KVM SEV cache maintenance changes for 6.17
- Drop a superfluous WBINVD (on all CPUs!) when destroying a VM.
- Use WBNOINVD instead of WBINVD when possible, for SEV cache maintenance,
e.g. to minimize collateral damage when reclaiming memory from an SEV guest.
- When reclaiming memory from an SEV guest, only do cache flushes on CPUs that
have ever run a vCPU for the guest, i.e. don't flush the caches for CPUs
that can't possibly have cache lines with dirty, encrypted data.
KVM x86 misc changes for 6.17
- Prevert the host's DEBUGCTL.FREEZE_IN_SMM (Intel only) when running the
guest. Failure to honor FREEZE_IN_SMM can bleed host state into the guest.
- Explicitly check vmcs12.GUEST_DEBUGCTL on nested VM-Enter (Intel only) to
prevent L1 from running L2 with features that KVM doesn't support, e.g. BTF.
- Intercept SPEC_CTRL on AMD if the MSR shouldn't exist according to the
vCPU's CPUID model.
- Rework the MSR interception code so that the SVM and VMX APIs are more or
less identical.
- Recalculate all MSR intercepts from the "source" on MSR filter changes, and
drop the dedicated "shadow" bitmaps (and their awful "max" size defines).
- WARN and reject loading kvm-amd.ko instead of panicking the kernel if the
nested SVM MSRPM offsets tracker can't handle an MSR.
- Advertise support for LKGS (Load Kernel GS base), a new instruction that's
loosely related to FRED, but is supported and enumerated independently.
- Fix a user-triggerable WARN that syzkaller found by stuffing INIT_RECEIVED,
a.k.a. WFS, and then putting the vCPU into VMX Root Mode (post-VMXON). Use
the same approach KVM uses for dealing with "impossible" emulation when
running a !URG guest, and simply wait until KVM_RUN to detect that the vCPU
has architecturally impossible state.
- Add KVM_X86_DISABLE_EXITS_APERFMPERF to allow disabling interception of
APERF/MPERF reads, so that a "properly" configured VM can "virtualize"
APERF/MPERF (with many caveats).
- Reject KVM_SET_TSC_KHZ if vCPUs have been created, as changing the "default"
frequency is unsupported for VMs with a "secure" TSC, and there's no known
use case for changing the default frequency for other VM types.
On AMD CPUs without ensuring cache consistency, each memory page
reclamation in an SEV guest triggers a call to do WBNOINVD/WBINVD on all
CPUs, thereby affecting the performance of other programs on the host.
Typically, an AMD server may have 128 cores or more, while the SEV guest
might only utilize 8 of these cores. Meanwhile, host can use qemu-affinity
to bind these 8 vCPUs to specific physical CPUs.
Therefore, keeping a record of the physical core numbers each time a vCPU
runs can help avoid flushing the cache for all CPUs every time.
Take care to allocate the cpumask used to track which CPUs have run a
vCPU when copying or moving an "encryption context", as nothing guarantees
memory in a mirror VM is a strict subset of the ASID owner, and the
destination VM for intrahost migration needs to maintain it's own set of
CPUs. E.g. for intrahost migration, if a CPU was used for the source VM
but not the destination VM, then it can only have cached memory that was
accessible to the source VM. And a CPU that was run in the source is also
used by the destination is no different than a CPU that was run in the
destination only.
Note, KVM is guaranteed to do flush caches prior to sev_vm_destroy(),
thanks to kvm_arch_guest_memory_reclaimed for SEV and SEV-ES, and
kvm_arch_gmem_invalidate() for SEV-SNP. I.e. it's safe to free the
cpumask prior to unregistering encrypted regions and freeing the ASID.
Opportunistically clean up sev_vm_destroy()'s comment regarding what is
(implicitly, what isn't) skipped for mirror VMs.
Cc: Srikanth Aithal <sraithal@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Zheyun Shen <szy0127@sjtu.edu.cn>
Link: https://lore.kernel.org/r/20250522233733.3176144-9-seanjc@google.com
Link: https://lore.kernel.org/all/935a82e3-f7ad-47d7-aaaf-f3d2b62ed768@amd.com
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Extract a common function from MSR interception disabling logic and create
disabling and enabling functions based on it. This removes most of the
duplicated code for MSR interception disabling/enabling.
No functional change intended.
Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20250612081947.94081-2-chao.gao@intel.com
[sean: s/enable/set, inline the wrappers]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Hoist the logic for identifying the target vCPU for a posted interrupt
into common x86. The code is functionally identical between Intel and
AMD.
Tested-by: Sairaj Kodilkar <sarunkod@amd.com>
Link: https://lore.kernel.org/r/20250611224604.313496-30-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Let userspace "disable" IPI virtualization for AVIC via the enable_ipiv
module param, by never setting IsRunning. SVM doesn't provide a way to
disable IPI virtualization in hardware, but by ensuring CPUs never see
IsRunning=1, every IPI in the guest (except for self-IPIs) will generate a
VM-Exit.
To avoid setting the real IsRunning bit, while still allowing KVM to use
each vCPU's entry to update GA log entries, simply maintain a shadow of
the entry, without propagating IsRunning updates to the real table when
IPI virtualization is disabled.
Providing a way to effectively disable IPI virtualization will allow KVM
to safely enable AVIC on hardware that is susceptible to erratum #1235,
which causes hardware to sometimes fail to detect that the IsRunning bit
has been cleared by software.
