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Pull x86 ITS mitigation from Dave Hansen:
"Mitigate Indirect Target Selection (ITS) issue.
I'd describe this one as a good old CPU bug where the behavior is
_obviously_ wrong, but since it just results in bad predictions it
wasn't wrong enough to notice. Well, the researchers noticed and also
realized that thus bug undermined a bunch of existing indirect branch
mitigations.
Thus the unusually wide impact on this one. Details:
ITS is a bug in some Intel CPUs that affects indirect branches
including RETs in the first half of a cacheline. Due to ITS such
branches may get wrongly predicted to a target of (direct or indirect)
branch that is located in the second half of a cacheline. Researchers
at VUSec found this behavior and reported to Intel.
Affected processors:
- Cascade Lake, Cooper Lake, Whiskey Lake V, Coffee Lake R, Comet
Lake, Ice Lake, Tiger Lake and Rocket Lake.
Scope of impact:
- Guest/host isolation:
When eIBRS is used for guest/host isolation, the indirect branches
in the VMM may still be predicted with targets corresponding to
direct branches in the guest.
- Intra-mode using cBPF:
cBPF can be used to poison the branch history to exploit ITS.
Realigning the indirect branches and RETs mitigates this attack
vector.
- User/kernel:
With eIBRS enabled user/kernel isolation is *not* impacted by ITS.
- Indirect Branch Prediction Barrier (IBPB):
Due to this bug indirect branches may be predicted with targets
corresponding to direct branches which were executed prior to IBPB.
This will be fixed in the microcode.
Mitigation:
As indirect branches in the first half of cacheline are affected, the
mitigation is to replace those indirect branches with a call to thunk that
is aligned to the second half of the cacheline.
RETs that take prediction from RSB are not affected, but they may be
affected by RSB-underflow condition. So, RETs in the first half of
cacheline are also patched to a return thunk that executes the RET aligned
to second half of cacheline"
* tag 'its-for-linus-20250509' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
selftest/x86/bugs: Add selftests for ITS
x86/its: FineIBT-paranoid vs ITS
x86/its: Use dynamic thunks for indirect branches
x86/ibt: Keep IBT disabled during alternative patching
mm/execmem: Unify early execmem_cache behaviour
x86/its: Align RETs in BHB clear sequence to avoid thunking
x86/its: Add support for RSB stuffing mitigation
x86/its: Add "vmexit" option to skip mitigation on some CPUs
x86/its: Enable Indirect Target Selection mitigation
x86/its: Add support for ITS-safe return thunk
x86/its: Add support for ITS-safe indirect thunk
x86/its: Enumerate Indirect Target Selection (ITS) bug
Documentation: x86/bugs/its: Add ITS documentation
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Ice Lake generation CPUs are not affected by guest/host isolation part of
ITS. If a user is only concerned about KVM guests, they can now choose a
new cmdline option "vmexit" that will not deploy the ITS mitigation when
CPU is not affected by guest/host isolation. This saves the performance
overhead of ITS mitigation on Ice Lake gen CPUs.
When "vmexit" option selected, if the CPU is affected by ITS guest/host
isolation, the default ITS mitigation is deployed.
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
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ITS bug in some pre-Alderlake Intel CPUs may allow indirect branches in the
first half of a cache line get predicted to a target of a branch located in
the second half of the cache line.
Set X86_BUG_ITS on affected CPUs. Mitigation to follow in later commits.
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
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Classic BPF programs can be run by unprivileged users, allowing
unprivileged code to execute inside the kernel. Attackers can use this to
craft branch history in kernel mode that can influence the target of
indirect branches.
BHI_DIS_S provides user-kernel isolation of branch history, but cBPF can be
used to bypass this protection by crafting branch history in kernel mode.
To stop intra-mode attacks via cBPF programs, Intel created a new
instruction Indirect Branch History Fence (IBHF). IBHF prevents the
predicted targets of subsequent indirect branches from being influenced by
branch history prior to the IBHF. IBHF is only effective while BHI_DIS_S is
enabled.
