The function names for xsave[s]/xrstor[s] operations are horribly named and
a permanent source of confusion.
Rename:
copy_xregs_to_kernel() to os_xsave()
copy_kernel_to_xregs() to os_xrstor()
These are truly low level wrappers around the actual instructions
XSAVE[OPT]/XRSTOR and XSAVES/XRSTORS with the twist that the selection
based on the available CPU features happens with an alternative to avoid
conditionals all over the place and to provide the best performance for hot
paths.
The os_ prefix tells that this is the OS selected mechanism.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121453.830239347@linutronix.de
If the fast path of restoring the FPU state on sigreturn fails or is not
taken and the current task's FPU is active then the FPU has to be
deactivated for the slow path to allow a safe update of the tasks FPU
memory state.
With supervisor states enabled, this requires to save the supervisor state
in the memory state first. Supervisor states require XSAVES so saving only
the supervisor state requires to reshuffle the memory buffer because XSAVES
uses the compacted format and therefore stores the supervisor states at the
beginning of the memory state. That's just an overengineered optimization.
Get rid of it and save the full state for this case.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121453.734561971@linutronix.de
The function does a sanity check with a WARN_ON_ONCE() but happily proceeds
when the pkey argument is out of range.
Clean it up.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121453.635764326@linutronix.de
PKRU is being removed from the kernel XSAVE/FPU buffers. This removal
will probably include warnings for code that look up PKRU in those
buffers.
KVM currently looks up the location of PKRU but doesn't even use the
pointer that it gets back. Rework the code to avoid calling
get_xsave_addr() except in cases where its result is actually used.
This makes the code more clear and also avoids the inevitable PKRU
warnings.
This is probably a good cleanup and could go upstream idependently
of any PKRU rework.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121453.541037562@linutronix.de
This function is pointlessly global and a complete misnomer because it's
usage is related to both supervisor state checks and compacted format
checks. Remove it and just make the conditions check the XSAVES feature.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121453.425493349@linutronix.de
The only usecase for fpu__write_begin is the set() callback of regset, so
the function is pointlessly global.
Move it to the regset code and rename it to fpu_force_restore() which is
exactly decribing what the function does.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121453.328652975@linutronix.de
The function can only be used from the regset get() callbacks safely. So
there is no reason to have it globally exposed.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121453.234942936@linutronix.de
Use the new functionality of copy_xstate_to_uabi_buf() to retrieve the
FX state when XSAVE* is in use. This avoids to overwrite the FPU state
buffer with fpstate_sanitize_xstate() which is error prone and duplicated
code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121453.014441775@linutronix.de
Use the new functionality of copy_xstate_to_uabi_buf() to retrieve the
FX state when XSAVE* is in use. This avoids overwriting the FPU state
buffer with fpstate_sanitize_xstate() which is error prone and duplicated
code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121452.901736860@linutronix.de
When xsave with init state optimization is used then a component's state
in the task's xsave buffer can be stale when the corresponding feature bit
is not set.
fpregs_get() and xfpregs_get() invoke fpstate_sanitize_xstate() to update
the task's xsave buffer before retrieving the FX or FP state. That's just
duplicated code as copy_xstate_to_kernel() already handles this correctly.
Add a copy mode argument to the function which allows to restrict the state
copy to the FP and SSE features.
Also rename the function to copy_xstate_to_uabi_buf() so the name reflects
what it is doing.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121452.805327286@linutronix.de
fpregs_set() has unnecessary complexity to support short or nonzero-offset
writes and to handle the case in which a copy from userspace overwrites
some of the target buffer and then fails. Support for partial writes is
useless -- just require that the write has offset 0 and the correct size,
and copy into a temporary kernel buffer to avoid clobbering the state if
the user access fails.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121452.710467587@linutronix.de
There is no benefit from accepting and silently changing an invalid MXCSR
value supplied via ptrace(). Instead, return -EINVAL on invalid input.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121452.613614842@linutronix.de
xfpregs_set() was incomprehensible. Almost all of the complexity was due
to trying to support nonsensically sized writes or -EFAULT errors that
would have partially or completely overwritten the destination before
failing. Nonsensically sized input would only have been possible using
PTRACE_SETREGSET on REGSET_XFP. Fortunately, it appears (based on Debian
code search results) that no one uses that API at all, let alone with the
wrong sized buffer. Failed user access can be handled more cleanly by
first copying to kernel memory.
Just rewrite it to require sensible input.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121452.504234607@linutronix.de
ptrace() has interfaces that let a ptracer inspect a ptracee's register state.
This includes XSAVE state. The ptrace() ABI includes a hardware-format XSAVE
buffer for both the SETREGS and GETREGS interfaces.
In the old days, the kernel buffer and the ptrace() ABI buffer were the
same boring non-compacted format. But, since the advent of supervisor
states and the compacted format, the kernel buffer has diverged from the
format presented in the ABI.