Note, the table _must_ be fully populated, as broadcast IPIs skip invalid
entries, i.e. won't generate VM-Exit if every entry is invalid, and so
simply pointing the VMCB at a common dummy table won't work.
Alternatively, KVM could allocate a shadow of the entire table, but that'd
be a waste of 4KiB since the per-vCPU entry doesn't actually consume an
additional 8 bytes of memory (vCPU structures are large enough that they
are backed by order-N pages).
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
[sean: keep "entry" variables, reuse enable_ipiv, split from erratum]
Link: https://lore.kernel.org/r/20250611224604.313496-19-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Drop the vCPU's pointer to its AVIC Physical ID entry, and simply index
the table directly. Caching a pointer address is completely unnecessary
for performance, and while the field technically caches the result of the
pointer calculation, it's all too easy to misinterpret the name and think
that the field somehow caches the _data_ in the table.
No functional change intended.
Suggested-by: Maxim Levitsky <mlevitsk@redhat.com>
Tested-by: Sairaj Kodilkar <sarunkod@amd.com>
Reviewed-by: Naveen N Rao (AMD) <naveen@kernel.org>
Link: https://lore.kernel.org/r/20250611224604.313496-17-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Allocate and track AVIC's logical and physical tables as u32 and u64
pointers respectively, as managing the pages as "struct page" pointers
adds an almost absurd amount of boilerplate and complexity. E.g. with
page_address() out of the way, svm->avic_physical_id_cache becomes
completely superfluous, and will be removed in a future cleanup.
No functional change intended.
Tested-by: Sairaj Kodilkar <sarunkod@amd.com>
Acked-by: Naveen N Rao (AMD) <naveen@kernel.org>
Link: https://lore.kernel.org/r/20250611224604.313496-16-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Inhibit AVIC with a new "ID too big" flag if userspace creates a vCPU with
an ID that is too big, but otherwise allow vCPU creation to succeed.
Rejecting KVM_CREATE_VCPU with EINVAL violates KVM's ABI as KVM advertises
that the max vCPU ID is 4095, but disallows creating vCPUs with IDs bigger
than 254 (AVIC) or 511 (x2AVIC).
Alternatively, KVM could advertise an accurate value depending on which
AVIC mode is in use, but that wouldn't really solve the underlying problem,
e.g. would be a breaking change if KVM were to ever try and enable AVIC or
x2AVIC by default.
Cc: Maxim Levitsky <mlevitsk@redhat.com>
Tested-by: Sairaj Kodilkar <sarunkod@amd.com>
Link: https://lore.kernel.org/r/20250611224604.313496-14-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Drop vcpu_svm's avic_backing_page pointer and instead grab the physical
address of KVM's vAPIC page directly from the source. Getting a physical
address from a kernel virtual address is not an expensive operation, and
getting the physical address from a struct page is *more* expensive for
CONFIG_SPARSEMEM=y kernels. Regardless, none of the paths that consume
the address are hot paths, i.e. shaving cycles is not a priority.
Eliminating the "cache" means KVM doesn't have to worry about the cache
being invalid, which will simplify a future fix when dealing with vCPU IDs
that are too big.
WARN if KVM attempts to allocate a vCPU's AVIC backing page without an
in-kernel local APIC. avic_init_vcpu() bails early if the APIC is not
in-kernel, and KVM disallows enabling an in-kernel APIC after vCPUs have
been created, i.e. it should be impossible to reach
avic_init_backing_page() without the vAPIC being allocated.
Tested-by: Sairaj Kodilkar <sarunkod@amd.com>
Reviewed-by: Naveen N Rao (AMD) <naveen@kernel.org>
Link: https://lore.kernel.org/r/20250611224604.313496-13-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Track the IRTEs that are posting to an SVM vCPU via the associated irqfd
structure and GSI routing instead of dynamically allocating a separate
data structure. In addition to eliminating an atomic allocation, this
will allow hoisting much of the IRTE update logic to common x86.
Cc: Sairaj Kodilkar <sarunkod@amd.com>
Link: https://lore.kernel.org/r/20250611224604.313496-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
When updating IRTEs in response to a GSI routing or IRQ bypass change,
pass the new/current routing information along with the associated irqfd.
This will allow KVM x86 to harden, simplify, and deduplicate its code.
Since adding/removing a bypass producer is now conveniently protected with
irqfds.lock, i.e. can't run concurrently with kvm_irq_routing_update(),
use the routing information cached in the irqfd instead of looking up
the information in the current GSI routing tables.
Opportunistically convert an existing printk() to pr_info() and put its
string onto a single line (old code that strictly adhered to 80 chars).
Link: https://lore.kernel.org/r/20250611224604.313496-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Add a helper to allocate and initialize an MSR or I/O permissions map, as
the logic is identical between the two map types, the only difference is
the size of the bitmap. Opportunistically add a comment to explain why
the bitmaps are initialized with 0xff, e.g. instead of the more common
zero-initialized behavior, which is the main motivation for deduplicating
the code.
No functional change intended.
Link: https://lore.kernel.org/r/20250610225737.156318-31-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Return -EINVAL instead of MSR_INVALID from svm_msrpm_bit_nr() to indicate
that the MSR isn't covered by one of the (currently) three MSRPM ranges,
and delete the MSR_INVALID macro now that all users are gone.
Link: https://lore.kernel.org/r/20250610225737.156318-29-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Store KVM's MSRPM pointers as "void *" instead of "u32 *" to guard against
directly accessing the bitmaps outside of code that is explicitly written
to access the bitmaps with a specific type.
