disable ftrace branch profiling in SEV startup code
x86/kexec: Use typedef for relocate_kernel_fn function prototype
x86/kexec: Cope with relocate_kernel() not being at the start of the page
kexec_core: Add and update comments regarding the KEXEC_JUMP flow
x86/kexec: Mark machine_kexec() with __nocfi
x86/kexec: Fix location of relocate_kernel with -ffunction-sections
x86/kexec: Fix stack and handling of re-entry point for ::preserve_context
x86/kexec: Use correct swap page in swap_pages function
x86/kexec: Ensure preserve_context flag is set on return to kernel
x86/kexec: Disable global pages before writing to control page
x86/sev: Don't hang but terminate on failure to remap SVSM CA
x86/sev: Disable UBSAN on SEV code that may execute very early
x86/boot/64: Fix spurious undefined reference when CONFIG_X86_5LEVEL=n, on GCC-12
x86/sysfs: Constify 'struct bin_attribute'
x86/kexec: Mark relocate_kernel page as ROX instead of RWX
x86/kexec: Clean up register usage in relocate_kernel()
x86/kexec: Eliminate writes through kernel mapping of relocate_kernel page
x86/kexec: Drop page_list argument from relocate_kernel()
x86/kexec: Add data section to relocate_kernel
x86/kexec: Move relocate_kernel to kernel .data section
...
Ftrace branch profiling inserts absolute references to its metadata at
call sites, and this implies that this kind of instrumentation cannot be
used while executing from the 1:1 mapping of memory.
Therefore, disable ftrace branch profiling in the SEV startup routines,
by disabling it for the entire SEV core source file.
Closes: https://lore.kernel.org/oe-kbuild-all/202501072244.zZrx9864-lkp@intel.com/
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20250107151826.820147-2-ardb+git@google.com
Use the GUEST_TSC_FREQ MSR to discover the TSC frequency instead of
relying on kvm-clock based frequency calibration. Override both CPU and
TSC frequency calibration callbacks with securetsc_get_tsc_khz(). Since
the difference between CPU base and TSC frequency does not apply in this
case, the same callback is being used.
[ bp: Carve out from
https://lore.kernel.org/r/20250106124633.1418972-11-nikunj@amd.com ]
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20250106124633.1418972-11-nikunj@amd.com
The hypervisor should not be intercepting RDTSC/RDTSCP when Secure TSC is
enabled. A #VC exception will be generated if the RDTSC/RDTSCP instructions
are being intercepted. If this should occur and Secure TSC is enabled,
guest execution should be terminated as the guest cannot rely on the TSC
value provided by the hypervisor.
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Tested-by: Peter Gonda <pgonda@google.com>
Link: https://lore.kernel.org/r/20250106124633.1418972-9-nikunj@amd.com
The hypervisor should not be intercepting GUEST_TSC_FREQ MSR(0xcOO10134)
when Secure TSC is enabled. A #VC exception will be generated otherwise. If
this should occur and Secure TSC is enabled, terminate guest execution.
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20250106124633.1418972-8-nikunj@amd.com
Secure TSC enabled guests should not write to the MSR_IA32_TSC (0x10) register
as the subsequent TSC value reads are undefined. On AMD, MSR_IA32_TSC is
intercepted by the hypervisor by default. MSR_IA32_TSC read/write accesses
should not exit to the hypervisor for such guests.
Accesses to MSR_IA32_TSC need special handling in the #VC handler for the
guests with Secure TSC enabled. Writes to MSR_IA32_TSC should be ignored and
flagged once with a warning, and reads of MSR_IA32_TSC should return the
result of the RDTSC instruction.
[ bp: Massage commit message. ]
Suggested-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20250106124633.1418972-7-nikunj@amd.com
Add support for Secure TSC in SNP-enabled guests. Secure TSC allows guests
to securely use RDTSC/RDTSCP instructions, ensuring that the parameters used
cannot be altered by the hypervisor once the guest is launched.
Secure TSC-enabled guests need to query TSC information from the AMD Security
Processor. This communication channel is encrypted between the AMD Security
Processor and the guest, with the hypervisor acting merely as a conduit to
deliver the guest messages to the AMD Security Processor. Each message is
protected with AEAD (AES-256 GCM).
[ bp: Zap a stray newline over amd_cc_platform_has() while at it,
simplify CC_ATTR_GUEST_SNP_SECURE_TSC check ]
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20250106124633.1418972-6-nikunj@amd.com
Commit
09d35045cd ("x86/sev: Avoid WARN()s and panic()s in early boot code")
replaced a panic() that could potentially hit before the kernel is even
mapped with a deadloop, to ensure that execution does not proceed when the
condition in question hits.
As Tom suggests, it is better to terminate and return to the hypervisor
in this case, using a newly invented failure code to describe the
failure condition.
Suggested-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/all/9ce88603-20ca-e644-2d8a-aeeaf79cde69@amd.com
At present, the SEV guest driver exclusively handles SNP guest messaging. All
routines for sending guest messages are embedded within it.
To support Secure TSC, SEV-SNP guests must communicate with the AMD Security
Processor during early boot. However, these guest messaging functions are not
accessible during early boot since they are currently part of the guest
driver.
Hence, relocate the core SNP guest messaging functions to SEV common code and
provide an API for sending SNP guest messages.
