the new simple faux bus
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Merge tag 'x86_microcode_for_v6.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 microcode loader update from Borislav Petkov:
- Switch the microcode loader from using the fake platform device to
the new simple faux bus
* tag 'x86_microcode_for_v6.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/microcode: Move away from using a fake platform device
Downloading firmware needs a device to hang off of, and so a platform device
seemed like the simplest way to do this. Now that we have a faux device
interface, use that instead as this "microcode device" is not anything
resembling a platform device at all.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/2025070121-omission-small-9308@gregkh
In order to let all the APIs under <cpuid/api.h> have a shared "cpuid_"
namespace, rename have_cpuid_p() to cpuid_feature().
Adjust all call-sites accordingly.
Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: x86-cpuid@lists.linux.dev
Link: https://lore.kernel.org/r/20250508150240.172915-4-darwi@linutronix.de
Prepare to resolve conflicts with an upstream series of fixes that conflict
with pending x86 changes:
6f5bf947ba Merge tag 'its-for-linus-20250509' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Consolidate the whole logic which determines whether the microcode loader
should be enabled or not into a single function and call it everywhere.
Well, almost everywhere - not in mk_early_pgtbl_32() because there the kernel
is running without paging enabled and checking dis_ucode_ldr et al would
require physical addresses and uglification of the code.
But since this is 32-bit, the easier thing to do is to simply map the initrd
unconditionally especially since that mapping is getting removed later anyway
by zap_early_initrd_mapping() and avoid the uglification.
In doing so, address the issue of old 486er machines without CPUID
support, not booting current kernels.
[ mingo: Fix no previous prototype for ‘microcode_loader_disabled’ [-Wmissing-prototypes] ]
Fixes: 4c585af718 ("x86/boot/32: Temporarily map initrd for microcode loading")
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@kernel.org>
Link: https://lore.kernel.org/r/CANpbe9Wm3z8fy9HbgS8cuhoj0TREYEEkBipDuhgkWFvqX0UoVQ@mail.gmail.com
For historic reasons there are some TSC-related functions in the
<asm/msr.h> header, even though there's an <asm/tsc.h> header.
To facilitate the relocation of rdtsc{,_ordered}() from <asm/msr.h>
to <asm/tsc.h> and to eventually eliminate the inclusion of
<asm/msr.h> in <asm/tsc.h>, add an explicit <asm/msr.h> dependency
to the source files that reference definitions from <asm/msr.h>.
[ mingo: Clarified the changelog. ]
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Uros Bizjak <ubizjak@gmail.com>
Link: https://lore.kernel.org/r/20250501054241.1245648-1-xin@zytor.com
After
6f059e634dcd("x86/microcode: Clarify the late load logic"),
if the load is up-to-date, the AMD side returns UCODE_OK which leads to
load_late_locked() returning -EBADFD.
Handle UCODE_OK in the switch case to avoid this error.
[ bp: Massage commit message. ]
Fixes: 6f059e634d ("x86/microcode: Clarify the late load logic")
Signed-off-by: Annie Li <jiayanli@google.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250430053424.77438-1-jiayanli@google.com
Old microcode is bad for users and for kernel developers.
For users, it exposes them to known fixed security and/or functional
issues. These obviously rarely result in instant dumpster fires in
every environment. But it is as important to keep your microcode up
to date as it is to keep your kernel up to date.
Old microcode also makes kernels harder to debug. A developer looking
at an oops need to consider kernel bugs, known CPU issues and unknown
CPU issues as possible causes. If they know the microcode is up to
date, they can mostly eliminate known CPU issues as the cause.
Make it easier to tell if CPU microcode is out of date. Add a list
of released microcode. If the loaded microcode is older than the
release, tell users in a place that folks can find it:
/sys/devices/system/cpu/vulnerabilities/old_microcode
Tell kernel kernel developers about it with the existing taint
flag:
TAINT_CPU_OUT_OF_SPEC
== Discussion ==
When a user reports a potential kernel issue, it is very common
to ask them to reproduce the issue on mainline. Running mainline,
they will (independently from the distro) acquire a more up-to-date
microcode version list. If their microcode is old, they will
get a warning about the taint and kernel developers can take that
into consideration when debugging.
Just like any other entry in "vulnerabilities/", users are free to
make their own assessment of their exposure.