Opportunistically use svm_vcpu_free_msrpm() in svm_vcpu_free() instead of
open coding an equivalent.
Link: https://lore.kernel.org/r/20250610225737.156318-27-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Move svm_msrpm_offset() from svm.c to nested.c now that all usage of the
u32-index offsets is nested virtualization specific.
No functional change intended.
Link: https://lore.kernel.org/r/20250610225737.156318-26-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
On a userspace MSR filter change, recalculate all MSR intercepts using the
filter-agnostic logic instead of maintaining a "shadow copy" of KVM's
desired intercepts. The shadow bitmaps add yet another point of failure,
are confusing (e.g. what does "handled specially" mean!?!?), an eyesore,
and a maintenance burden.
Given that KVM *must* be able to recalculate the correct intercepts at any
given time, and that MSR filter updates are not hot paths, there is zero
benefit to maintaining the shadow bitmaps.
Opportunistically switch from boot_cpu_has() to cpu_feature_enabled() as
appropriate.
Link: https://lore.kernel.org/all/aCdPbZiYmtni4Bjs@google.com
Link: https://lore.kernel.org/all/20241126180253.GAZ0YNTdXH1UGeqsu6@fat_crate.local
Cc: Francesco Lavra <francescolavra.fl@gmail.com>
Link: https://lore.kernel.org/r/20250610225737.156318-20-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Add and use SVM MSR interception APIs (in most paths) to match VMX's
APIs and nomenclature. Specifically, add SVM variants of:
vmx_disable_intercept_for_msr(vcpu, msr, type)
vmx_enable_intercept_for_msr(vcpu, msr, type)
vmx_set_intercept_for_msr(vcpu, msr, type, intercept)
to eventually replace SVM's single helper:
set_msr_interception(vcpu, msrpm, msr, allow_read, allow_write)
which is awkward to use (in all cases, KVM either applies the same logic
for both reads and writes, or intercepts one of read or write), and is
unintuitive due to using '0' to indicate interception should be *set*.
Keep the guts of the old API for the moment to avoid churning the MSR
filter code, as that mess will be overhauled in the near future. Leave
behind a temporary comment to call out that the shadow bitmaps have
inverted polarity relative to the bitmaps consumed by hardware.
No functional change intended.
Reviewed-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Link: https://lore.kernel.org/r/20250610225737.156318-15-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Add macro-built helpers for testing, setting, and clearing MSRPM entries
without relying on precomputed offsets. This sets the stage for eventually
removing general KVM use of precomputed offsets, which are quite confusing
and rather inefficient for the vast majority of KVM's usage.
Outside of merging L0 and L1 bitmaps for nested SVM, using u32-indexed
offsets and accesses is at best unnecessary, and at worst introduces extra
operations to retrieve the individual bit from within the offset u32 value.
And simply calling them "offsets" is very confusing, as the "unit" of the
offset isn't immediately obvious.
Use the new helpers in set_msr_interception_bitmap() and
msr_write_intercepted() to verify the math and operations, but keep the
existing offset-based logic in set_msr_interception_bitmap() to sanity
check the "clear" and "set" operations. Manipulating MSR interceptions
isn't a hot path and no kernel release is ever expected to contain this
specific version of set_msr_interception_bitmap() (it will be removed
entirely in the near future).
Link: https://lore.kernel.org/r/20250610225737.156318-14-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Don't initialize vmcb02's MSRPM with KVM's set of "always passthrough"
MSRs, as KVM always needs to consult L1's intercepts, i.e. needs to merge
vmcb01 with vmcb12 and write the result to vmcb02. This will eventually
allow for the removal of svm_vcpu_init_msrpm().
Note, the bitmaps are truly initialized by svm_vcpu_alloc_msrpm() (default
to intercepting all MSRs), e.g. if there is a bug lurking elsewhere, the
worst case scenario from dropping the call to svm_vcpu_init_msrpm() should
be that KVM would fail to passthrough MSRs to L2.
Link: https://lore.kernel.org/r/20250610225737.156318-13-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Use a dedicated array of MSRPM offsets to merge L0 and L1 bitmaps, i.e. to
merge KVM's vmcb01 bitmap with L1's vmcb12 bitmap. This will eventually
allow for the removal of direct_access_msrs, as the only path where
tracking the offsets is truly justified is the merge for nested SVM, where
merging in chunks is an easy way to batch uaccess reads/writes.
Opportunistically omit the x2APIC MSRs from the merge-specific array
instead of filtering them out at runtime.
Note, disabling interception of DEBUGCTL, XSS, EFER, PAT, GHCB, and
TSC_AUX is mutually exclusive with nested virtualization, as KVM passes
through those MSRs only for SEV-ES guests, and KVM doesn't support nested
virtualization for SEV+ guests. Defer removing those MSRs to a future
cleanup in order to make this refactoring as benign as possible.
Link: https://lore.kernel.org/r/20250610225737.156318-11-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Move SVM's MSR Permissions Map macros to svm.h in anticipation of adding
helpers that are available to SVM code, and opportunistically replace a
variety of open-coded literals with (hopefully) informative macros.
Opportunistically open code ARRAY_SIZE(msrpm_ranges) instead of wrapping
it as NUM_MSR_MAPS, which is an ambiguous name even if it were qualified
with "SVM_MSRPM".