No functional change, but just an export symbol added for
snp_send_guest_request() and dropped the export symbol on
snp_issue_guest_request() and made it static.
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20250106124633.1418972-5-nikunj@amd.com
Currently, the sev-guest driver is the only user of SNP guest messaging. All
routines for initializing SNP guest messaging are implemented within the
sev-guest driver and are not available during early boot.
In preparation for adding Secure TSC guest support, carve out APIs to allocate
and initialize the guest messaging descriptor context and make it part of
coco/sev/core.c. As there is no user of sev_guest_platform_data anymore,
remove the structure.
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20250106124633.1418972-4-nikunj@amd.com
Clang 14 and older may emit UBSAN instrumentation into code that is
inlined into functions marked with __no_sanitize_undefined¹. This may
result in faults when the code is executed very early, which may be the
case for functions annotated as __head. Now that this requirement is
strictly enforced, the build will fail in this case with the following
message
Absolute reference to symbol '.data' not permitted in .head.text
Work around this by disabling UBSAN instrumentation on all SEV core
code.
¹ https://lore.kernel.org/r/20250101024348.GA1828419@ax162
[ bp: Add a footnote with Nathan's detailed explanation and a Fixes
tag ]
Fixes: 3b6f99a94b ("x86/boot: Disable UBSAN in early boot code")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20250101115119.114584-2-ardb@kernel.org
Dump TD configuration on boot. Attributes and TD_CTLS define TD
behavior. This information is useful for tracking down bugs.
The output ends up looking like this in practice:
[ 0.000000] tdx: Guest detected
[ 0.000000] tdx: Attributes: SEPT_VE_DISABLE
[ 0.000000] tdx: TD_CTLS: PENDING_VE_DISABLE ENUM_TOPOLOGY VIRT_CPUID2 REDUCE_VE
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Link: https://lore.kernel.org/all/20241202072458.447455-1-kirill.shutemov%40linux.intel.com
The early boot code runs from a 1:1 mapping of memory, and may execute
before the kernel virtual mapping is even up. This means absolute symbol
references cannot be permitted in this code.
UBSAN injects references to global data structures into the code, and
without -fPIC, those references are emitted as absolute references to
kernel virtual addresses. Accessing those will fault before the kernel
virtual mapping is up, so UBSAN needs to be disabled in early boot code.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lore.kernel.org/r/20241205112804.3416920-13-ardb+git@google.com
Using WARN() or panic() while executing from the early 1:1 mapping is
unlikely to do anything useful: the string literals are passed using
their kernel virtual addresses which are not even mapped yet. But even
if they were, calling into the printk() machinery from the early 1:1
mapped code is not going to get very far.
So drop the WARN()s entirely, and replace panic() with a deadloop.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lore.kernel.org/r/20241205112804.3416920-10-ardb+git@google.com
Originally, #VE was defined as the TDX behavior in order to support
paravirtualization of x86 features that can’t be virtualized by the TDX
module. The intention is that if guest software wishes to use such a
feature, it implements some logic to support this. This logic resides in
the #VE exception handler it may work in cooperation with the host VMM.
Theoretically, the guest TD’s #VE handler was supposed to act as a "TDX
enlightenment agent" inside the TD. However, in practice, the #VE
handler is simplistic:
- #VE on CPUID is handled by returning all-0 to the code which
executed CPUID. In many cases, an all-0 value is not the correct
value, and may cause improper operation.
- #VE on RDMSR is handled by requesting the MSR value from the host
VMM. This is prone to security issues since the host VMM is
untrusted. It may also be functionally incorrect in case the
expected operation is to paravirtualize some CPU functionality.
Newer TDX modules provide a "REDUCE_VE" feature. When enabled, it
drastically cuts cases when guests receive #VE on MSR and CPUID
accesses. Basically, instead of punting the problem to the VMM, the
TDX module fills in good data. What the TDX module provides is
obviously highly specific to the MSR or CPUID. This is all spelled
out in excruciating detail in the TDX specs.
Enable REDUCE_VE. Make TDX guest behaviour less odd, and closer to
how a normal CPU behaves.
Note that enabling of the feature doesn't eliminate need in #VE handler
for CPUID and MSR accesses. Some MSRs still generate #VE (notably
APIC-related) and kernel needs CPUID #VE handler to ask VMM for leafs in
hypervisor range.
[ dhansen: changelog tweaks, rename/rework VE reduction function ]
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Link: https://lore.kernel.org/all/20241202072431.447380-1-kirill.shutemov%40linux.intel.com
- Use the newly-available metadata to:
- Disable potentially nasty #VE exceptions
- Get more complete CPU topology information from the VMM
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Merge tag 'x86_tdx_for_6.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull tdx updates from Dave Hansen:
"These essentially refine some interactions between TDX guests and
VMMs.
The first leverages a new TDX module feature to runtime disable the
ability for a VM to inject #VE exceptions. Before this feature, there
was only a static on/off switch and the guest had to panic if it was
configured in a bad state.
The second lets the guest opt in to be able to access the topology
CPUID leaves. Before this, accesses to those leaves would #VE.
For both of these, it would have been nicest to just change the
default behavior, but some pesky "other" OSes evidently need to retain
the legacy behavior.