== Microcode Revision Discussion ==
The microcode versions in the table were generated from the Intel
microcode git repo:
8ac9378a8487 ("microcode-20241112 Release")
which as of this writing lags behind the latest microcode-20250211.
It can be argued that the versions that the kernel picks to call "old"
should be a revision or two old. Which specific version is picked is
less important to me than picking *a* version and enforcing it.
This repository contains only microcode versions that Intel has deemed
to be OS-loadable. It is quite possible that the BIOS has loaded a
newer microcode than the latest in this repo. If this happens, the
system is considered to have new microcode, not old.
Specifically, the sysfs file and taint flag answer the question:
Is the CPU running on the latest OS-loadable microcode,
or something even later that the BIOS loaded?
In other words, Intel never publishes an authoritative list of CPUs
and latest microcode revisions. Until it does, this is the best that
Linux can do.
Also note that the "intel-ucode-defs.h" file is simple, ugly and
has lots of magic numbers. That's on purpose and should allow a
single file to be shared across lots of stable kernel regardless of if
they have the new "VFM" infrastructure or not. It was generated with
a dumb script.
== FAQ ==
Q: Does this tell me if my system is secure or insecure?
A: No. It only tells you if your microcode was old when the
system booted.
Q: Should the kernel warn if the microcode list itself is too old?
A: No. New kernels will get new microcode lists, both mainline
and stable. The only way to have an old list is to be running
an old kernel in which case you have bigger problems.
Q: Is this for security or functional issues?
A: Both.
Q: If a given microcode update only has functional problems but
no security issues, will it be considered old?
A: Yes. All microcode image versions within a microcode release
are treated identically. Intel appears to make security
updates without disclosing them in the release notes. Thus,
all updates are considered to be security-relevant.
Q: Who runs old microcode?
A: Anybody with an old distro. This happens all the time inside
of Intel where there are lots of weird systems in labs that
might not be getting regular distro updates and might also
be running rather exotic microcode images.
Q: If I update my microcode after booting will it stop saying
"Vulnerable"?
A: No. Just like all the other vulnerabilies, you need to
reboot before the kernel will reassess your vulnerability.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: "Ahmed S. Darwish" <darwi@linutronix.de>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/all/20250421195659.CF426C07%40davehans-spike.ostc.intel.com
(cherry picked from commit 9127865b15eb0a1bd05ad7efe29489c44394bdc1)
All Zen5 machines out there should get BIOS updates which update to the
correct microcode patches addressing the microcode signature issue.
However, silly people carve out random microcode blobs from BIOS
packages and think are doing other people a service this way...
Block loading of any unreleased standalone Zen5 microcode patches.
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: <stable@kernel.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Cc: Nikolay Borisov <nik.borisov@suse.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20250410114222.32523-1-bp@kernel.org
If microcode did not get loaded there is no reason to keep it in the cache.
Moreover, if loading failed it will not be possible to load an earlier version
of microcode since the failed revision will always be selected from the cache
on the next reload attempt.
Since the failed revisions is not easily available at this point just clean the
whole cache. It will be rebuilt later if needed.
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20250327230503.1850368-3-boris.ostrovsky@oracle.com
When verify_sha256_digest() fails, __apply_microcode_amd() should propagate
the failure by returning false (and not -1 which is promoted to true).
Fixes: 50cef76d5c ("x86/microcode/AMD: Load only SHA256-checksummed patches")
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250327230503.1850368-2-boris.ostrovsky@oracle.com
The Family model check to read the processor flag MSR is misleading and
potentially incorrect. It doesn't consider Family while comparing the
model number. The original check did have a Family number but it got
lost/moved during refactoring.
intel_collect_cpu_info() is called through multiple paths such as early
initialization, CPU hotplug as well as IFS image load. Some of these
flows would be error prone due to the ambiguous check.
Correct the processor flag scan check to use a Family number and update
it to a VFM based one to make it more readable.
Signed-off-by: Sohil Mehta <sohil.mehta@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/r/20250219184133.816753-4-sohil.mehta@intel.com
Currently, load_microcode_amd() iterates over all NUMA nodes, retrieves their
CPU masks and unconditionally accesses per-CPU data for the first CPU of each
mask.
According to Documentation/admin-guide/mm/numaperf.rst:
"Some memory may share the same node as a CPU, and others are provided as
memory only nodes."