Add the IBHF instruction to cBPF jitted code's exit path. Add the new fence
when the hardware mitigation is enabled (i.e., X86_FEATURE_CLEAR_BHB_HW is
set) or after the software sequence (X86_FEATURE_CLEAR_BHB_LOOP) is being
used in a virtual machine. Note that X86_FEATURE_CLEAR_BHB_HW and
X86_FEATURE_CLEAR_BHB_LOOP are mutually exclusive, so the JIT compiler will
only emit the new fence, not the SW sequence, when X86_FEATURE_CLEAR_BHB_HW
is set.
Hardware that enumerates BHI_NO basically has BHI_DIS_S protections always
enabled, regardless of the value of BHI_DIS_S. Since BHI_DIS_S doesn't
protect against intra-mode attacks, enumerate BHI bug on BHI_NO hardware as
well.
Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
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Pull x86 speculation mitigation updates from Borislav Petkov:
- Some preparatory work to convert the mitigations machinery to
mitigating attack vectors instead of single vulnerabilities
- Untangle and remove a now unneeded X86_FEATURE_USE_IBPB flag
- Add support for a Zen5-specific SRSO mitigation
- Cleanups and minor improvements
* tag 'x86_bugs_for_v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/bugs: Make spectre user default depend on MITIGATION_SPECTRE_V2
x86/bugs: Use the cpu_smt_possible() helper instead of open-coded code
x86/bugs: Add AUTO mitigations for mds/taa/mmio/rfds
x86/bugs: Relocate mds/taa/mmio/rfds defines
x86/bugs: Add X86_BUG_SPECTRE_V2_USER
x86/bugs: Remove X86_FEATURE_USE_IBPB
KVM: nVMX: Always use IBPB to properly virtualize IBRS
x86/bugs: Use a static branch to guard IBPB on vCPU switch
x86/bugs: Remove the X86_FEATURE_USE_IBPB check in ib_prctl_set()
x86/mm: Remove X86_FEATURE_USE_IBPB checks in cond_mitigation()
x86/bugs: Move the X86_FEATURE_USE_IBPB check into callers
x86/bugs: KVM: Add support for SRSO_MSR_FIX
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Currently, the cpuid_deps[] table is only exercised when a particular
feature is explicitly disabled and clear_cpu_cap() is called. However,
some of these listed dependencies might already be missing during boot.
These types of errors shouldn't generally happen in production
environments, but they could sometimes sneak through, especially when
VMs and Kconfigs are in the mix. Also, the kernel might introduce
artificial dependencies between unrelated features, such as making LAM
depend on LASS.
Unexpected failures can occur when the kernel tries to use such
features. Add a simple boot-time scan of the cpuid_deps[] table to
detect the missing dependencies. One option is to disable all of such
features during boot, but that may cause regressions in existing
systems. For now, just warn about the missing dependencies to create
awareness.
As a trade-off between spamming the kernel log and keeping track of all
the features that have been warned about, only warn about the first
missing dependency. Any subsequent unmet dependency will only be logged
after the first one has been resolved.
Features are typically represented through unsigned integers within the
kernel, though some of them have user-friendly names if they are exposed
via /proc/cpuinfo.
Show the friendlier name if available, otherwise display the
X86_FEATURE_* numerals to make it easier to identify the feature.
Suggested-by: Tony Luck <tony.luck@intel.com>
Suggested-by: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Sohil Mehta <sohil.mehta@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20250313201608.3304135-1-sohil.mehta@intel.com
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The affected CPU table (cpu_vuln_blacklist) marks Alderlake and Raptorlake
P-only parts affected by RFDS. This is not true because only E-cores are
affected by RFDS. With the current family/model matching it is not possible
to differentiate the unaffected parts, as the affected and unaffected
hybrid variants have the same model number.
Add a cpu-type match as well for such parts so as to exclude P-only parts
being marked as affected.
Note, family/model and cpu-type enumeration could be inaccurate in
virtualized environments. In a guest affected status is decided by RFDS_NO
and RFDS_CLEAR bits exposed by VMMs.