This leads to two paths in the kernel:
1. Effectively a verbatim copy_to_user() which just copies the kernel buffer
out to userspace. This is used when the kernel buffer is kept in the
non-compacted form which means that it shares a format with the ptrace
ABI.
2. A one-state-at-a-time path: copy_xstate_to_kernel(). This is theoretically
slower since it does a bunch of piecemeal copies.
Remove the verbatim copy case. Speed probably does not matter in this path,
and the vast majority of new hardware will use the one-state-at-a-time path
anyway. This ensures greater testing for the "slow" path.
This also makes enabling PKRU in this interface easier since a single path
can be patched instead of two.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121452.408457100@linutronix.de
Instead of masking out reserved bits, check them and reject the provided
state as invalid if not zero.
Suggested-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121452.308388343@linutronix.de
xstateregs_set() operates on a stopped task and tries to copy the provided
buffer into the task's fpu.state.xsave buffer.
Any error while copying or invalid state detected after copying results in
wiping the target task's FPU state completely including supervisor states.
That's just wrong. The caller supplied invalid data or has a problem with
unmapped memory, so there is absolutely no justification to corrupt the
target state.
Fix this with the following modifications:
1) If data has to be copied from userspace, allocate a buffer and copy from
user first.
2) Use copy_kernel_to_xstate() unconditionally so that header checking
works correctly.
3) Return on error without corrupting the target state.
This prevents corrupting states and lets the caller deal with the problem
it caused in the first place.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121452.214903673@linutronix.de
If the count argument is larger than the xstate size, this will happily
copy beyond the end of xstate.
Fixes: 91c3dba7db ("x86/fpu/xstate: Fix PTRACE frames for XSAVES")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121452.120741557@linutronix.de
They are only used in fpstate_init() and there is no point to have them in
a header just to make reading the code harder.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121452.023118522@linutronix.de
This function is really not doing what the comment advertises:
"Find supported xfeatures based on cpu features and command-line input.
This must be called after fpu__init_parse_early_param() is called and
xfeatures_mask is enumerated."
fpu__init_parse_early_param() does not exist anymore and the function just
returns a constant.
Remove it and fix the caller and get rid of further references to
fpu__init_parse_early_param().
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121451.816404717@linutronix.de
Nothing has to modify this after init.
But of course there is code which unconditionally masks
xfeatures_mask_all on CPU hotplug. This goes unnoticed during boot
hotplug because at that point the variable is still RW mapped.
This is broken in several ways:
1) Masking this in post init CPU hotplug means that any
modification of this state goes unnoticed until actual hotplug
happens.
2) If that ever happens then these bogus feature bits are already
populated all over the place and the system is in inconsistent state
vs. the compacted XSTATE offsets. If at all then this has to panic the
machine because the inconsistency cannot be undone anymore.
Make this a one-time paranoia check in xstate init code and disable
xsave when this happens.
Reported-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121451.712803952@linutronix.de
This cannot work and it's unclear how that ever made a difference.
init_fpstate.xsave.header.xfeatures is always 0 so get_xsave_addr() will
always return a NULL pointer, which will prevent storing the default PKRU
value in init_fpstate.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121451.451391598@linutronix.de
The gap handling in copy_xstate_to_kernel() is wrong when XSAVES is in
use.
Using init_fpstate for copying the init state of features which are
not set in the xstate header is only correct for the legacy area, but
not for the extended features area because when XSAVES is in use then
init_fpstate is in compacted form which means the xstate offsets which
are used to copy from init_fpstate are not valid.
Fortunately, this is not a real problem today because all extended
features in use have an all-zeros init state, but it is wrong
nevertheless and with a potentially dynamically sized init_fpstate this
would result in an access outside of the init_fpstate.
Fix this by keeping track of the last copied state in the target buffer and
explicitly zero it when there is a feature or alignment gap.
Use the compacted offset when accessing the extended feature space in
init_fpstate.
As this is not a functional issue on older kernels this is intentionally
not tagged for stable.
Fixes: b8be15d588 ("x86/fpu/xstate: Re-enable XSAVES")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121451.294282032@linutronix.de
Pick up dependent changes which either went mainline (x86/urgent is
based on -rc7 and that contains them) as urgent fixes and the current
x86/urgent branch which contains two more urgent fixes, so that the
bigger FPU rework can base off ontop.
Signed-off-by: Borislav Petkov <bp@suse.de>
The XSAVE init code initializes all enabled and supported components with
XRSTOR(S) to init state. Then it XSAVEs the state of the components back
into init_fpstate which is used in several places to fill in the init state
of components.
This works correctly with XSAVE, but not with XSAVEOPT and XSAVES because
those use the init optimization and skip writing state of components which
are in init state. So init_fpstate.xsave still contains all zeroes after
this operation.