Deliberately leave the ranges as open coded literals, as using macros to
define the ranges actually introduces more potential failure points, since
both the definitions and the usage have to be careful to use the correct
index. The lack of clear intent behind the ranges will be addressed in
future patches.
No functional change intended.
Link: https://lore.kernel.org/r/20250610225737.156318-10-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Drop the unnecessary and dangerous value-terminated behavior of
direct_access_msrs, and simply iterate over the actual size of the array.
The use in svm_set_x2apic_msr_interception() is especially sketchy, as it
relies on unused capacity being zero-initialized, and '0' being outside
the range of x2APIC MSRs.
To ensure the array and shadow_msr_intercept stay synchronized, simply
assert that their sizes are identical (note the six 64-bit-only MSRs).
Note, direct_access_msrs will soon be removed entirely; keeping the assert
synchronized with the array isn't expected to be along-term maintenance
burden.
Reviewed-by: Chao Gao <chao.gao@intel.com>
Link: https://lore.kernel.org/r/20250610225737.156318-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
- Wait for target vCPU to acknowledge KVM_REQ_UPDATE_PROTECTED_GUEST_STATE to
fix a race between AP destroy and VMRUN.
- Decrypt and dump the VMSA in dump_vmcb() if debugging enabled for the VM.
- Add support for ALLOWED_SEV_FEATURES.
- Add #VMGEXIT to the set of handlers special cased for CONFIG_RETPOLINE=y.
- Treat DEBUGCTL[5:2] as reserved to pave the way for virtualizing features
that utilize those bits.
- Don't account temporary allocations in sev_send_update_data().
- Add support for KVM_CAP_X86_BUS_LOCK_EXIT on SVM, via Bus Lock Threshold.
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Merge tag 'kvm-x86-svm-6.16' of https://github.com/kvm-x86/linux into HEAD
KVM SVM changes for 6.16:
- Wait for target vCPU to acknowledge KVM_REQ_UPDATE_PROTECTED_GUEST_STATE to
fix a race between AP destroy and VMRUN.
- Decrypt and dump the VMSA in dump_vmcb() if debugging enabled for the VM.
- Add support for ALLOWED_SEV_FEATURES.
- Add #VMGEXIT to the set of handlers special cased for CONFIG_RETPOLINE=y.
- Treat DEBUGCTL[5:2] as reserved to pave the way for virtualizing features
that utilize those bits.
- Don't account temporary allocations in sev_send_update_data().
- Add support for KVM_CAP_X86_BUS_LOCK_EXIT on SVM, via Bus Lock Threshold.
- Unify virtualization of IBRS on nested VM-Exit, and cross-vCPU IBPB, between
SVM and VMX.
- Advertise support to userspace for WRMSRNS and PREFETCHI.
- Rescan I/O APIC routes after handling EOI that needed to be intercepted due
to the old/previous routing, but not the new/current routing.
- Add a module param to control and enumerate support for device posted
interrupts.
- Misc cleanups.
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Merge tag 'kvm-x86-misc-6.16' of https://github.com/kvm-x86/linux into HEAD
KVM x86 misc changes for 6.16:
- Unify virtualization of IBRS on nested VM-Exit, and cross-vCPU IBPB, between
SVM and VMX.
- Advertise support to userspace for WRMSRNS and PREFETCHI.
- Rescan I/O APIC routes after handling EOI that needed to be intercepted due
to the old/previous routing, but not the new/current routing.
- Add a module param to control and enumerate support for device posted
interrupts.
- Misc cleanups.
Add support for KVM_CAP_X86_BUS_LOCK_EXIT on SVM CPUs with Bus Lock
Threshold, which is close enough to VMX's Bus Lock Detection VM-Exit to
allow reusing KVM_CAP_X86_BUS_LOCK_EXIT.
The biggest difference between the two features is that Threshold is
fault-like, whereas Detection is trap-like. To allow the guest to make
forward progress, Threshold provides a per-VMCB counter which is
decremented every time a bus lock occurs, and a VM-Exit is triggered if
and only if the counter is '0'.
To provide Detection-like semantics, initialize the counter to '0', i.e.
exit on every bus lock, and when re-executing the guilty instruction, set
the counter to '1' to effectively step past the instruction.
Note, in the unlikely scenario that re-executing the instruction doesn't
trigger a bus lock, e.g. because the guest has changed memory types or
patched the guilty instruction, the bus lock counter will be left at '1',
i.e. the guest will be able to do a bus lock on a different instruction.
In a perfect world, KVM would ensure the counter is '0' if the guest has
made forward progress, e.g. if RIP has changed. But trying to close that
hole would incur non-trivial complexity, for marginal benefit; the intent
of KVM_CAP_X86_BUS_LOCK_EXIT is to allow userspace rate-limit bus locks,
not to allow for precise detection of problematic guest code. And, it's
simply not feasible to fully close the hole, e.g. if an interrupt arrives
before the original instruction can re-execute, the guest could step past
a different bus lock.
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Manali Shukla <manali.shukla@amd.com>
Link: https://lore.kernel.org/r/20250502050346.14274-5-manali.shukla@amd.com
[sean: fix typo in comment]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Set the magic BP_SPEC_REDUCE bit to mitigate SRSO when running VMs if and
only if KVM has at least one active VM. Leaving the bit set at all times
unfortunately degrades performance by a wee bit more than expected.
Use a dedicated spinlock and counter instead of hooking virtualization
enablement, as changing the behavior of kvm.enable_virt_at_load based on
SRSO_BP_SPEC_REDUCE is painful, and has its own drawbacks, e.g. could
result in performance issues for flows that are sensitive to VM creation
latency.