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/r/20250311-add-cpu-type-v8-5-e8514dcaaff2@linux.intel.com
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No functional change.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250303165246.2175811-11-brgerst@gmail.com
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No functional change.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250303165246.2175811-10-brgerst@gmail.com
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No functional change.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250303165246.2175811-9-brgerst@gmail.com
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No functional change.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250303165246.2175811-6-brgerst@gmail.com
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No functional change.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250303165246.2175811-4-brgerst@gmail.com
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Also change the alignment of the percpu hot section:
- PERCPU_SECTION(INTERNODE_CACHE_BYTES)
+ PERCPU_SECTION(L1_CACHE_BYTES)
As vSMP will muck with INTERNODE_CACHE_BYTES that invalidates the
too-large-section assert we do:
ASSERT(__per_cpu_hot_end - __per_cpu_hot_start <= 64, "percpu cache hot section too large")
[ mingo: Added INTERNODE_CACHE_BYTES fix & explanation. ]
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250303165246.2175811-3-brgerst@gmail.com
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Signed-off-by: Ingo Molnar <mingo@kernel.org>
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smp_store_cpu_info() is just a wrapper around identify_secondary_cpu()
without further value.
Move the extra bits from smp_store_cpu_info() into identify_secondary_cpu()
and remove the wrapper.
[ darwi: Make it compile and fix up the xen/smp_pv.c instance ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20250304085152.51092-9-darwi@linutronix.de
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Commit:
e0ba94f14f74 ("x86/tlb_info: get last level TLB entry number of CPU")
introduced u16 "info" arrays for each TLB type.
Since 2012 and each array stores just one type of information: the
number of TLB entries for its respective TLB type.
Replace such arrays with simple variables.
Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20250304085152.51092-8-darwi@linutronix.de
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Since using these options is very dangerous, make details as visible as
possible:
- Instead of a single message for each of the cmdline options, print a
separate pr_warn() for each individual flag.
- Say explicitly whether the flag is a "feature" or a "bug".
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20250303-setcpuid-taint-louder-v1-3-8d255032cb4c@google.com
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Commit 814165e9fd1f6 ("x86/cpu: Add the 'setcpuid=' boot parameter")
recently expanded the user's ability to break their system horribly by
overriding effective CPU flags. This was reflected with updates to the
documentation to try and make people aware that this is dangerous.
To further reduce the risk of users mistaking this for a "real feature",
and try to help them figure out why their kernel is tainted if they do
use it:
- Upgrade the existing printk to pr_warn, to help ensure kernel logs
reflect what changes are in effect.
- Print an extra warning that tries to be as dramatic as possible, while
also highlighting the fact that it tainted the kernel.
Suggested-by: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20250303-setcpuid-taint-louder-v1-2-8d255032cb4c@google.com
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These macros used to abstract over CONFIG_X86_FEATURE_NAMES, but that
was removed in:
7583e8fbdc49 ("x86/cpu: Remove X86_FEATURE_NAMES")
Now they are just an unnecessary indirection, remove them.
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20250303-setcpuid-taint-louder-v1-1-8d255032cb4c@google.com
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All CPU vulnerabilities with command line options map to a single X86_BUG bit
except for Spectre V2 where both the spectre_v2 and spectre_v2_user command
line options are related to the same bug.
The spectre_v2 command line options mostly relate to user->kernel and
guest->host mitigations, while the spectre_v2_user command line options relate
to user->user or guest->guest protections.
Define a new X86_BUG bit for spectre_v2_user so each *_select_mitigation()
function in bugs.c is related to a unique X86_BUG bit.
No functional changes.
Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20250108202515.385902-2-david.kaplan@amd.com
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Sometimes it can be very useful to run CPU vulnerability mitigations on
systems where they aren't known to mitigate any real-world
vulnerabilities. This can be handy for mundane reasons like debugging
HW-agnostic logic on whatever machine is to hand, but also for research
reasons: while some mitigations are focused on individual vulns and
uarches, others are fairly general, and it's strategically useful to
have an idea how they'd perform on systems where they aren't currently
needed.
As evidence for this being useful, a flag specifically for Retbleed was
added in:
5c9a92dec323 ("x86/bugs: Add retbleed=force").
Since CPU bugs are tracked using the same basic mechanism as features,
and there are already parameters for manipulating them by hand, extend
that mechanism to support bug as well as capabilities.
With this patch and setcpuid=srso, a QEMU guest running on an Intel host
will boot with Safe-RET enabled.