There are two ways to solve that:
1) Use XSAVE unconditionally, but that requires to reshuffle the buffer when
XSAVES is enabled because XSAVES uses compacted format.
2) Save the components which are known to have a non-zero init state by other
means.
Looking deeper, #2 is the right thing to do because all components the
kernel supports have all-zeroes init state except the legacy features (FP,
SSE). Those cannot be hard coded because the states are not identical on all
CPUs, but they can be saved with FXSAVE which avoids all conditionals.
Use FXSAVE to save the legacy FP/SSE components in init_fpstate along with
a BUILD_BUG_ON() which reminds developers to validate that a newly added
component has all zeroes init state. As a bonus remove the now unused
copy_xregs_to_kernel_booting() crutch.
The XSAVE and reshuffle method can still be implemented in the unlikely
case that components are added which have a non-zero init state and no
other means to save them. For now, FXSAVE is just simple and good enough.
[ bp: Fix a typo or two in the text. ]
Fixes: 6bad06b768 ("x86, xsave: Use xsaveopt in context-switch path when supported")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210618143444.587311343@linutronix.de
sanitize_restored_user_xstate() preserves the supervisor states only
when the fx_only argument is zero, which allows unprivileged user space
to put supervisor states back into init state.
Preserve them unconditionally.
[ bp: Fix a typo or two in the text. ]
Fixes: 5d6b6a6f9b ("x86/fpu/xstate: Update sanitize_restored_xstate() for supervisor xstates")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210618143444.438635017@linutronix.de
(There's a lot more in the pipe):
- Prevent corruption of the XSTATE buffer in signal handling by
validating what is being copied from userspace first.
- Invalidate other task's preserved FPU registers on XRSTOR failure
(#PF) because latter can still modify some of them.
- Restore the proper PKRU value in case userspace modified it
- Reset FPU state when signal restoring fails
Other:
- Map EFI boot services data memory as encrypted in a SEV guest so that
the guest can access it and actually boot properly
- Two SGX correctness fixes: proper resources freeing and a NUMA fix
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Merge tag 'x86_urgent_for_v5.13_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fixes from Borislav Petkov:
"A first set of urgent fixes to the FPU/XSTATE handling mess^W code.
(There's a lot more in the pipe):
- Prevent corruption of the XSTATE buffer in signal handling by
validating what is being copied from userspace first.
- Invalidate other task's preserved FPU registers on XRSTOR failure
(#PF) because latter can still modify some of them.
- Restore the proper PKRU value in case userspace modified it
- Reset FPU state when signal restoring fails
Other:
- Map EFI boot services data memory as encrypted in a SEV guest so
that the guest can access it and actually boot properly
- Two SGX correctness fixes: proper resources freeing and a NUMA fix"
* tag 'x86_urgent_for_v5.13_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/mm: Avoid truncating memblocks for SGX memory
x86/sgx: Add missing xa_destroy() when virtual EPC is destroyed
x86/fpu: Reset state for all signal restore failures
x86/pkru: Write hardware init value to PKRU when xstate is init
x86/process: Check PF_KTHREAD and not current->mm for kernel threads
x86/fpu: Invalidate FPU state after a failed XRSTOR from a user buffer
x86/fpu: Prevent state corruption in __fpu__restore_sig()
x86/ioremap: Map EFI-reserved memory as encrypted for SEV
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Merge tag 'pci-v5.13-fixes-2' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci
Pull PCI fixes from Bjorn Helgaas:
- Clear 64-bit flag for host bridge windows below 4GB to fix a resource
allocation regression added in -rc1 (Punit Agrawal)
- Fix tegra194 MCFG quirk build regressions added in -rc1 (Jon Hunter)
- Avoid secondary bus resets on TI KeyStone C667X devices (Antti
Järvinen)
- Avoid secondary bus resets on some NVIDIA GPUs (Shanker Donthineni)
- Work around FLR erratum on Huawei Intelligent NIC VF (Chiqijun)
- Avoid broken ATS on AMD Navi14 GPU (Evan Quan)
- Trust Broadcom BCM57414 NIC to isolate functions even though it
doesn't advertise ACS support (Sriharsha Basavapatna)
- Work around AMD RS690 BIOSes that don't configure DMA above 4GB
(Mikel Rychliski)
- Fix panic during PIO transfer on Aardvark controller (Pali Rohár)
* tag 'pci-v5.13-fixes-2' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci:
PCI: aardvark: Fix kernel panic during PIO transfer
PCI: Add AMD RS690 quirk to enable 64-bit DMA
PCI: Add ACS quirk for Broadcom BCM57414 NIC
PCI: Mark AMD Navi14 GPU ATS as broken
PCI: Work around Huawei Intelligent NIC VF FLR erratum
PCI: Mark some NVIDIA GPUs to avoid bus reset
PCI: Mark TI C667X to avoid bus reset
PCI: tegra194: Fix MCFG quirk build regressions
PCI: of: Clear 64-bit flag for non-prefetchable memory below 4GB
tl;dr:
Several SGX users reported seeing the following message on NUMA systems:
sgx: [Firmware Bug]: Unable to map EPC section to online node. Fallback to the NUMA node 0.