Defer setting BP_SPEC_REDUCE until VMRUN is imminent to avoid impacting
performance on CPUs that aren't running VMs, e.g. if a setup is using
housekeeping CPUs. Setting BP_SPEC_REDUCE in task context, i.e. without
blasting IPIs to all CPUs, also helps avoid serializing 1<=>N transitions
without incurring a gross amount of complexity (see the Link for details
on how ugly coordinating via IPIs gets).
Link: https://lore.kernel.org/all/aBOnzNCngyS_pQIW@google.com
Fixes: 8442df2b49 ("x86/bugs: KVM: Add support for SRSO_MSR_FIX")
Reported-by: Michael Larabel <Michael@michaellarabel.com>
Closes: https://www.phoronix.com/review/linux-615-amd-regression
Cc: Borislav Petkov <bp@alien8.de>
Tested-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20250505180300.973137-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Both SVM and VMX have similar implementation for executing an IBPB
between running different vCPUs on the same CPU to create separate
prediction domains for different vCPUs.
For VMX, when the currently loaded VMCS is changed in
vmx_vcpu_load_vmcs(), an IBPB is executed if there is no 'buddy', which
is the case on vCPU load. The intention is to execute an IBPB when
switching vCPUs, but not when switching the VMCS within the same vCPU.
Executing an IBPB on nested transitions within the same vCPU is handled
separately and conditionally in nested_vmx_vmexit().
For SVM, the current VMCB is tracked on vCPU load and an IBPB is
executed when it is changed. The intention is also to execute an IBPB
when switching vCPUs, although it is possible that in some cases an IBBP
is executed when switching VMCBs for the same vCPU. Executing an IBPB on
nested transitions should be handled separately, and is proposed at [1].
Unify the logic by tracking the last loaded vCPU and execuintg the IBPB
on vCPU change in kvm_arch_vcpu_load() instead. When a vCPU is
destroyed, make sure all references to it are removed from any CPU. This
is similar to how SVM clears the current_vmcb tracking on vCPU
destruction. Remove the current VMCB tracking in SVM as it is no longer
required, as well as the 'buddy' parameter to vmx_vcpu_load_vmcs().
[1] https://lore.kernel.org/lkml/20250221163352.3818347-4-yosry.ahmed@linux.dev
Link: https://lore.kernel.org/all/20250320013759.3965869-1-yosry.ahmed@linux.dev
Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
[sean: tweak comment to stay at/under 80 columns]
Signed-off-by: Sean Christopherson <seanjc@google.com>
An SEV-ES/SEV-SNP VM save area (VMSA) can be decrypted if the guest
policy allows debugging. Update the dump_vmcb() routine to output
some of the SEV VMSA contents if possible. This can be useful for
debug purposes.
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Kim Phillips <kim.phillips@amd.com>
Link: https://lore.kernel.org/r/ea3b852c295b6f4b200925ed6b6e2c90d9475e71.1742477213.git.thomas.lendacky@amd.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
- Ensure the PSP driver is initialized when both the PSP and KVM modules are
built-in (the initcall framework doesn't handle dependencies).
- Use long-term pins when registering encrypted memory regions, so that the
pages are migrated out of MIGRATE_CMA/ZONE_MOVABLE and don't lead to
excessive fragmentation.
- Add macros and helpers for setting GHCB return/error codes.
- Add support for Idle HLT interception, which elides interception if the vCPU
has a pending, unmasked virtual IRQ when HLT is executed.
- Fix a bug in INVPCID emulation where KVM fails to check for a non-canonical
address.
- Don't attempt VMRUN for SEV-ES+ guests if the vCPU's VMSA is invalid, e.g.
because the vCPU was "destroyed" via SNP's AP Creation hypercall.
- Reject SNP AP Creation if the requested SEV features for the vCPU don't
match the VM's configured set of features.
- Misc cleanups
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Merge tag 'kvm-x86-svm-6.15' of https://github.com/kvm-x86/linux into HEAD
KVM SVM changes for 6.15
- Ensure the PSP driver is initialized when both the PSP and KVM modules are
built-in (the initcall framework doesn't handle dependencies).
- Use long-term pins when registering encrypted memory regions, so that the
pages are migrated out of MIGRATE_CMA/ZONE_MOVABLE and don't lead to
excessive fragmentation.
- Add macros and helpers for setting GHCB return/error codes.
- Add support for Idle HLT interception, which elides interception if the vCPU
has a pending, unmasked virtual IRQ when HLT is executed.
- Fix a bug in INVPCID emulation where KVM fails to check for a non-canonical
address.
- Don't attempt VMRUN for SEV-ES+ guests if the vCPU's VMSA is invalid, e.g.
because the vCPU was "destroyed" via SNP's AP Creation hypercall.
- Reject SNP AP Creation if the requested SEV features for the vCPU don't
match the VM's configured set of features.
- Misc cleanups
Explicitly reject KVM_RUN with KVM_EXIT_FAIL_ENTRY if userspace "coerces"
KVM into running an SEV-ES+ guest with an invalid VMSA, e.g. by modifying
a vCPU's mp_state to be RUNNABLE after an SNP vCPU has undergone a Destroy
event. On Destroy or failed Create, KVM marks the vCPU HALTED so that
*KVM* doesn't run the vCPU, but nothing prevents a misbehaving VMM from
manually making the vCPU RUNNABLE via KVM_SET_MP_STATE.