Therefore, some node CPU masks may be empty and wouldn't have a "first CPU".
On a machine with far memory (and therefore CPU-less NUMA nodes):
- cpumask_of_node(nid) is 0
- cpumask_first(0) is CONFIG_NR_CPUS
- cpu_data(CONFIG_NR_CPUS) accesses the cpu_info per-CPU array at an
index that is 1 out of bounds
This does not have any security implications since flashing microcode is
a privileged operation but I believe this has reliability implications by
potentially corrupting memory while flashing a microcode update.
When booting with CONFIG_UBSAN_BOUNDS=y on an AMD machine that flashes
a microcode update. I get the following splat:
UBSAN: array-index-out-of-bounds in arch/x86/kernel/cpu/microcode/amd.c:X:Y
index 512 is out of range for type 'unsigned long[512]'
[...]
Call Trace:
dump_stack
__ubsan_handle_out_of_bounds
load_microcode_amd
request_microcode_amd
reload_store
kernfs_fop_write_iter
vfs_write
ksys_write
do_syscall_64
entry_SYSCALL_64_after_hwframe
Change the loop to go over only NUMA nodes which have CPUs before determining
whether the first CPU on the respective node needs microcode update.
[ bp: Massage commit message, fix typo. ]
Fixes: 7ff6edf4fe ("x86/microcode/AMD: Fix mixed steppings support")
Signed-off-by: Florent Revest <revest@chromium.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250310144243.861978-1-revest@chromium.org
Load patches for which the driver carries a SHA256 checksum of the patch
blob.
This can be disabled by adding "microcode.amd_sha_check=off" on the
kernel cmdline. But it is highly NOT recommended.
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Put the MSR_AMD64_PATCH_LEVEL reading of the current microcode revision
the hw has, into a separate function.
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20250211163648.30531-6-bp@kernel.org
Commit
a7939f0167 ("x86/microcode/amd: Cache builtin/initrd microcode early")
renamed it to save_microcode_in_initrd() and made it static. Zap the
forgotten declarations.
No functional changes.
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20250211163648.30531-3-bp@kernel.org
The result of that function is in essence boolean, so simplify to return the
result of the relevant expression. It also makes it follow the convention used
by __verify_patch_section().
No functional changes.
Signed-off-by: Nikolay Borisov <nik.borisov@suse.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20241018155151.702350-3-nik.borisov@suse.com
Instead of open-coding the check for size/data move it inside the
function and make it return a boolean indicating whether data was found
or not.
No functional changes.
[ bp: Write @ret in find_blobs_in_containers() only on success. ]
Signed-off-by: Nikolay Borisov <nik.borisov@suse.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20241018155151.702350-2-nik.borisov@suse.com
Due to specific requirements while applying microcode patches on Zen1
and 2, the patch buffer mapping needs to be flushed from the TLB after
application. Do so.
If not, unnecessary and unnatural delays happen in the boot process.
Reported-by: Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
Cc: <stable@kernel.org> # f1d84b59cb ("x86/mm: Carve out INVLPG inline asm for use by others")
Link: https://lore.kernel.org/r/ZyulbYuvrkshfsd2@antipodes
microcode patch on Intel as this was addressing a microcode bug for which
there is a concrete microcode revision check instead
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Merge tag 'x86_microcode_for_v6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 microcode loader update from Borislav Petkov:
- Remove the unconditional cache writeback and invalidation after
loading the microcode patch on Intel as this was addressing a
microcode bug for which there is a concrete microcode revision check
instead
* tag 'x86_microcode_for_v6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/microcode/intel: Remove unnecessary cache writeback and invalidation
Currently, an unconditional cache flush is performed during every
microcode update. Although the original changelog did not mention
a specific erratum, this measure was primarily intended to address
a specific microcode bug, the load of which has already been blocked by
is_blacklisted(). Therefore, this cache flush is no longer necessary.
Additionally, the side effects of doing this have been overlooked. It
increases CPU rendezvous time during late loading, where the cache flush
takes between 1x to 3.5x longer than the actual microcode update.
Remove native_wbinvd() and update the erratum name to align with the
latest errata documentation, document ID 334163 Version 022US.