This turned out to be the memblock code mistakenly throwing away SGX
memory.
=== Full Changelog ===
The 'max_pfn' variable represents the highest known RAM address. It can
be used, for instance, to quickly determine for which physical addresses
there is mem_map[] space allocated. The numa_meminfo code makes an
effort to throw out ("trim") all memory blocks which are above 'max_pfn'.
SGX memory is not considered RAM (it is marked as "Reserved" in the
e820) and is not taken into account by max_pfn. Despite this, SGX memory
areas have NUMA affinity and are enumerated in the ACPI SRAT table. The
existing SGX code uses the numa_meminfo mechanism to look up the NUMA
affinity for its memory areas.
In cases where SGX memory was above max_pfn (usually just the one EPC
section in the last highest NUMA node), the numa_memblock is truncated
at 'max_pfn', which is below the SGX memory. When the SGX code tries to
look up the affinity of this memory, it fails and produces an error message:
sgx: [Firmware Bug]: Unable to map EPC section to online node. Fallback to the NUMA node 0.
and assigns the memory to NUMA node 0.
Instead of silently truncating the memory block at 'max_pfn' and
dropping the SGX memory, add the truncated portion to
'numa_reserved_meminfo'. This allows the SGX code to later determine
the NUMA affinity of its 'Reserved' area.
Before, numa_meminfo looked like this (from 'crash'):
blk = { start = 0x0, end = 0x2080000000, nid = 0x0 }
{ start = 0x2080000000, end = 0x4000000000, nid = 0x1 }
numa_reserved_meminfo is empty.
With this, numa_meminfo looks like this:
blk = { start = 0x0, end = 0x2080000000, nid = 0x0 }
{ start = 0x2080000000, end = 0x4000000000, nid = 0x1 }
and numa_reserved_meminfo has an entry for node 1's SGX memory:
blk = { start = 0x4000000000, end = 0x4080000000, nid = 0x1 }
[ daveh: completely rewrote/reworked changelog ]
Fixes: 5d30f92e76 ("x86/NUMA: Provide a range-to-target_node lookup facility")
Reported-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Fan Du <fan.du@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20210617194657.0A99CB22@viggo.jf.intel.com
Although the AMD RS690 chipset has 64-bit DMA support, BIOS implementations
sometimes fail to configure the memory limit registers correctly.
The Acer F690GVM mainboard uses this chipset and a Marvell 88E8056 NIC. The
sky2 driver programs the NIC to use 64-bit DMA, which will not work:
sky2 0000:02:00.0: error interrupt status=0x8
sky2 0000:02:00.0 eth0: tx timeout
sky2 0000:02:00.0 eth0: transmit ring 0 .. 22 report=0 done=0
Other drivers required by this mainboard either don't support 64-bit DMA,
or have it disabled using driver specific quirks. For example, the ahci
driver has quirks to enable or disable 64-bit DMA depending on the BIOS
version (see ahci_sb600_enable_64bit() in ahci.c). This ahci quirk matches
against the SB600 SATA controller, but the real issue is almost certainly
with the RS690 PCI host that it was commonly attached to.
To avoid this issue in all drivers with 64-bit DMA support, fix the
configuration of the PCI host. If the kernel is aware of physical memory
above 4GB, but the BIOS never configured the PCI host with this
information, update the registers with our values.
[bhelgaas: drop PCI_DEVICE_ID_ATI_RS690 definition]
Link: https://lore.kernel.org/r/20210611214823.4898-1-mikel@mikelr.com
Signed-off-by: Mikel Rychliski <mikel@mikelr.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
reported by syzkaller ("KVM: x86: Immediately reset the MMU context when the SMM
flag is cleared").
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull kvm fixes from Paolo Bonzini:
"Miscellaneous bugfixes.
The main interesting one is a NULL pointer dereference reported by
syzkaller ("KVM: x86: Immediately reset the MMU context when the SMM
flag is cleared")"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
KVM: selftests: Fix kvm_check_cap() assertion
KVM: x86/mmu: Calculate and check "full" mmu_role for nested MMU
KVM: X86: Fix x86_emulator slab cache leak
KVM: SVM: Call SEV Guest Decommission if ASID binding fails
KVM: x86: Immediately reset the MMU context when the SMM flag is cleared
KVM: x86: Fix fall-through warnings for Clang
KVM: SVM: fix doc warnings
KVM: selftests: Fix compiling errors when initializing the static structure
kvm: LAPIC: Restore guard to prevent illegal APIC register access
xa_destroy() needs to be called to destroy a virtual EPC's page array
before calling kfree() to free the virtual EPC. Currently it is not
called so add the missing xa_destroy().