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20241220-force-cpu-bug-v2-3-7dc71bce742a@google.com
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In preparation for adding support to inject fake CPU bugs at boot-time,
add a general facility to force enablement of CPU flags.
The flag taints the kernel and the documentation attempts to be clear
that this is highly unsuitable for uses outside of kernel development
and platform experimentation.
The new arg is parsed just like clearcpuid, but instead of leading to
setup_clear_cpu_cap() it leads to setup_force_cpu_cap().
I've tested this by booting a nested QEMU guest on an Intel host, which
with setcpuid=svm will claim that it supports AMD virtualization.
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20241220-force-cpu-bug-v2-2-7dc71bce742a@google.com
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This is in preparation for a later commit that will reuse this code, to
make review convenient.
Factor out a helper function which does the full handling for this arg
including printing info to the console.
No functional change intended.
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20241220-force-cpu-bug-v2-1-7dc71bce742a@google.com
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Now that the stack protector canary value is a normal percpu variable,
fixed_percpu_data is unused and can be removed.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250123190747.745588-10-brgerst@gmail.com
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Older versions of GCC fixed the location of the stack protector canary
at %gs:40. This constraint forced the percpu section to be linked at
absolute address 0 so that the canary could be the first data object in
the percpu section. Supporting the zero-based percpu section requires
additional code to handle relocations for RIP-relative references to
percpu data, extra complexity to kallsyms, and workarounds for linker
bugs due to the use of absolute symbols.
GCC 8.1 supports redefining where the canary is located, allowing it to
become a normal percpu variable instead of at a fixed location. This
removes the constraint that the percpu section must be zero-based.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250123190747.745588-8-brgerst@gmail.com
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This CPU was mistakenly given the name INTEL_ATOM_AIRMONT_MID. But it
uses a Silvermont core, not Airmont.
Change #define name to INTEL_ATOM_SILVERMONT_MID2
Reported-by: Christian Ludloff <ludloff@gmail.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20241007165701.19693-1-tony.luck%40intel.com
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Pull x86 cpuid updates from Borislav Petkov:
- Remove the less generic CPU matching infra around struct x86_cpu_desc
and use the generic struct x86_cpu_id thing
- Remove magic naked numbers for CPUID functions and use proper defines
of the prefix CPUID_LEAF_*. Consolidate some of the crazy use around
the tree
- Smaller cleanups and improvements
* tag 'x86_cpu_for_v6.14_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/cpu: Make all all CPUID leaf names consistent
x86/fpu: Remove unnecessary CPUID level check
x86/fpu: Move CPUID leaf definitions to common code
x86/tsc: Remove CPUID "frequency" leaf magic numbers.
x86/tsc: Move away from TSC leaf magic numbers
x86/cpu: Move TSC CPUID leaf definition
x86/cpu: Refresh DCA leaf reading code
x86/cpu: Remove unnecessary MwAIT leaf checks
x86/cpu: Use MWAIT leaf definition
x86/cpu: Move MWAIT leaf definition to common header
x86/cpu: Remove 'x86_cpu_desc' infrastructure
x86/cpu: Move AMD erratum 1386 table over to 'x86_cpu_id'
x86/cpu: Replace PEBS use of 'x86_cpu_desc' use with 'x86_cpu_id'
x86/cpu: Expose only stepping min/max interface
x86/cpu: Introduce new microcode matching helper
x86/cpufeature: Document cpu_feature_enabled() as the default to use
x86/paravirt: Remove the WBINVD callback
x86/cpufeatures: Free up unused feature bits
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If the machine has:
CPUID Fn8000_0021_EAX[30] (SRSO_USER_KERNEL_NO) -- If this bit is 1,
it indicates the CPU is not subject to the SRSO vulnerability across
user/kernel boundaries.
have it fall back to IBPB on VMEXIT only, in the case it is going to run
VMs:
Speculative Return Stack Overflow: Mitigation: IBPB on VMEXIT only
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Link: https://lore.kernel.org/r/20241202120416.6054-2-bp@kernel.org
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The leaf names are not consistent. Give them all a CPUID_LEAF_ prefix
for consistency and vertical alignment.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Dave Jiang <dave.jiang@intel.com> # for ioatdma bits
Link: https://lore.kernel.org/all/20241213205040.7B0C3241%40davehans-spike.ostc.intel.com
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Move the XSAVE-related CPUID leaf definitions to common code. Then,
use the new definition to remove the last magic number from the CPUID
level dependency table.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/all/20241213205037.43C57CDE%40davehans-spike.ostc.intel.com
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The DCA leaf number is also hard-coded in the CPUID level dependency
table. Move its definition to common code and use it.