Summary:
- Add new infrastructure for reading TDX metadata
- Use the newly-available metadata to:
- Disable potentially nasty #VE exceptions
- Get more complete CPU topology information from the VMM"
* tag 'x86_tdx_for_6.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/tdx: Enable CPU topology enumeration
x86/tdx: Dynamically disable SEPT violations from causing #VEs
x86/tdx: Rename tdx_parse_tdinfo() to tdx_setup()
x86/tdx: Introduce wrappers to read and write TD metadata
TDX 1.0 defines baseline behaviour of TDX guest platform. TDX 1.0
generates a #VE when accessing topology-related CPUID leafs (0xB and
0x1F) and the X2APIC_APICID MSR. The kernel returns all zeros on CPUID
topology. In practice, this means that the kernel can only boot with a
plain topology. Any complications will cause problems.
The ENUM_TOPOLOGY feature allows the VMM to provide topology
information to the guest. Enabling the feature eliminates
topology-related #VEs: the TDX module virtualizes accesses to
the CPUID leafs and the MSR.
Enable ENUM_TOPOLOGY if it is available.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/all/20241104103803.195705-5-kirill.shutemov%40linux.intel.com
Memory access #VEs are hard for Linux to handle in contexts like the
entry code or NMIs. But other OSes need them for functionality.
There's a static (pre-guest-boot) way for a VMM to choose one or the
other. But VMMs don't always know which OS they are booting, so they
choose to deliver those #VEs so the "other" OSes will work. That,
unfortunately has left us in the lurch and exposed to these
hard-to-handle #VEs.
The TDX module has introduced a new feature. Even if the static
configuration is set to "send nasty #VEs", the kernel can dynamically
request that they be disabled. Once they are disabled, access to private
memory that is not in the Mapped state in the Secure-EPT (SEPT) will
result in an exit to the VMM rather than injecting a #VE.
Check if the feature is available and disable SEPT #VE if possible.
If the TD is allowed to disable/enable SEPT #VEs, the ATTR_SEPT_VE_DISABLE
attribute is no longer reliable. It reflects the initial state of the
control for the TD, but it will not be updated if someone (e.g. bootloader)
changes it before the kernel starts. Kernel must check TDCS_TD_CTLS bit to
determine if SEPT #VEs are enabled or disabled.
[ dhansen: remove 'return' at end of function ]
Fixes: 373e715e31 ("x86/tdx: Panic on bad configs that #VE on "private" memory access")
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/all/20241104103803.195705-4-kirill.shutemov%40linux.intel.com
Rename tdx_parse_tdinfo() to tdx_setup() and move setting NOTIFY_ENABLES
there.
The function will be extended to adjust TD configuration.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/all/20241104103803.195705-3-kirill.shutemov%40linux.intel.com
The TDG_VM_WR TDCALL is used to ask the TDX module to change some
TD-specific VM configuration. There is currently only one user in the
kernel of this TDCALL leaf. More will be added shortly.
Refactor to make way for more users of TDG_VM_WR who will need to modify
other TD configuration values.
Add a wrapper for the TDG_VM_RD TDCALL that requests TD-specific
metadata from the TDX module. There are currently no users for
TDG_VM_RD. Mark it as __maybe_unused until the first user appears.
This is preparation for enumeration and enabling optional TD features.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Link: https://lore.kernel.org/all/20241104103803.195705-2-kirill.shutemov%40linux.intel.com
Carve out the MSR_SVSM_CAA into a helper with the suggestion that
upcoming future users should do the same. Rename that silly exit_info_1
into what it actually means in this function - whether the MSR access is
a read or a write.
No functional changes.
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@amd.com>
Link: https://lore.kernel.org/r/20241106172647.GAZyum1zngPDwyD2IJ@fat_crate.local
SNP guests allocate shared buffers to perform I/O. It is done by
allocating pages normally from the buddy allocator and converting them
to shared with set_memory_decrypted().
The second, kexec-ed, kernel has no idea what memory is converted this
way. It only sees E820_TYPE_RAM.
Accessing shared memory via private mapping will cause unrecoverable RMP
page-faults.
On kexec, walk direct mapping and convert all shared memory back to
private. It makes all RAM private again and second kernel may use it
normally. Additionally, for SNP guests, convert all bss decrypted
section pages back to private.
The conversion occurs in two steps: stopping new conversions and
unsharing all memory. In the case of normal kexec, the stopping of
conversions takes place while scheduling is still functioning. This
allows for waiting until any ongoing conversions are finished. The
second step is carried out when all CPUs except one are inactive and
interrupts are disabled. This prevents any conflicts with code that may
access shared memory.
Co-developed-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/05a8c15fb665dbb062b04a8cb3d592a63f235937.1722520012.git.ashish.kalra@amd.com
Add a snp_guest_req structure to eliminate the need to pass a long list of
parameters. This structure will be used to call the SNP Guest message
request API, simplifying the function arguments.
Update the snp_issue_guest_request() prototype to include the new guest
request structure.
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20241009092850.197575-5-nikunj@amd.com
Instead of calling get_secrets_page(), which parses the CC blob every time
to get the secrets page physical address (secrets_pa), save the secrets
page physical address during snp_init() from the CC blob. Since
get_secrets_page() is no longer used, remove the function.
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20241009092850.197575-4-nikunj@amd.com
Move SEV-specific kernel command line option parsing support from
arch/x86/coco/sev/core.c to arch/x86/virt/svm/cmdline.c so that both
host and guest related SEV command line options can be supported.