Fixes: 540745ddbc ("x86/sgx: Introduce virtual EPC for use by KVM guests")
Signed-off-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Dave Hansen <dave.hansen@intel.com>
Tested-by: Yang Zhong <yang.zhong@intel.com>
Link: https://lkml.kernel.org/r/20210615101639.291929-1-kai.huang@intel.com
- Fix the NMI watchdog on ancient Intel CPUs
- Remove a misguided, NMI-unsafe KASAN callback
from the NMI-safe irq_work path used by perf.
- Fix uncore events on Ice Lake servers.
- Someone booted maxcpus=1 on an SNB-EP, and the
uncore driver emitted warnings and was probably
buggy. Fix it.
- KCSAN found a genuine data race in the core perf
code. Somewhat ironically the bug was introduced
through a recent race fix. :-/ In our defense, the
new race window was much more narrow. Fix it.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'perf-urgent-2021-06-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf fixes from Ingo Molnar:
"Misc fixes:
- Fix the NMI watchdog on ancient Intel CPUs
- Remove a misguided, NMI-unsafe KASAN callback from the NMI-safe
irq_work path used by perf.
- Fix uncore events on Ice Lake servers.
- Someone booted maxcpus=1 on an SNB-EP, and the uncore driver
emitted warnings and was probably buggy. Fix it.
- KCSAN found a genuine data race in the core perf code. Somewhat
ironically the bug was introduced through a recent race fix. :-/
In our defense, the new race window was much more narrow. Fix it"
* tag 'perf-urgent-2021-06-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/nmi_watchdog: Fix old-style NMI watchdog regression on old Intel CPUs
irq_work: Make irq_work_queue() NMI-safe again
perf/x86/intel/uncore: Fix M2M event umask for Ice Lake server
perf/x86/intel/uncore: Fix a kernel WARNING triggered by maxcpus=1
perf: Fix data race between pin_count increment/decrement
Since LLVM commit 3787ee4, the '-stack-alignment' flag has been dropped
[1], leading to the following error message when building a LTO kernel
with Clang-13 and LLD-13:
ld.lld: error: -plugin-opt=-: ld.lld: Unknown command line argument
'-stack-alignment=8'. Try 'ld.lld --help'
ld.lld: Did you mean '--stackrealign=8'?
It also appears that the '-code-model' flag is not necessary anymore
starting with LLVM-9 [2].
Drop '-code-model' and make '-stack-alignment' conditional on LLD < 13.0.0.
These flags were necessary because these flags were not encoded in the
IR properly, so the link would restart optimizations without them. Now
there are properly encoded in the IR, and these flags exposing
implementation details are no longer necessary.
[1] https://reviews.llvm.org/D103048
[2] https://reviews.llvm.org/D52322
Cc: stable@vger.kernel.org
Link: https://github.com/ClangBuiltLinux/linux/issues/1377
Signed-off-by: Tor Vic <torvic9@mailbox.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/f2c018ee-5999-741e-58d4-e482d5246067@mailbox.org
Calculate and check the full mmu_role when initializing the MMU context
for the nested MMU, where "full" means the bits and pieces of the role
that aren't handled by kvm_calc_mmu_role_common(). While the nested MMU
isn't used for shadow paging, things like the number of levels in the
guest's page tables are surprisingly important when walking the guest
page tables. Failure to reinitialize the nested MMU context if L2's
paging mode changes can result in unexpected and/or missed page faults,
and likely other explosions.
E.g. if an L1 vCPU is running both a 32-bit PAE L2 and a 64-bit L2, the
"common" role calculation will yield the same role for both L2s. If the
64-bit L2 is run after the 32-bit PAE L2, L0 will fail to reinitialize
the nested MMU context, ultimately resulting in a bad walk of L2's page
tables as the MMU will still have a guest root_level of PT32E_ROOT_LEVEL.