While at it, fix up the naming and types in the probe code. All
CPUID data is provided in 32-bit registers, not 'unsigned long'.
Also stop referring to "level_9". Move away from test_bit()
because the type is no longer an 'unsigned long'.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/all/20241213205032.476A30FE%40davehans-spike.ostc.intel.com
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The leaf-to-feature dependency array uses hard-coded leaf numbers.
Use the new common header definition for the MWAIT leaf.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/all/20241213205029.5B055D6E%40davehans-spike.ostc.intel.com
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The x86_match_cpu() infrastructure can match CPU steppings. Since
there are only 16 possible steppings, the matching infrastructure goes
all out and stores the stepping match as a bitmap. That means it can
match any possible steppings in a single list entry. Fun.
But it exposes this bitmap to each of the X86_MATCH_*() helpers when
none of them really need a bitmap. It makes up for this by exporting a
helper (X86_STEPPINGS()) which converts a contiguous stepping range
into the bitmap which every single user leverages.
Instead of a bitmap, have the main helper for this sort of thing
(X86_MATCH_VFM_STEPS()) just take a stepping range. This ends up
actually being even more compact than before.
Leave the helper in place (renamed to __X86_STEPPINGS()) to make it
more clear what is going on instead of just having a random GENMASK()
in the middle of an already complicated macro.
One oddity that I hit was this macro:
X86_MATCH_VFM_STEPS(vfm, X86_STEPPING_MIN, max_stepping, issues)
It *could* have been converted over to take a min/max stepping value
for each entry. But that would have been a bit too verbose and would
prevent the one oddball in the list (INTEL_COMETLAKE_L stepping 0)
from sticking out.
Instead, just have it take a *maximum* stepping and imply that the match
is from 0=>max_stepping. This is functional for all the cases now and
also retains the nice property of having INTEL_COMETLAKE_L stepping 0
stick out like a sore thumb.
skx_cpuids[] is goofy. It uses the stepping match but encodes all
possible steppings. Just use a normal, non-stepping match helper.
Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20241213185129.65527B2A%40davehans-spike.ostc.intel.com
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In order to be able to differentiate between AMD and Intel based
systems for very early hypercalls without having to rely on the Xen
hypercall page, make get_cpu_vendor() non-static.
Refactor early_cpu_init() for the same reason by splitting out the
loop initializing cpu_devs() into an externally callable function.
This is part of XSA-466 / CVE-2024-53241.
Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
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Pull x86 fixes from Borislav Petkov:
- Add a terminating zero end-element to the array describing AMD CPUs
affected by erratum 1386 so that the matching loop actually
terminates instead of going off into the weeds
- Update the boot protocol documentation to mention the fact that the
preferred address to load the kernel to is considered in the
relocatable kernel case too
- Flush the memory buffer containing the microcode patch after applying
microcode on AMD Zen1 and Zen2, to avoid unnecessary slowdowns
- Make sure the PPIN CPU feature flag is cleared on all CPUs if PPIN
has been disabled
* tag 'x86_urgent_for_v6.13_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/CPU/AMD: Terminate the erratum_1386_microcode array
x86/Documentation: Update algo in init_size description of boot protocol
x86/microcode/AMD: Flush patch buffer mapping after application
x86/mm: Carve out INVLPG inline asm for use by others
x86/cpu: Fix PPIN initialization
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When the size isn't a small constant, __access_ok() will call
valid_user_address() with the address after the last byte of the user
buffer.
It is valid for a buffer to end with the last valid user address so
valid_user_address() must allow accesses to the base of the guard page.