No functional changes intended.
Signed-off-by: Pavan Kumar Paluri <papaluri@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20241014130948.1476946-2-papaluri@amd.com
TDX only supports kernel-initiated MMIO operations. The handle_mmio()
function checks if the #VE exception occurred in the kernel and rejects
the operation if it did not.
However, userspace can deceive the kernel into performing MMIO on its
behalf. For example, if userspace can point a syscall to an MMIO address,
syscall does get_user() or put_user() on it, triggering MMIO #VE. The
kernel will treat the #VE as in-kernel MMIO.
Ensure that the target MMIO address is within the kernel before decoding
instruction.
Fixes: 31d58c4e55 ("x86/tdx: Handle in-kernel MMIO")
Signed-off-by: Alexey Gladkov (Intel) <legion@kernel.org>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc:stable@vger.kernel.org
Link: https://lore.kernel.org/all/565a804b80387970460a4ebc67c88d1380f61ad1.1726237595.git.legion%40kernel.org
The mmio_read() function makes a TDVMCALL to retrieve MMIO data for an
address from the VMM.
Sean noticed that mmio_read() unintentionally exposes the value of an
initialized variable (val) on the stack to the VMM.
This variable is only needed as an output value. It did not need to be
passed to the VMM in the first place.
Do not send the original value of *val to the VMM.
[ dhansen: clarify what 'val' is used for. ]
Fixes: 31d58c4e55 ("x86/tdx: Handle in-kernel MMIO")
Reported-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc:stable@vger.kernel.org
Link: https://lore.kernel.org/all/20240826125304.1566719-1-kirill.shutemov%40linux.intel.com
sev_config currently has debug, ghcbs_initialized, and use_cas fields.
However, __reserved count has not been updated. Fix this.
Fixes: 34ff659017 ("x86/sev: Use kernel provided SVSM Calling Areas")
Signed-off-by: Pavan Kumar Paluri <papaluri@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240729180808.366587-1-papaluri@amd.com
VM Service Module (SVSM).
When running over a SVSM, different services can run at different
protection levels, apart from the guest OS but still within the
secure SNP environment. They can provide services to the guest, like
a vTPM, for example.
This series adds the required facilities to interface with such a SVSM
module.
- The usual fixlets, refactoring and cleanups
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Merge tag 'x86_sev_for_v6.11_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 SEV updates from Borislav Petkov:
- Add support for running the kernel in a SEV-SNP guest, over a Secure
VM Service Module (SVSM).
When running over a SVSM, different services can run at different
protection levels, apart from the guest OS but still within the
secure SNP environment. They can provide services to the guest, like
a vTPM, for example.
This series adds the required facilities to interface with such a
SVSM module.
- The usual fixlets, refactoring and cleanups
[ And as always: "SEV" is AMD's "Secure Encrypted Virtualization".
I can't be the only one who gets all the newer x86 TLA's confused,
can I?
- Linus ]
* tag 'x86_sev_for_v6.11_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
Documentation/ABI/configfs-tsm: Fix an unexpected indentation silly
x86/sev: Do RMP memory coverage check after max_pfn has been set
x86/sev: Move SEV compilation units
virt: sev-guest: Mark driver struct with __refdata to prevent section mismatch
x86/sev: Allow non-VMPL0 execution when an SVSM is present
x86/sev: Extend the config-fs attestation support for an SVSM
x86/sev: Take advantage of configfs visibility support in TSM
fs/configfs: Add a callback to determine attribute visibility
sev-guest: configfs-tsm: Allow the privlevel_floor attribute to be updated
virt: sev-guest: Choose the VMPCK key based on executing VMPL
x86/sev: Provide guest VMPL level to userspace
x86/sev: Provide SVSM discovery support
x86/sev: Use the SVSM to create a vCPU when not in VMPL0
x86/sev: Perform PVALIDATE using the SVSM when not at VMPL0
x86/sev: Use kernel provided SVSM Calling Areas
x86/sev: Check for the presence of an SVSM in the SNP secrets page
x86/irqflags: Provide native versions of the local_irq_save()/restore()
TDX guests allocate shared buffers to perform I/O. It is done by allocating
pages normally from the buddy allocator and converting them to shared with
set_memory_decrypted().
The second, kexec-ed kernel has no idea what memory is converted this way. It
only sees E820_TYPE_RAM.
Accessing shared memory via private mapping is fatal. It leads to unrecoverable
TD exit.
On kexec, walk direct mapping and convert all shared memory back to private. It
makes all RAM private again and second kernel may use it normally.
The conversion occurs in two steps: stopping new conversions and unsharing all
memory. In the case of normal kexec, the stopping of conversions takes place
while scheduling is still functioning. This allows for waiting until any ongoing
conversions are finished. The second step is carried out when all CPUs except one
are inactive and interrupts are disabled. This prevents any conflicts with code
that may access shared memory.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Tested-by: Tao Liu <ltao@redhat.com>
Link: https://lore.kernel.org/r/20240614095904.1345461-12-kirill.shutemov@linux.intel.com
The kernel will convert all shared memory back to private during kexec.
The direct mapping page tables will provide information on which memory
is shared.
It is extremely important to convert all shared memory. If a page is
missed, it will cause the second kernel to crash when it accesses it.
Keep track of the number of shared pages. This will allow for
cross-checking against the shared information in the direct mapping and
reporting if the shared bit is lost.