WARNING: CPU: 4 PID: 167334 at arch/x86/kvm/vmx/vmx.c:3075 ept_save_pdptrs+0x15/0xe0 [kvm_intel]
Modules linked in: kvm_intel]
CPU: 4 PID: 167334 Comm: CPU 3/KVM Not tainted 5.13.0-rc1-d849817d5673-reqs #185
Hardware name: ASUS Q87M-E/Q87M-E, BIOS 1102 03/03/2014
RIP: 0010:ept_save_pdptrs+0x15/0xe0 [kvm_intel]
Code: <0f> 0b c3 f6 87 d8 02 00f
RSP: 0018:ffffbba702dbba00 EFLAGS: 00010202
RAX: 0000000000000011 RBX: 0000000000000002 RCX: ffffffff810a2c08
RDX: ffff91d7bc30acc0 RSI: 0000000000000011 RDI: ffff91d7bc30a600
RBP: ffff91d7bc30a600 R08: 0000000000000010 R09: 0000000000000007
R10: 0000000000000000 R11: 0000000000000000 R12: ffff91d7bc30a600
R13: ffff91d7bc30acc0 R14: ffff91d67c123460 R15: 0000000115d7e005
FS: 00007fe8e9ffb700(0000) GS:ffff91d90fb00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000029f15a001 CR4: 00000000001726e0
Call Trace:
kvm_pdptr_read+0x3a/0x40 [kvm]
paging64_walk_addr_generic+0x327/0x6a0 [kvm]
paging64_gva_to_gpa_nested+0x3f/0xb0 [kvm]
kvm_fetch_guest_virt+0x4c/0xb0 [kvm]
__do_insn_fetch_bytes+0x11a/0x1f0 [kvm]
x86_decode_insn+0x787/0x1490 [kvm]
x86_decode_emulated_instruction+0x58/0x1e0 [kvm]
x86_emulate_instruction+0x122/0x4f0 [kvm]
vmx_handle_exit+0x120/0x660 [kvm_intel]
kvm_arch_vcpu_ioctl_run+0xe25/0x1cb0 [kvm]
kvm_vcpu_ioctl+0x211/0x5a0 [kvm]
__x64_sys_ioctl+0x83/0xb0
do_syscall_64+0x40/0xb0
entry_SYSCALL_64_after_hwframe+0x44/0xae
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: stable@vger.kernel.org
Fixes: bf627a9288 ("x86/kvm/mmu: check if MMU reconfiguration is needed in init_kvm_nested_mmu()")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210610220026.1364486-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Commit c9b8b07cde (KVM: x86: Dynamically allocate per-vCPU emulation context)
tries to allocate per-vCPU emulation context dynamically, however, the
x86_emulator slab cache is still exiting after the kvm module is unload
as below after destroying the VM and unloading the kvm module.
grep x86_emulator /proc/slabinfo
x86_emulator 36 36 2672 12 8 : tunables 0 0 0 : slabdata 3 3 0
This patch fixes this slab cache leak by destroying the x86_emulator slab cache
when the kvm module is unloaded.
Fixes: c9b8b07cde (KVM: x86: Dynamically allocate per-vCPU emulation context)
Cc: stable@vger.kernel.org
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Message-Id: <1623387573-5969-1-git-send-email-wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Send SEV_CMD_DECOMMISSION command to PSP firmware if ASID binding
fails. If a failure happens after a successful LAUNCH_START command,
a decommission command should be executed. Otherwise, guest context
will be unfreed inside the AMD SP. After the firmware will not have
memory to allocate more SEV guest context, LAUNCH_START command will
begin to fail with SEV_RET_RESOURCE_LIMIT error.
The existing code calls decommission inside sev_unbind_asid, but it is
not called if a failure happens before guest activation succeeds. If
sev_bind_asid fails, decommission is never called. PSP firmware has a
limit for the number of guests. If sev_asid_binding fails many times,
PSP firmware will not have resources to create another guest context.
Cc: stable@vger.kernel.org
Fixes: 59414c9892 ("KVM: SVM: Add support for KVM_SEV_LAUNCH_START command")
Reported-by: Peter Gonda <pgonda@google.com>
Signed-off-by: Alper Gun <alpergun@google.com>
Reviewed-by: Marc Orr <marcorr@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210610174604.2554090-1-alpergun@google.com>
Immediately reset the MMU context when the vCPU's SMM flag is cleared so
that the SMM flag in the MMU role is always synchronized with the vCPU's
flag. If RSM fails (which isn't correctly emulated), KVM will bail
without calling post_leave_smm() and leave the MMU in a bad state.
The bad MMU role can lead to a NULL pointer dereference when grabbing a
shadow page's rmap for a page fault as the initial lookups for the gfn
will happen with the vCPU's SMM flag (=0), whereas the rmap lookup will
use the shadow page's SMM flag, which comes from the MMU (=1). SMM has
an entirely different set of memslots, and so the initial lookup can find
a memslot (SMM=0) and then explode on the rmap memslot lookup (SMM=1).