[ This introduces an off-by-one in the other direction for the plain
non-sized accesses, but since we have that guard region that is a
whole page, those checks "allowing" accesses to that guard region
don't really matter. The access will fault anyway, whether to the
guard page or if the address has been masked to all ones - Linus ]
Fixes: 86e6b1547b3d0 ("x86: fix user address masking non-canonical speculation issue")
Signed-off-by: David Laight <david.laight@aculab.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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On systems that enumerate PPIN (protected processor inventory
number) using CPUID, but where the BIOS locked the MSR to
prevent access /proc/cpuinfo reports "intel_ppin" feature as
present on all logical CPUs except for CPU 0.
This happens because ppin_init() uses x86_match_cpu() to
determine whether PPIN is supported. When called on CPU 0
the test for locked PPIN MSR results in:
clear_cpu_cap(c, info->feature);
This clears the X86 FEATURE bit in boot_cpu_data. When other
CPUs are brought online the x86_match_cpu() fails, and the
PPIN FEATURE bit remains set for those other CPUs.
Fix by using setup_clear_cpu_cap() instead of clear_cpu_cap()
which force clears the FEATURE bit for all CPUS.
Reported-by: Adeel Ashad <adeel.arshad@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20241122234212.27451-1-tony.luck@intel.com
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Pull misc x86 updates from Dave Hansen:
"As usual for this branch, these are super random: a compile fix for
some newish LLVM checks and making sure a Kconfig text reference to
'RSB' matches the normal definition:
- Rework some CPU setup code to keep LLVM happy on 32-bit
- Correct RSB terminology in Kconfig text"
* tag 'x86_misc_for_6.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/cpu: Make sure flag_is_changeable_p() is always being used
x86/bugs: Correct RSB terminology in Kconfig
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Pull x86 splitlock updates from Ingo Molnar:
- Move Split and Bus lock code to a dedicated file (Ravi Bangoria)
- Add split/bus lock support for AMD (Ravi Bangoria)
* tag 'x86-splitlock-2024-11-18' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/bus_lock: Add support for AMD
x86/split_lock: Move Split and Bus lock code to a dedicated file
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Pull x86 cpuid updates from Borislav Petkov:
- Add a feature flag which denotes AMD CPUs supporting workload
classification with the purpose of using such hints when making
scheduling decisions
- Determine the boost enumerator for each AMD core based on its type:
efficiency or performance, in the cppc driver
- Add the type of a CPU to the topology CPU descriptor with the goal of
supporting and making decisions based on the type of the respective
core
- Add a feature flag to denote AMD cores which have heterogeneous
topology and enable SD_ASYM_PACKING for those
- Check microcode revisions before disabling PCID on Intel
- Cleanups and fixlets
* tag 'x86_cpu_for_v6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/cpu: Remove redundant CONFIG_NUMA guard around numa_add_cpu()
x86/cpu: Fix FAM5_QUARK_X1000 to use X86_MATCH_VFM()
x86/cpu: Fix formatting of cpuid_bits[] in scattered.c
x86/cpufeatures: Add X86_FEATURE_AMD_WORKLOAD_CLASS feature bit
x86/amd: Use heterogeneous core topology for identifying boost numerator
x86/cpu: Add CPU type to struct cpuinfo_topology
x86/cpu: Enable SD_ASYM_PACKING for PKG domain on AMD
x86/cpufeatures: Add X86_FEATURE_AMD_HETEROGENEOUS_CORES
x86/cpufeatures: Rename X86_FEATURE_FAST_CPPC to have AMD prefix
x86/mm: Don't disable PCID when INVLPG has been fixed by microcode
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Remove unnecessary CONFIG_NUMA #ifdef around numa_add_cpu() since the
function is already properly handled in <asm/numa.h> for both NUMA and
non-NUMA configurations. For !CONFIG_NUMA builds, numa_add_cpu() is
defined as an empty function.
Simplify the code without any functionality change.
Testing: Build CONFIG_NUMA=n
Signed-off-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20241112072346.428623-1-shivankg@amd.com
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When flag_is_changeable_p() is unused, it prevents kernel builds
with clang, `make W=1` and CONFIG_WERROR=y:
arch/x86/kernel/cpu/common.c:351:19: error: unused function 'flag_is_changeable_p' [-Werror,-Wunused-function]
351 | static inline int flag_is_changeable_p(u32 flag)
| ^~~~~~~~~~~~~~~~~~~~
Fix this by moving core around to make sure flag_is_changeable_p() is
always being used.