Memory conversion is slow and does not happen often. Global atomic is
not going to be a bottleneck.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Tested-by: Tao Liu <ltao@redhat.com>
Link: https://lore.kernel.org/r/20240614095904.1345461-10-kirill.shutemov@linux.intel.com
TDX is going to have more than one reason to fail enc_status_change_prepare().
Change the callback to return errno instead of assuming -EIO. Change
enc_status_change_finish() too to keep the interface symmetric.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Tao Liu <ltao@redhat.com>
Link: https://lore.kernel.org/r/20240614095904.1345461-8-kirill.shutemov@linux.intel.com
ACPI MADT doesn't allow to offline a CPU after it has been woken up.
Currently, CPU hotplug is prevented based on the confidential computing
attribute which is set for Intel TDX. But TDX is not the only possible user of
the wake up method. Any platform that uses ACPI MADT wakeup method cannot
offline CPU.
Disable CPU offlining on ACPI MADT wakeup enumeration.
This has no visible effects for users: currently, TDX guest is the only platform
that uses the ACPI MADT wakeup method.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Tao Liu <ltao@redhat.com>
Link: https://lore.kernel.org/r/20240614095904.1345461-5-kirill.shutemov@linux.intel.com
Add functionality to set and/or clear different attributes of the
machine as a confidential computing platform. Add the first one too:
whether the machine is running as a host for SEV-SNP guests.
Fixes: 216d106c7f ("x86/sev: Add SEV-SNP host initialization support")
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Tested-by: Srikanth Aithal <sraithal@amd.com>
Link: https://lore.kernel.org/r/20240327154317.29909-5-bp@alien8.de
There are few uses of CoCo that don't rely on working cryptography and
hence a working RNG. Unfortunately, the CoCo threat model means that the
VM host cannot be trusted and may actively work against guests to
extract secrets or manipulate computation. Since a malicious host can
modify or observe nearly all inputs to guests, the only remaining source
of entropy for CoCo guests is RDRAND.
If RDRAND is broken -- due to CPU hardware fault -- the RNG as a whole
is meant to gracefully continue on gathering entropy from other sources,
but since there aren't other sources on CoCo, this is catastrophic.
This is mostly a concern at boot time when initially seeding the RNG, as
after that the consequences of a broken RDRAND are much more
theoretical.
So, try at boot to seed the RNG using 256 bits of RDRAND output. If this
fails, panic(). This will also trigger if the system is booted without
RDRAND, as RDRAND is essential for a safe CoCo boot.
Add this deliberately to be "just a CoCo x86 driver feature" and not
part of the RNG itself. Many device drivers and platforms have some
desire to contribute something to the RNG, and add_device_randomness()
is specifically meant for this purpose.
Any driver can call it with seed data of any quality, or even garbage
quality, and it can only possibly make the quality of the RNG better or
have no effect, but can never make it worse.
Rather than trying to build something into the core of the RNG, consider
the particular CoCo issue just a CoCo issue, and therefore separate it
all out into driver (well, arch/platform) code.
[ bp: Massage commit message. ]
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Elena Reshetova <elena.reshetova@intel.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240326160735.73531-1-Jason@zx2c4.com
The early startup code executes from a 1:1 mapping of memory, which
differs from the mapping that the code was linked and/or relocated to
run at. The latter mapping is not active yet at this point, and so
symbol references that rely on it will fault.
Given that the core kernel is built without -fPIC, symbol references are
typically emitted as absolute, and so any such references occuring in
the early startup code will therefore crash the kernel.
While an attempt was made to work around this for the early SEV/SME
startup code, by forcing RIP-relative addressing for certain global
SEV/SME variables via inline assembly (see snp_cpuid_get_table() for
example), RIP-relative addressing must be pervasively enforced for
SEV/SME global variables when accessed prior to page table fixups.
__startup_64() already handles this issue for select non-SEV/SME global
variables using fixup_pointer(), which adjusts the pointer relative to a
`physaddr` argument. To avoid having to pass around this `physaddr`
argument across all functions needing to apply pointer fixups, introduce
a macro RIP_RELATIVE_REF() which generates a RIP-relative reference to
a given global variable. It is used where necessary to force
RIP-relative accesses to global variables.
For backporting purposes, this patch makes no attempt at cleaning up
other occurrences of this pattern, involving either inline asm or
fixup_pointer(). Those will be addressed later.
[ bp: Call it "rip_rel_ref" everywhere like other code shortens
"rIP-relative reference" and make the asm wrapper __always_inline. ]
Co-developed-by: Kevin Loughlin <kevinloughlin@google.com>
Signed-off-by: Kevin Loughlin <kevinloughlin@google.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@kernel.org>
Link: https://lore.kernel.org/all/20240130220845.1978329-1-kevinloughlin@google.com
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Merge tag 'x86_tdx_for_6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 TDX updates from Dave Hansen:
"This contains the initial support for host-side TDX support so that
KVM can run TDX-protected guests. This does not include the actual
KVM-side support which will come from the KVM folks. The TDX host
interactions with kexec also needs to be ironed out before this is
ready for prime time, so this code is currently Kconfig'd off when
kexec is on.
The majority of the code here is the kernel telling the TDX module
which memory to protect and handing some additional memory over to it
to use to store TDX module metadata. That sounds pretty simple, but
the TDX architecture is rather flexible and it takes quite a bit of
back-and-forth to say, "just protect all memory, please."