general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 1 PID: 8410 Comm: syz-executor382 Not tainted 5.13.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__gfn_to_rmap arch/x86/kvm/mmu/mmu.c:935 [inline]
RIP: 0010:gfn_to_rmap+0x2b0/0x4d0 arch/x86/kvm/mmu/mmu.c:947
Code: <42> 80 3c 20 00 74 08 4c 89 ff e8 f1 79 a9 00 4c 89 fb 4d 8b 37 44
RSP: 0018:ffffc90000ffef98 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff888015b9f414 RCX: ffff888019669c40
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001
RBP: 0000000000000001 R08: ffffffff811d9cdb R09: ffffed10065a6002
R10: ffffed10065a6002 R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000003 R14: 0000000000000001 R15: 0000000000000000
FS: 000000000124b300(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000028e31000 CR4: 00000000001526e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
rmap_add arch/x86/kvm/mmu/mmu.c:965 [inline]
mmu_set_spte+0x862/0xe60 arch/x86/kvm/mmu/mmu.c:2604
__direct_map arch/x86/kvm/mmu/mmu.c:2862 [inline]
direct_page_fault+0x1f74/0x2b70 arch/x86/kvm/mmu/mmu.c:3769
kvm_mmu_do_page_fault arch/x86/kvm/mmu.h:124 [inline]
kvm_mmu_page_fault+0x199/0x1440 arch/x86/kvm/mmu/mmu.c:5065
vmx_handle_exit+0x26/0x160 arch/x86/kvm/vmx/vmx.c:6122
vcpu_enter_guest+0x3bdd/0x9630 arch/x86/kvm/x86.c:9428
vcpu_run+0x416/0xc20 arch/x86/kvm/x86.c:9494
kvm_arch_vcpu_ioctl_run+0x4e8/0xa40 arch/x86/kvm/x86.c:9722
kvm_vcpu_ioctl+0x70f/0xbb0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3460
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:1069 [inline]
__se_sys_ioctl+0xfb/0x170 fs/ioctl.c:1055
do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x440ce9
Cc: stable@vger.kernel.org
Reported-by: syzbot+fb0b6a7e8713aeb0319c@syzkaller.appspotmail.com
Fixes: 9ec19493fb ("KVM: x86: clear SMM flags before loading state while leaving SMM")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210609185619.992058-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In preparation to enable -Wimplicit-fallthrough for Clang, fix a couple
of warnings by explicitly adding break statements instead of just letting
the code fall through to the next case.
Link: https://github.com/KSPP/linux/issues/115
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Message-Id: <20210528200756.GA39320@embeddedor>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Fix kernel-doc warnings:
arch/x86/kvm/svm/avic.c:233: warning: Function parameter or member 'activate' not described in 'avic_update_access_page'
arch/x86/kvm/svm/avic.c:233: warning: Function parameter or member 'kvm' not described in 'avic_update_access_page'
arch/x86/kvm/svm/avic.c:781: warning: Function parameter or member 'e' not described in 'get_pi_vcpu_info'
arch/x86/kvm/svm/avic.c:781: warning: Function parameter or member 'kvm' not described in 'get_pi_vcpu_info'
arch/x86/kvm/svm/avic.c:781: warning: Function parameter or member 'svm' not described in 'get_pi_vcpu_info'
arch/x86/kvm/svm/avic.c:781: warning: Function parameter or member 'vcpu_info' not described in 'get_pi_vcpu_info'
arch/x86/kvm/svm/avic.c:1009: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
Signed-off-by: ChenXiaoSong <chenxiaosong2@huawei.com>
Message-Id: <20210609122217.2967131-1-chenxiaosong2@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The following commit:
3a4ac121c2 ("x86/perf: Add hardware performance events support for Zhaoxin CPU.")
Got the old-style NMI watchdog logic wrong and broke it for basically every
Intel CPU where it was active. Which is only truly old CPUs, so few people noticed.
On CPUs with perf events support we turn off the old-style NMI watchdog, so it
was pretty pointless to add the logic for X86_VENDOR_ZHAOXIN to begin with ... :-/
Anyway, the fix is to restore the old logic and add a 'break'.
[ mingo: Wrote a new changelog. ]
Fixes: 3a4ac121c2 ("x86/perf: Add hardware performance events support for Zhaoxin CPU.")
Signed-off-by: CodyYao-oc <CodyYao-oc@zhaoxin.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210607025335.9643-1-CodyYao-oc@zhaoxin.com
If access_ok() or fpregs_soft_set() fails in __fpu__restore_sig() then the
function just returns but does not clear the FPU state as it does for all
other fatal failures.
Clear the FPU state for these failures as well.
Fixes: 72a671ced6 ("x86, fpu: Unify signal handling code paths for x86 and x86_64 kernels")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/87mtryyhhz.ffs@nanos.tec.linutronix.de
Per the SDM, "any access that touches bytes 4 through 15 of an APIC
register may cause undefined behavior and must not be executed."
Worse, such an access in kvm_lapic_reg_read can result in a leak of
kernel stack contents. Prior to commit 01402cf810 ("kvm: LAPIC:
write down valid APIC registers"), such an access was explicitly
disallowed. Restore the guard that was removed in that commit.