See also commit 6863f5643dd7 ("kbuild: allow Clang to find unused static
inline functions for W=1 build").
While at it, fix the argument type to be unsigned long along with
the local variables, although it currently only runs in 32-bit cases.
Besides that, makes it return boolean instead of int. This induces
the change of the returning type of have_cpuid_p() to be boolean
as well.
Suggested-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Link: https://lore.kernel.org/all/20241108153105.1578186-1-andriy.shevchenko%40linux.intel.com
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GCC and Clang both implement stack protector support based on Thread Local
Storage (TLS) variables, and this is used in the kernel to implement per-task
stack cookies, by copying a task's stack cookie into a per-CPU variable every
time it is scheduled in.
Both now also implement -mstack-protector-guard-symbol=, which permits the TLS
variable to be specified directly. This is useful because it will allow to
move away from using a fixed offset of 40 bytes into the per-CPU area on
x86_64, which requires a lot of special handling in the per-CPU code and the
runtime relocation code.
However, while GCC is rather lax in its implementation of this command line
option, Clang actually requires that the provided symbol name refers to a TLS
variable (i.e., one declared with __thread), although it also permits the
variable to be undeclared entirely, in which case it will use an implicit
declaration of the right type.
The upshot of this is that Clang will emit the correct references to the stack
cookie variable in most cases, e.g.,
10d: 64 a1 00 00 00 00 mov %fs:0x0,%eax
10f: R_386_32 __stack_chk_guard
However, if a non-TLS definition of the symbol in question is visible in the
same compilation unit (which amounts to the whole of vmlinux if LTO is
enabled), it will drop the per-CPU prefix and emit a load from a bogus
address.
Work around this by using a symbol name that never occurs in C code, and emit
it as an alias in the linker script.
Fixes: 3fb0fdb3bbe7 ("x86/stackprotector/32: Make the canary into a regular percpu variable")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Cc: stable@vger.kernel.org
Link: https://github.com/ClangBuiltLinux/linux/issues/1854
Link: https://lore.kernel.org/r/20241105155801.1779119-2-brgerst@gmail.com
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It turns out that AMD has a "Meltdown Lite(tm)" issue with non-canonical
accesses in kernel space. And so using just the high bit to decide
whether an access is in user space or kernel space ends up with the good
old "leak speculative data" if you have the right gadget using the
result:
CVE-2020-12965 “Transient Execution of Non-Canonical Accesses“
Now, the kernel surrounds the access with a STAC/CLAC pair, and those
instructions end up serializing execution on older Zen architectures,
which closes the speculation window.
But that was true only up until Zen 5, which renames the AC bit [1].
That improves performance of STAC/CLAC a lot, but also means that the
speculation window is now open.
Note that this affects not just the new address masking, but also the
regular valid_user_address() check used by access_ok(), and the asm
version of the sign bit check in the get_user() helpers.
It does not affect put_user() or clear_user() variants, since there's no
speculative result to be used in a gadget for those operations.
Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Link: https://lore.kernel.org/all/80d94591-1297-4afb-b510-c665efd37f10@citrix.com/
Link: https://lore.kernel.org/all/20241023094448.GAZxjFkEOOF_DM83TQ@fat_crate.local/ [1]
Link: https://www.amd.com/en/resources/product-security/bulletin/amd-sb-1010.html
Link: https://arxiv.org/pdf/2108.10771
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Tested-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com> # LAM case
Fixes: 2865baf54077 ("x86: support user address masking instead of non-speculative conditional")
Fixes: 6014bc27561f ("x86-64: make access_ok() independent of LAM")
Fixes: b19b74bc99b1 ("x86/mm: Rework address range check in get_user() and put_user()")
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Set this flag if the CPU has an IBPB implementation that does not
invalidate return target predictions. Zen generations < 4 do not flush
the RSB when executing an IBPB and this bug flag denotes that.