There is also some code tacked on near the end of the series to handle
a hardware erratum. The erratum can make software bugs such as a
kernel write to TDX-protected memory cause a machine check and
masquerade as a real hardware failure. The erratum handling watches
out for these and tries to provide nicer user errors"
* tag 'x86_tdx_for_6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (21 commits)
x86/virt/tdx: Make TDX host depend on X86_MCE
x86/virt/tdx: Disable TDX host support when kexec is enabled
Documentation/x86: Add documentation for TDX host support
x86/mce: Differentiate real hardware #MCs from TDX erratum ones
x86/cpu: Detect TDX partial write machine check erratum
x86/virt/tdx: Handle TDX interaction with sleep and hibernation
x86/virt/tdx: Initialize all TDMRs
x86/virt/tdx: Configure global KeyID on all packages
x86/virt/tdx: Configure TDX module with the TDMRs and global KeyID
x86/virt/tdx: Designate reserved areas for all TDMRs
x86/virt/tdx: Allocate and set up PAMTs for TDMRs
x86/virt/tdx: Fill out TDMRs to cover all TDX memory regions
x86/virt/tdx: Add placeholder to construct TDMRs to cover all TDX memory regions
x86/virt/tdx: Get module global metadata for module initialization
x86/virt/tdx: Use all system memory when initializing TDX module as TDX memory
x86/virt/tdx: Add skeleton to enable TDX on demand
x86/virt/tdx: Add SEAMCALL error printing for module initialization
x86/virt/tdx: Handle SEAMCALL no entropy error in common code
x86/virt/tdx: Make INTEL_TDX_HOST depend on X86_X2APIC
x86/virt/tdx: Define TDX supported page sizes as macros
...
- A micro-optimization got misplaced as a cleanup:
- Micro-optimize the asm code in secondary_startup_64_no_verify()
- Change global variables to local
- Add missing kernel-doc function parameter descriptions
- Remove unused parameter from a macro
- Remove obsolete Kconfig entry
- Fix comments
- Fix typos, mostly scripted, manually reviewed
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-cleanups-2024-01-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 cleanups from Ingo Molnar:
- Change global variables to local
- Add missing kernel-doc function parameter descriptions
- Remove unused parameter from a macro
- Remove obsolete Kconfig entry
- Fix comments
- Fix typos, mostly scripted, manually reviewed
and a micro-optimization got misplaced as a cleanup:
- Micro-optimize the asm code in secondary_startup_64_no_verify()
* tag 'x86-cleanups-2024-01-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
arch/x86: Fix typos
x86/head_64: Use TESTB instead of TESTL in secondary_startup_64_no_verify()
x86/docs: Remove reference to syscall trampoline in PTI
x86/Kconfig: Remove obsolete config X86_32_SMP
x86/io: Remove the unused 'bw' parameter from the BUILDIO() macro
x86/mtrr: Document missing function parameters in kernel-doc
x86/setup: Make relocated_ramdisk a local variable of relocate_initrd()
TDX supports 4K, 2M and 1G page sizes. The corresponding values are
defined by the TDX module spec and used as TDX module ABI. Currently,
they are used in try_accept_one() when the TDX guest tries to accept a
page. However currently try_accept_one() uses hard-coded magic values.
Define TDX supported page sizes as macros and get rid of the hard-coded
values in try_accept_one(). TDX host support will need to use them too.
Signed-off-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/all/20231208170740.53979-2-dave.hansen%40intel.com
32-bit emulation was disabled on TDX to prevent a possible attack by
a VMM injecting an interrupt on vector 0x80.
Now that int80_emulation() has a check for external interrupts the
limitation can be lifted.
To distinguish software interrupts from external ones, int80_emulation()
checks the APIC ISR bit relevant to the 0x80 vector. For
software interrupts, this bit will be 0.
On TDX, the VAPIC state (including ISR) is protected and cannot be
manipulated by the VMM. The ISR bit is set by the microcode flow during
the handling of posted interrupts.
[ dhansen: more changelog tweaks ]
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@vger.kernel.org> # v6.0+
The INT 0x80 instruction is used for 32-bit x86 Linux syscalls. The
kernel expects to receive a software interrupt as a result of the INT
0x80 instruction. However, an external interrupt on the same vector
triggers the same handler.
The kernel interprets an external interrupt on vector 0x80 as a 32-bit
system call that came from userspace.
A VMM can inject external interrupts on any arbitrary vector at any
time. This remains true even for TDX and SEV guests where the VMM is
untrusted.
Put together, this allows an untrusted VMM to trigger int80 syscall
handling at any given point. The content of the guest register file at
that moment defines what syscall is triggered and its arguments. It
opens the guest OS to manipulation from the VMM side.
Disable 32-bit emulation by default for TDX and SEV. User can override
it with the ia32_emulation=y command line option.