[ bp: Zap the flaky documentation URL. ]
Fixes: 91df9fdf51 ("x86/microcode/intel: Writeback and invalidate caches before updating microcode")
Reported-by: Yan Hua Wu <yanhua1.wu@intel.com>
Reported-by: William Xie <william.xie@intel.com>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Ashok Raj <ashok.raj@intel.com>
Tested-by: Yan Hua Wu <yanhua1.wu@intel.com>
Link: https://lore.kernel.org/r/20241001161042.465584-2-chang.seok.bae@intel.com
This function should've been split a long time ago because it is used in
two paths:
1) On the late loading path, when the microcode is loaded through the
request_firmware interface
2) In the save_microcode_in_initrd() path which collects all the
microcode patches which are relevant for the current system before
the initrd with the microcode container has been jettisoned.
In that path, it is not really necessary to iterate over the nodes on
a system and match a patch however it didn't cause any trouble so it
was left for a later cleanup
However, that later cleanup was expedited by the fact that Jens was
enabling "Use L3 as a NUMA node" in the BIOS setting in his machine and
so this causes the NUMA CPU masks used in cpumask_of_node() to be
generated *after* 2) above happened on the first node. Which means, all
those masks were funky, wrong, uninitialized and whatnot, leading to
explosions when dereffing c->microcode in load_microcode_amd().
So split that function and do only the necessary work needed at each
stage.
Fixes: 94838d230a ("x86/microcode/AMD: Use the family,model,stepping encoded in the patch ID")
Reported-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/91194406-3fdf-4e38-9838-d334af538f74@kernel.dk
Commit in Fixes changed how a microcode patch is loaded on Zen and newer but
the patch matching needs to happen with different rigidity, depending on what
is being done:
1) When the patch is added to the patches cache, the stepping must be ignored
because the driver still supports different steppings per system
2) When the patch is matched for loading, then the stepping must be taken into
account because each CPU needs the patch matching its exact stepping
Take care of that by making the matching smarter.
Fixes: 94838d230a ("x86/microcode/AMD: Use the family,model,stepping encoded in the patch ID")
Reported-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/91194406-3fdf-4e38-9838-d334af538f74@kernel.dk
Initialize equiv_id in order to shut up:
arch/x86/kernel/cpu/microcode/amd.c:714:6: warning: variable 'equiv_id' is \
used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
if (x86_family(bsp_cpuid_1_eax) < 0x17) {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
because clang doesn't do interprocedural analysis for warnings to see
that this variable won't be used uninitialized.
Fixes: 94838d230a ("x86/microcode/AMD: Use the family,model,stepping encoded in the patch ID")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202407291815.gJBST0P3-lkp@intel.com/
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
On Zen and newer, the family, model and stepping is part of the
microcode patch ID so that the equivalence table the driver has been
using, is not needed anymore.
So switch the driver to use that from now on.
The equivalence table in the microcode blob should still remain in case
there's need to pass some additional information to the kernel loader.
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240725112037.GBZqI1BbUk1KMlOJ_D@fat_crate.local
New CPU #defines encode vendor and family as well as model.
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/all/20240424181513.41829-1-tony.luck%40intel.com
Older versions of clang show a warning for amd.c after a fix for a gcc
warning:
arch/x86/kernel/cpu/microcode/amd.c:478:47: error: format specifies type \
'unsigned char' but the argument has type 'u16' (aka 'unsigned short') [-Werror,-Wformat]
"amd-ucode/microcode_amd_fam%02hhxh.bin", family);
~~~~~~ ^~~~~~
%02hx
In clang-16 and higher, this warning is disabled by default, but clang-15 is
still supported, and it's trivial to avoid by adapting the types according
to the range of the passed data and the format string.
[ bp: Massage commit message. ]
Fixes: 2e9064facc ("x86/microcode/amd: Fix snprintf() format string warning in W=1 build")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240405204919.1003409-1-arnd@kernel.org
Now that __num_cores_per_package and __num_threads_per_package are
available, cpuinfo::x86_max_cores and the related math all over the place
can be replaced with the ready to consume data.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240213210253.176147806@linutronix.de
This was meant to be done only when early microcode got updated
successfully. Move it into the if-branch.
Also, make sure the current revision is read unconditionally and only
once.
Fixes: 080990aa33 ("x86/microcode: Rework early revisions reporting")
Reported-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Ashok Raj <ashok.raj@intel.com>
Link: https://lore.kernel.org/r/ZWjVt5dNRjbcvlzR@a4bf019067fa.jf.intel.com
After successful update, the late loading routine prints an update
summary similar to:
microcode: load: updated on 128 primary CPUs with 128 siblings
microcode: revision: 0x21000170 -> 0x21000190
Remove the redundant message in the Intel side of the driver.