[ bp: Massage. ]
Signed-off-by: Johannes Wikner <kwikner@ethz.ch>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@kernel.org>
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Pull x86 FRED updates from Thomas Gleixner:
- Enable FRED right after init_mem_mapping() because at that point the
early IDT fault handler is replaced by the real fault handler. The
real fault handler retrieves the faulting address from the stack
frame and not from CR2 when the FRED feature is set. But that
obviously only works when FRED is enabled in the CPU as well.
- Set SS to __KERNEL_DS when enabling FRED to prevent a corner case
where ERETS can observe a SS mismatch and raises a #GP.
* tag 'x86-fred-2024-09-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/entry: Set FRED RSP0 on return to userspace instead of context switch
x86/msr: Switch between WRMSRNS and WRMSR with the alternatives mechanism
x86/entry: Test ti_work for zero before processing individual bits
x86/fred: Set SS to __KERNEL_DS when enabling FRED
x86/fred: Enable FRED right after init_mem_mapping()
x86/fred: Move FRED RSP initialization into a separate function
x86/fred: Parse cmdline param "fred=" in cpu_parse_early_param()
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The Moorefield and Lightning Mountain Atom processors are
missing the NO_SSB flag in the vulnerabilities whitelist.
This will cause unaffected parts to incorrectly be reported
as vulnerable. Add the missing flag.
These parts are currently out of service and were verified
internally with archived documentation that they need the
NO_SSB flag.
Closes: https://lore.kernel.org/lkml/CAEJ9NQdhh+4GxrtG1DuYgqYhvc0hi-sKZh-2niukJ-MyFLntAA@mail.gmail.com/
Reported-by: Shanavas.K.S <shanavasks@gmail.com>
Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240829192437.4074196-1-daniel.sneddon@linux.intel.com
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On 64-bit init_mem_mapping() relies on the minimal page fault handler
provided by the early IDT mechanism. The real page fault handler is
installed right afterwards into the IDT.
This is problematic on CPUs which have X86_FEATURE_FRED set because the
real page fault handler retrieves the faulting address from the FRED
exception stack frame and not from CR2, but that does obviously not work
when FRED is not yet enabled in the CPU.
To prevent this enable FRED right after init_mem_mapping() without
interrupt stacks. Those are enabled later in trap_init() after the CPU
entry area is set up.
[ tglx: Encapsulate the FRED details ]
Fixes: 14619d912b65 ("x86/fred: FRED entry/exit and dispatch code")
Reported-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240709154048.3543361-4-xin@zytor.com
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To enable FRED earlier, move the RSP initialization out of
cpu_init_fred_exceptions() into cpu_init_fred_rsps().
This is required as the FRED RSP initialization depends on the availability
of the CPU entry areas which are set up late in trap_init(),
No functional change intended. Marked with Fixes as it's a depedency for
the real fix.
Fixes: 14619d912b65 ("x86/fred: FRED entry/exit and dispatch code")
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240709154048.3543361-3-xin@zytor.com
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Depending on whether FRED is enabled, sysvec_install() installs a system
interrupt handler into either into FRED's system vector dispatch table or
into the IDT.
However FRED can be disabled later in trap_init(), after sysvec_install()
has been invoked already; e.g., the HYPERVISOR_CALLBACK_VECTOR handler is
registered with sysvec_install() in kvm_guest_init(), which is called in
setup_arch() but way before trap_init().
IOW, there is a gap between FRED is available and available but disabled.
As a result, when FRED is available but disabled, early sysvec_install()
invocations fail to install the IDT handler resulting in spurious
interrupts.
Fix it by parsing cmdline param "fred=" in cpu_parse_early_param() to
ensure that FRED is disabled before the first sysvec_install() incovations.
Fixes: 3810da12710a ("x86/fred: Add a fred= cmdline param")
Reported-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240709154048.3543361-2-xin@zytor.com
|
Linus Torvalds
Pawan Gupta
Daniel Sneddon
Sohil Mehta
Brian Gerst
Ingo Molnar
Thomas Gleixner
Ahmed S. Darwish
Brendan Jackman
David Kaplan
Tony Luck
Borislav Petkov (AMD)
Dave Hansen
Juergen Gross
David Laight
Shivank Garg
Andy Shevchenko
Ard Biesheuvel
Johannes Wikner
Xin Li (Intel)