Attempting VMRUN with an invalid VMSA should be harmless, but knowingly
executing VMRUN with bad control state is at best dodgy.
Fixes: e366f92ea9 ("KVM: SEV: Support SEV-SNP AP Creation NAE event")
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@amd.com>
Link: https://lore.kernel.org/r/20250227012541.3234589-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Mark BTF as reserved in DEBUGCTL on AMD, as KVM doesn't actually support
BTF, and fully enabling BTF virtualization is non-trivial due to
interactions with the emulator, guest_debug, #DB interception, nested SVM,
etc.
Don't inject #GP if the guest attempts to set BTF, as there's no way to
communicate lack of support to the guest, and instead suppress the flag
and treat the WRMSR as (partially) unsupported.
In short, make KVM behave the same on AMD and Intel (VMX already squashes
BTF).
Note, due to other bugs in KVM's handling of DEBUGCTL, the only way BTF
has "worked" in any capacity is if the guest simultaneously enables LBRs.
Reported-by: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: stable@vger.kernel.org
Reviewed-and-tested-by: Ravi Bangoria <ravi.bangoria@amd.com>
Link: https://lore.kernel.org/r/20250227222411.3490595-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Drop bits 5:2 from the guest's effective DEBUGCTL value, as AMD changed
the architectural behavior of the bits and broke backwards compatibility.
On CPUs without BusLockTrap (or at least, in APMs from before ~2023),
bits 5:2 controlled the behavior of external pins:
Performance-Monitoring/Breakpoint Pin-Control (PBi)—Bits 5:2, read/write.
Software uses thesebits to control the type of information reported by
the four external performance-monitoring/breakpoint pins on the
processor. When a PBi bit is cleared to 0, the corresponding external pin
(BPi) reports performance-monitor information. When a PBi bit is set to
1, the corresponding external pin (BPi) reports breakpoint information.
With the introduction of BusLockTrap, presumably to be compatible with
Intel CPUs, AMD redefined bit 2 to be BLCKDB:
Bus Lock #DB Trap (BLCKDB)—Bit 2, read/write. Software sets this bit to
enable generation of a #DB trap following successful execution of a bus
lock when CPL is > 0.
and redefined bits 5:3 (and bit 6) as "6:3 Reserved MBZ".
Ideally, KVM would treat bits 5:2 as reserved. Defer that change to a
feature cleanup to avoid breaking existing guest in LTS kernels. For now,
drop the bits to retain backwards compatibility (of a sort).
Note, dropping bits 5:2 is still a guest-visible change, e.g. if the guest
is enabling LBRs *and* the legacy PBi bits, then the state of the PBi bits
is visible to the guest, whereas now the guest will always see '0'.
Reported-by: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: stable@vger.kernel.org
Reviewed-and-tested-by: Ravi Bangoria <ravi.bangoria@amd.com>
Link: https://lore.kernel.org/r/20250227222411.3490595-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Provide helpers to set the error code when converting VMGEXIT SW_EXITINFO1 and
SW_EXITINFO2 codes from plain numbers to proper defines. Add comments for
better code readability.
No functionality changed.
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Melody Wang <huibo.wang@amd.com>
Link: https://lore.kernel.org/r/20250225213937.2471419-3-huibo.wang@amd.com
[sean: tweak comments, fix formatting goofs]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Simplify code by replacing &to_kvm_svm(kvm)->sev_info with
to_kvm_sev_info() helper function. Wherever possible, drop the local
variable declaration and directly use the helper instead.
No functional changes.
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Reviewed-by: Pavan Kumar Paluri <papaluri@amd.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@amd.com>
Link: https://lore.kernel.org/r/20250123055140.144378-1-nikunj@amd.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
- Overhaul KVM's CPUID feature infrastructure to replace "governed" features
with per-vCPU tracking of the vCPU's capabailities for all features. Along
the way, refactor the code to make it easier to add/modify features, and
add a variety of self-documenting macro types to again simplify adding new
features and to help readers understand KVM's handling of existing features.
- Rework KVM's handling of VM-Exits during event vectoring to plug holes where
KVM unintentionally puts the vCPU into infinite loops in some scenarios,
e.g. if emulation is triggered by the exit, and to bring parity between VMX
and SVM.
- Add pending request and interrupt injection information to the kvm_exit and
kvm_entry tracepoints respectively.
- Fix a relatively benign flaw where KVM would end up redoing RDPKRU when
loading guest/host PKRU due to a refactoring of the kernel helpers that
didn't account for KVM's pre-checking of the need to do WRPKRU.
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Merge tag 'kvm-x86-misc-6.14' of https://github.com/kvm-x86/linux into HEAD
KVM x86 misc changes for 6.14:
- Overhaul KVM's CPUID feature infrastructure to track all vCPU capabilities
instead of just those where KVM needs to manage state and/or explicitly
enable the feature in hardware. Along the way, refactor the code to make
it easier to add features, and to make it more self-documenting how KVM
is handling each feature.
- Rework KVM's handling of VM-Exits during event vectoring; this plugs holes
where KVM unintentionally puts the vCPU into infinite loops in some scenarios
(e.g. if emulation is triggered by the exit), and brings parity between VMX
and SVM.
- Add pending request and interrupt injection information to the kvm_exit and
kvm_entry tracepoints respectively.
- Fix a relatively benign flaw where KVM would end up redoing RDPKRU when
loading guest/host PKRU, due to a refactoring of the kernel helpers that
didn't account for KVM's pre-checking of the need to do WRPKRU.