[ bp: Massage commit message. ]
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/ZWjYhedNfhAUmt0k@a4bf019067fa.jf.intel.com
The AMD side of the loader issues the microcode revision for each
logical thread on the system, which can become really noisy on huge
machines. And doing that doesn't make a whole lot of sense - the
microcode revision is already in /proc/cpuinfo.
So in case one is interested in the theoretical support of mixed silicon
steppings on AMD, one can check there.
What is also missing on the AMD side - something which people have
requested before - is showing the microcode revision the CPU had
*before* the early update.
So abstract that up in the main code and have the BSP on each vendor
provide those revision numbers.
Then, dump them only once on driver init.
On Intel, do not dump the patch date - it is not needed.
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/CAHk-=wg=%2B8rceshMkB4VnKxmRccVLtBLPBawnewZuuqyx5U=3A@mail.gmail.com
First of all, the print is useless. The driver will either load and say
which microcode revision the machine has or issue an error.
Then, the version number is meaningless and actively confusing, as Yazen
mentioned recently: when a subset of patches are backported to a distro
kernel, one can't assume the driver version is the same as the upstream
one. And besides, the version number of the loader hasn't been used and
incremented for a long time. So drop it.
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20231115210212.9981-2-bp@alien8.de
In general users, don't have the necessary information to determine
whether late loading of a new microcode version is safe and does not
modify anything which the currently running kernel uses already, e.g.
removal of CPUID bits or behavioural changes of MSRs.
To address this issue, Intel has added a "minimum required version"
field to a previously reserved field in the microcode header. Microcode
updates should only be applied if the current microcode version is equal
to, or greater than this minimum required version.
Thomas made some suggestions on how meta-data in the microcode file could
provide Linux with information to decide if the new microcode is suitable
candidate for late loading. But even the "simpler" option requires a lot of
metadata and corresponding kernel code to parse it, so the final suggestion
was to add the 'minimum required version' field in the header.
When microcode changes visible features, microcode will set the minimum
required version to its own revision which prevents late loading.
Old microcode blobs have the minimum revision field always set to 0, which
indicates that there is no information and the kernel considers it
unsafe.
This is a pure OS software mechanism. The hardware/firmware ignores this
header field.
For early loading there is no restriction because OS visible features
are enumerated after the early load and therefore a change has no
effect.
The check is always enabled, but by default not enforced. It can be
enforced via Kconfig or kernel command line.
If enforced, the kernel refuses to late load microcode with a minimum
required version field which is zero or when the currently loaded
microcode revision is smaller than the minimum required revision.
If not enforced the load happens independent of the revision check to
stay compatible with the existing behaviour, but it influences the
decision whether the kernel is tainted or not. If the check signals that
the late load is safe, then the kernel is not tainted.
Early loading is not affected by this.
[ tglx: Massaged changelog and fixed up the implementation ]
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20231002115903.776467264@linutronix.de
Applying microcode late can be fatal for the running kernel when the
update changes functionality which is in use already in a non-compatible
way, e.g. by removing a CPUID bit.
There is no way for admins which do not have access to the vendors deep
technical support to decide whether late loading of such a microcode is
safe or not.
Intel has added a new field to the microcode header which tells the
minimal microcode revision which is required to be active in the CPU in
order to be safe.
Provide infrastructure for handling this in the core code and a command
line switch which allows to enforce it.
If the update is considered safe the kernel is not tainted and the annoying
warning message not emitted. If it's enforced and the currently loaded
microcode revision is not safe for late loading then the load is aborted.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20231017211724.079611170@linutronix.de
Offline CPUs need to be parked in a safe loop when microcode update is
in progress on the primary CPU. Currently, offline CPUs are parked in
mwait_play_dead(), and for Intel CPUs, its not a safe instruction,
because the MWAIT instruction can be patched in the new microcode update
that can cause instability.
- Add a new microcode state 'UCODE_OFFLINE' to report status on per-CPU
basis.
- Force NMI on the offline CPUs.
Wake up offline CPUs while the update is in progress and then return
them back to mwait_play_dead() after microcode update is complete.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20231002115903.660850472@linutronix.de