[ dhansen: reword the changelog ]
Reported-by: Supraja Sridhara <supraja.sridhara@inf.ethz.ch>
Reported-by: Benedict Schlüter <benedict.schlueter@inf.ethz.ch>
Reported-by: Mark Kuhne <mark.kuhne@inf.ethz.ch>
Reported-by: Andrin Bertschi <andrin.bertschi@inf.ethz.ch>
Reported-by: Shweta Shinde <shweta.shinde@inf.ethz.ch>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@vger.kernel.org> # v6.0+: 1da5c9b x86: Introduce ia32_enabled()
Cc: <stable@vger.kernel.org> # v6.0+
- Introduce configfs-tsm as a shared ABI for confidential computing
attestation reports
- Convert sev-guest to additionally support configfs-tsm alongside its
vendor specific ioctl()
- Added signed attestation report retrieval to the tdx-guest driver
forgoing a new vendor specific ioctl()
- Misc. cleanups and a new __free() annotation for kvfree()
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Merge tag 'tsm-for-6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/djbw/linux
Pull unified attestation reporting from Dan Williams:
"In an ideal world there would be a cross-vendor standard attestation
report format for confidential guests along with a common device
definition to act as the transport.
In the real world the situation ended up with multiple platform
vendors inventing their own attestation report formats with the
SEV-SNP implementation being a first mover to define a custom
sev-guest character device and corresponding ioctl(). Later, this
configfs-tsm proposal intercepted an attempt to add a tdx-guest
character device and a corresponding new ioctl(). It also anticipated
ARM and RISC-V showing up with more chardevs and more ioctls().
The proposal takes for granted that Linux tolerates the vendor report
format differentiation until a standard arrives. From talking with
folks involved, it sounds like that standardization work is unlikely
to resolve anytime soon. It also takes the position that kernfs ABIs
are easier to maintain than ioctl(). The result is a shared configfs
mechanism to return per-vendor report-blobs with the option to later
support a standard when that arrives.
Part of the goal here also is to get the community into the
"uncomfortable, but beneficial to the long term maintainability of the
kernel" state of talking to each other about their differentiation and
opportunities to collaborate. Think of this like the device-driver
equivalent of the common memory-management infrastructure for
confidential-computing being built up in KVM.
As for establishing an "upstream path for cross-vendor
confidential-computing device driver infrastructure" this is something
I want to discuss at Plumbers. At present, the multiple vendor
proposals for assigning devices to confidential computing VMs likely
needs a new dedicated repository and maintainer team, but that is a
discussion for v6.8.
For now, Greg and Thomas have acked this approach and this is passing
is AMD, Intel, and Google tests.
Summary:
- Introduce configfs-tsm as a shared ABI for confidential computing
attestation reports
- Convert sev-guest to additionally support configfs-tsm alongside
its vendor specific ioctl()
- Added signed attestation report retrieval to the tdx-guest driver
forgoing a new vendor specific ioctl()
- Misc cleanups and a new __free() annotation for kvfree()"
* tag 'tsm-for-6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/djbw/linux:
virt: tdx-guest: Add Quote generation support using TSM_REPORTS
virt: sevguest: Add TSM_REPORTS support for SNP_GET_EXT_REPORT
mm/slab: Add __free() support for kvfree
virt: sevguest: Prep for kernel internal get_ext_report()
configfs-tsm: Introduce a shared ABI for attestation reports
virt: coco: Add a coco/Makefile and coco/Kconfig
virt: sevguest: Fix passing a stack buffer as a scatterlist target
* Handle retrying/resuming page conversion hypercalls
* Make sure to use the (shockingly) reliable TSC in TDX guests
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Merge tag 'x86_tdx_for_6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 TDX updates from Dave Hansen:
"The majority of this is a rework of the assembly and C wrappers that
are used to talk to the TDX module and VMM. This is a nice cleanup in
general but is also clearing the way for using this code when Linux is
the TDX VMM.
There are also some tidbits to make TDX guests play nicer with Hyper-V
and to take advantage the hardware TSC.
Summary:
- Refactor and clean up TDX hypercall/module call infrastructure
- Handle retrying/resuming page conversion hypercalls
- Make sure to use the (shockingly) reliable TSC in TDX guests"
[ TLA reminder: TDX is "Trust Domain Extensions", Intel's guest VM
confidentiality technology ]
* tag 'x86_tdx_for_6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/tdx: Mark TSC reliable
x86/tdx: Fix __noreturn build warning around __tdx_hypercall_failed()
x86/virt/tdx: Make TDX_MODULE_CALL handle SEAMCALL #UD and #GP
x86/virt/tdx: Wire up basic SEAMCALL functions
x86/tdx: Remove 'struct tdx_hypercall_args'
x86/tdx: Reimplement __tdx_hypercall() using TDX_MODULE_CALL asm
x86/tdx: Make TDX_HYPERCALL asm similar to TDX_MODULE_CALL
x86/tdx: Extend TDX_MODULE_CALL to support more TDCALL/SEAMCALL leafs
x86/tdx: Pass TDCALL/SEAMCALL input/output registers via a structure
x86/tdx: Rename __tdx_module_call() to __tdcall()
x86/tdx: Make macros of TDCALLs consistent with the spec
x86/tdx: Skip saving output regs when SEAMCALL fails with VMFailInvalid
x86/tdx: Zero out the missing RSI in TDX_HYPERCALL macro
x86/tdx: Retry partially-completed page conversion hypercalls
In TDX guest, the attestation process is used to verify the TDX guest
trustworthiness to other entities before provisioning secrets to the
guest. The first step in the attestation process is TDREPORT
generation, which involves getting the guest measurement data in the
format of TDREPORT, which is further used to validate the authenticity
of the TDX guest. TDREPORT by design is integrity-protected and can
only be verified on the local machine.