As the first step toward replacing KVM's so-called "governed features"
framework with a more comprehensive, less poorly named implementation,
replace the "kvm_governed_feature" function prefix with "guest_cpu_cap"
and rename guest_can_use() to guest_cpu_cap_has().
The "guest_cpu_cap" naming scheme mirrors that of "kvm_cpu_cap", and
provides a more clear distinction between guest capabilities, which are
KVM controlled (heh, or one might say "governed"), and guest CPUID, which
with few exceptions is fully userspace controlled.
Opportunistically rewrite the comment about XSS passthrough for SEV-ES
guests to avoid referencing so many functions, as such comments are prone
to becoming stale (case in point...).
No functional change intended.
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Link: https://lore.kernel.org/r/20241128013424.4096668-40-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Define sev_{,es_,snp_}guest() as "false" when SEV is disabled via Kconfig,
i.e. when CONFIG_KVM_AMD_SEV=n. Despite the helpers being __always_inline,
gcc-12 is somehow incapable of realizing that the return value is a
compile-time constant and generates sub-optimal code.
Opportunistically clump the paths together to reduce the amount of
ifdeffery.
No functional change intended.
Link: https://lore.kernel.org/r/20241127234659.4046347-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
The host save area is a VMCB, track it as such to help readers follow
along, but mostly to cleanup/simplify the retrieval of the SEV-ES host
save area.
Note, the compile-time assertion that
offsetof(struct vmcb, save) == EXPECTED_VMCB_CONTROL_AREA_SIZE
ensures that the SEV-ES save area is indeed at offset 0x400 (whoever added
the expected/architectural VMCB offsets apparently likes decimal).
No functional change intended.
Link: https://lore.kernel.org/r/20240802204511.352017-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Add __sme_pa_to_page() to pair with __sme_page_pa() and use it to replace
open coded equivalents, including for "iopm_base", which previously
avoided having to do __sme_clr() by storing the raw PA in the global
variable.
Opportunistically convert __sme_page_pa() to a helper to provide type
safety.
No functional change intended.
Link: https://lore.kernel.org/r/20240802204511.352017-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
The GHCB 2.0 specification defines 2 GHCB request types to allow SNP guests
to send encrypted messages/requests to firmware: SNP Guest Requests and SNP
Extended Guest Requests. These encrypted messages are used for things like
servicing attestation requests issued by the guest. Implementing support for
these is required to be fully GHCB-compliant.
For the most part, KVM only needs to handle forwarding these requests to
firmware (to be issued via the SNP_GUEST_REQUEST firmware command defined
in the SEV-SNP Firmware ABI), and then forwarding the encrypted response to
the guest.
However, in the case of SNP Extended Guest Requests, the host is also
able to provide the certificate data corresponding to the endorsement key
used by firmware to sign attestation report requests. This certificate data
is provided by userspace because:
1) It allows for different keys/key types to be used for each particular
guest with requiring any sort of KVM API to configure the certificate
table in advance on a per-guest basis.
2) It provides additional flexibility with how attestation requests might
be handled during live migration where the certificate data for
source/dest might be different.
3) It allows all synchronization between certificates and firmware/signing
key updates to be handled purely by userspace rather than requiring
some in-kernel mechanism to facilitate it. [1]
To support fetching certificate data from userspace, a new KVM exit type will
be needed to handle fetching the certificate from userspace. An attempt to
define a new KVM_EXIT_COCO/KVM_EXIT_COCO_REQ_CERTS exit type to handle this
was introduced in v1 of this patchset, but is still being discussed by
community, so for now this patchset only implements a stub version of SNP
Extended Guest Requests that does not provide certificate data, but is still
enough to provide compliance with the GHCB 2.0 spec.
Version 2 of GHCB specification added support for the SNP Guest Request
Message NAE event. The event allows for an SEV-SNP guest to make
requests to the SEV-SNP firmware through the hypervisor using the
SNP_GUEST_REQUEST API defined in the SEV-SNP firmware specification.
This is used by guests primarily to request attestation reports from
firmware. There are other request types are available as well, but the
specifics of what guest requests are being made generally does not
affect how they are handled by the hypervisor, which only serves as a
proxy for the guest requests and firmware responses.
Implement handling for these events.
When an SNP Guest Request is issued, the guest will provide its own
request/response pages, which could in theory be passed along directly
to firmware. However, these pages would need special care:
- Both pages are from shared guest memory, so they need to be
protected from migration/etc. occurring while firmware reads/writes
to them. At a minimum, this requires elevating the ref counts and
potentially needing an explicit pinning of the memory. This places
additional restrictions on what type of memory backends userspace
can use for shared guest memory since there would be some reliance
on using refcounted pages.
- The response page needs to be switched to Firmware-owned state
before the firmware can write to it, which can lead to potential
host RMP #PFs if the guest is misbehaved and hands the host a
guest page that KVM is writing to for other reasons (e.g. virtio
buffers).
Both of these issues can be avoided completely by using
separately-allocated bounce pages for both the request/response pages
and passing those to firmware instead. So that's the approach taken
here.
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Co-developed-by: Alexey Kardashevskiy <aik@amd.com>
Signed-off-by: Alexey Kardashevskiy <aik@amd.com>
Co-developed-by: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
[mdr: ensure FW command failures are indicated to guest, drop extended
request handling to be re-written as separate patch, massage commit]
Signed-off-by: Michael Roth <michael.roth@amd.com>
Message-ID: <20240701223148.3798365-2-michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
- Make per-CPU save_area allocations NUMA-aware.