To support remote verification of the TDREPORT in a SGX-based
attestation, the TDREPORT needs to be sent to the SGX Quoting Enclave
(QE) to convert it to a remotely verifiable Quote. SGX QE by design can
only run outside of the TDX guest (i.e. in a host process or in a
normal VM) and guest can use communication channels like vsock or
TCP/IP to send the TDREPORT to the QE. But for security concerns, the
TDX guest may not support these communication channels. To handle such
cases, TDX defines a GetQuote hypercall which can be used by the guest
to request the host VMM to communicate with the SGX QE. More details
about GetQuote hypercall can be found in TDX Guest-Host Communication
Interface (GHCI) for Intel TDX 1.0, section titled
"TDG.VP.VMCALL<GetQuote>".
Trusted Security Module (TSM) [1] exposes a common ABI for Confidential
Computing Guest platforms to get the measurement data via ConfigFS.
Extend the TSM framework and add support to allow an attestation agent
to get the TDX Quote data (included usage example below).
report=/sys/kernel/config/tsm/report/report0
mkdir $report
dd if=/dev/urandom bs=64 count=1 > $report/inblob
hexdump -C $report/outblob
rmdir $report
GetQuote TDVMCALL requires TD guest pass a 4K aligned shared buffer
with TDREPORT data as input, which is further used by the VMM to copy
the TD Quote result after successful Quote generation. To create the
shared buffer, allocate a large enough memory and mark it shared using
set_memory_decrypted() in tdx_guest_init(). This buffer will be re-used
for GetQuote requests in the TDX TSM handler.
Although this method reserves a fixed chunk of memory for GetQuote
requests, such one time allocation can help avoid memory fragmentation
related allocation failures later in the uptime of the guest.
Since the Quote generation process is not time-critical or frequently
used, the current version uses a polling model for Quote requests and
it also does not support parallel GetQuote requests.
Link: https://lore.kernel.org/lkml/169342399185.3934343.3035845348326944519.stgit@dwillia2-xfh.jf.intel.com/ [1]
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Erdem Aktas <erdemaktas@google.com>
Tested-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Tested-by: Peter Gonda <pgonda@google.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
In x86 virtualization environments, including TDX, RDTSC instruction is
handled without causing a VM exit, resulting in minimal overhead and
jitters. On the other hand, other clock sources (such as HPET, ACPI
timer, APIC, etc.) necessitate VM exits to implement, resulting in more
fluctuating measurements compared to TSC. Thus, those clock sources are
not effective for calibrating TSC.
As a foundation, the host TSC is guaranteed to be invariant on any
system which enumerates TDX support.
TDX guests and the TDX module build on that foundation by enforcing:
- Virtual TSC is monotonously incrementing for any single VCPU;
- Virtual TSC values are consistent among all the TD’s VCPUs at the
level supported by the CPU:
+ VMM is required to set the same TSC_ADJUST;
+ VMM must not modify from initial value of TSC_ADJUST before
SEAMCALL;
- The frequency is determined by TD configuration:
+ Virtual TSC frequency is specified by VMM on TDH.MNG.INIT;
+ Virtual TSC starts counting from 0 at TDH.MNG.INIT;
The result is that a reliable TSC is a TDX architectural guarantee.
Use the TSC as the only reliable clock source in TD guests, bypassing
unstable calibration.
This is similar to what the kernel already does in some VMWare and
HyperV environments.
[ dhansen: changelog tweaks ]
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Erdem Aktas <erdemaktas@google.com>
Reviewed-by: Isaku Yamahata <isaku.yamahata@intel.com>
Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/all/20231006144549.2633-1-kirill.shutemov%40linux.intel.com
Now 'struct tdx_hypercall_args' is basically 'struct tdx_module_args'
minus RCX. Although from __tdx_hypercall()'s perspective RCX isn't
used as shared register thus not part of input/output registers, it's
not worth to have a separate structure just due to one register.
Remove the 'struct tdx_hypercall_args' and use 'struct tdx_module_args'
instead in __tdx_hypercall() related code. This also saves the memory
copy between the two structures within __tdx_hypercall().
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/798dad5ce24e9d745cf0e16825b75ccc433ad065.1692096753.git.kai.huang%40intel.com
Now the TDX_HYPERCALL asm is basically identical to the TDX_MODULE_CALL
with both '\saved' and '\ret' enabled, with two minor things though:
1) The way to restore the structure pointer is different
The TDX_HYPERCALL uses RCX as spare to restore the structure pointer,
but the TDX_MODULE_CALL assumes no spare register can be used. In other
words, TDX_MODULE_CALL already covers what TDX_HYPERCALL does.
2) TDX_MODULE_CALL only clears shared registers for TDH.VP.ENTER
For this just need to make that code available for the non-host case.
Thus, remove the TDX_HYPERCALL and reimplement the __tdx_hypercall()
using the TDX_MODULE_CALL.
Extend the TDX_MODULE_CALL to cover "clear shared registers" for
TDG.VP.VMCALL. Introduce a new __tdcall_saved_ret() to replace the
temporary __tdcall_hypercall().
The __tdcall_saved_ret() can also be used for those new TDCALLs which
require more input/output registers than the basic TDCALLs do.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/e68a2473fb6f5bcd78b078cae7510e9d0753b3df.1692096753.git.kai.huang%40intel.com