- Force sev_es_host_save_area() to be inlined to avoid calling into an
instrumentable function from noinstr code.
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Merge tag 'kvm-x86-svm-6.11' of https://github.com/kvm-x86/linux into HEAD
KVM SVM changes for 6.11
- Make per-CPU save_area allocations NUMA-aware.
- Force sev_es_host_save_area() to be inlined to avoid calling into an
instrumentable function from noinstr code.
- Add a global struct to consolidate tracking of host values, e.g. EFER, and
move "shadow_phys_bits" into the structure as "maxphyaddr".
- Add KVM_CAP_X86_APIC_BUS_CYCLES_NS to allow configuring the effective APIC
bus frequency, because TDX.
- Print the name of the APICv/AVIC inhibits in the relevant tracepoint.
- Clean up KVM's handling of vendor specific emulation to consistently act on
"compatible with Intel/AMD", versus checking for a specific vendor.
- Misc cleanups
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Merge tag 'kvm-x86-misc-6.11' of https://github.com/kvm-x86/linux into HEAD
KVM x86 misc changes for 6.11
- Add a global struct to consolidate tracking of host values, e.g. EFER, and
move "shadow_phys_bits" into the structure as "maxphyaddr".
- Add KVM_CAP_X86_APIC_BUS_CYCLES_NS to allow configuring the effective APIC
bus frequency, because TDX.
- Print the name of the APICv/AVIC inhibits in the relevant tracepoint.
- Clean up KVM's handling of vendor specific emulation to consistently act on
"compatible with Intel/AMD", versus checking for a specific vendor.
- Misc cleanups
Keep kvm_apicv_inhibit enum naming consistent with the current pattern by
renaming the reason/enumerator defined as APICV_INHIBIT_REASON_DISABLE to
APICV_INHIBIT_REASON_DISABLED.
No functional change intended.
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Link: https://lore.kernel.org/r/20240506225321.3440701-3-alejandro.j.jimenez@oracle.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
save_area of per-CPU svm_data are dominantly accessed from their
own local CPUs, so allocate them node-local for performance reason
so rename __snp_safe_alloc_page as snp_safe_alloc_page_node which
accepts numa node id as input parameter, svm_cpu_init call it with
node id switched from cpu id
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20240520120858.13117-4-lirongqing@baidu.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
The allocation for the per-CPU save area in svm_cpu_init shouldn't
be accounted, So introduce __snp_safe_alloc_page helper, which has
gfp flag as input, svm_cpu_init calls __snp_safe_alloc_page with
GFP_KERNEL, snp_safe_alloc_page calls __snp_safe_alloc_page with
GFP_KERNEL_ACCOUNT as input
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20240520120858.13117-3-lirongqing@baidu.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
The input parameter 'vcpu' in snp_safe_alloc_page is not used.
Therefore, remove it.
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20240520120858.13117-2-lirongqing@baidu.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Pull base x86 KVM support for running SEV-SNP guests from Michael Roth:
* add some basic infrastructure and introduces a new KVM_X86_SNP_VM
vm_type to handle differences versus the existing KVM_X86_SEV_VM and
KVM_X86_SEV_ES_VM types.
* implement the KVM API to handle the creation of a cryptographic
launch context, encrypt/measure the initial image into guest memory,
and finalize it before launching it.
* implement handling for various guest-generated events such as page
state changes, onlining of additional vCPUs, etc.
* implement the gmem/mmu hooks needed to prepare gmem-allocated pages
before mapping them into guest private memory ranges as well as
cleaning them up prior to returning them to the host for use as
normal memory. Because those cleanup hooks supplant certain
activities like issuing WBINVDs during KVM MMU invalidations, avoid
duplicating that work to avoid unecessary overhead.
This merge leaves out support support for attestation guest requests
and for loading the signing keys to be used for attestation requests.
As documented in APM[1], LBR Virtualization must be enabled for SEV-ES
guests. Although KVM currently enforces LBRV for SEV-ES guests, there
are multiple issues with it:
o MSR_IA32_DEBUGCTLMSR is still intercepted. Since MSR_IA32_DEBUGCTLMSR
interception is used to dynamically toggle LBRV for performance reasons,
this can be fatal for SEV-ES guests. For ex SEV-ES guest on Zen3:
[guest ~]# wrmsr 0x1d9 0x4
KVM: entry failed, hardware error 0xffffffff
EAX=00000004 EBX=00000000 ECX=000001d9 EDX=00000000
Fix this by never intercepting MSR_IA32_DEBUGCTLMSR for SEV-ES guests.
No additional save/restore logic is required since MSR_IA32_DEBUGCTLMSR
is of swap type A.
o KVM will disable LBRV if userspace sets MSR_IA32_DEBUGCTLMSR before the
VMSA is encrypted. Fix this by moving LBRV enablement code post VMSA
encryption.
[1]: AMD64 Architecture Programmer's Manual Pub. 40332, Rev. 4.07 - June
2023, Vol 2, 15.35.2 Enabling SEV-ES.
https://bugzilla.kernel.org/attachment.cgi?id=304653
Fixes: 376c6d2850 ("KVM: SVM: Provide support for SEV-ES vCPU creation/loading")
Co-developed-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
Message-ID: <20240531044644.768-4-ravi.bangoria@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