Fixes: 01402cf810 ("kvm: LAPIC: write down valid APIC registers")
Signed-off-by: Jim Mattson <jmattson@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Message-Id: <20210602205224.3189316-1-jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
without nested page tables.
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull kvm fixes from Paolo Bonzini:
"Bugfixes, including a TLB flush fix that affects processors without
nested page tables"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
kvm: fix previous commit for 32-bit builds
kvm: avoid speculation-based attacks from out-of-range memslot accesses
KVM: x86: Unload MMU on guest TLB flush if TDP disabled to force MMU sync
KVM: x86: Ensure liveliness of nested VM-Enter fail tracepoint message
selftests: kvm: Add support for customized slot0 memory size
KVM: selftests: introduce P47V64 for s390x
KVM: x86: Ensure PV TLB flush tracepoint reflects KVM behavior
KVM: X86: MMU: Use the correct inherited permissions to get shadow page
KVM: LAPIC: Write 0 to TMICT should also cancel vmx-preemption timer
KVM: SVM: Fix SEV SEND_START session length & SEND_UPDATE_DATA query length after commit 238eca821c
copy_user_to_xstate() uses __copy_from_user(), which provides a negligible
speedup. Fortunately, both call sites are at least almost correct.
__fpu__restore_sig() checks access_ok() with xstate_sigframe_size()
length and ptrace regset access uses fpu_user_xstate_size. These should
be valid upper bounds on the length, so, at worst, this would cause
spurious failures and not accesses to kernel memory.
Nonetheless, this is far more fragile than necessary and none of these
callers are in a hotpath.
Use copy_from_user() instead.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Rik van Riel <riel@surriel.com>
Link: https://lkml.kernel.org/r/20210608144346.140254130@linutronix.de
When user space brings PKRU into init state, then the kernel handling is
broken:
T1 user space
xsave(state)
state.header.xfeatures &= ~XFEATURE_MASK_PKRU;
xrstor(state)
T1 -> kernel
schedule()
XSAVE(S) -> T1->xsave.header.xfeatures[PKRU] == 0
T1->flags |= TIF_NEED_FPU_LOAD;
wrpkru();
schedule()
...
pk = get_xsave_addr(&T1->fpu->state.xsave, XFEATURE_PKRU);
if (pk)
wrpkru(pk->pkru);
else
wrpkru(DEFAULT_PKRU);
Because the xfeatures bit is 0 and therefore the value in the xsave
storage is not valid, get_xsave_addr() returns NULL and switch_to()
writes the default PKRU. -> FAIL #1!
So that wrecks any copy_to/from_user() on the way back to user space
which hits memory which is protected by the default PKRU value.
Assumed that this does not fail (pure luck) then T1 goes back to user
space and because TIF_NEED_FPU_LOAD is set it ends up in
switch_fpu_return()
__fpregs_load_activate()
if (!fpregs_state_valid()) {
load_XSTATE_from_task();
}
But if nothing touched the FPU between T1 scheduling out and back in,
then the fpregs_state is still valid which means switch_fpu_return()
does nothing and just clears TIF_NEED_FPU_LOAD. Back to user space with
DEFAULT_PKRU loaded. -> FAIL #2!
The fix is simple: if get_xsave_addr() returns NULL then set the
PKRU value to 0 instead of the restrictive default PKRU value in
init_pkru_value.
[ bp: Massage in minor nitpicks from folks. ]
Fixes: 0cecca9d03 ("x86/fpu: Eager switch PKRU state")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Rik van Riel <riel@surriel.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210608144346.045616965@linutronix.de
switch_fpu_finish() checks current->mm as indicator for kernel threads.
That's wrong because kernel threads can temporarily use a mm of a user
process via kthread_use_mm().
Check the task flags for PF_KTHREAD instead.
Fixes: 0cecca9d03 ("x86/fpu: Eager switch PKRU state")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Rik van Riel <riel@surriel.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210608144345.912645927@linutronix.de
Both Intel and AMD consider it to be architecturally valid for XRSTOR to
fail with #PF but nonetheless change the register state. The actual
conditions under which this might occur are unclear [1], but it seems
plausible that this might be triggered if one sibling thread unmaps a page
and invalidates the shared TLB while another sibling thread is executing
XRSTOR on the page in question.
__fpu__restore_sig() can execute XRSTOR while the hardware registers
are preserved on behalf of a different victim task (using the
fpu_fpregs_owner_ctx mechanism), and, in theory, XRSTOR could fail but
modify the registers.
If this happens, then there is a window in which __fpu__restore_sig()
could schedule out and the victim task could schedule back in without
reloading its own FPU registers. This would result in part of the FPU
state that __fpu__restore_sig() was attempting to load leaking into the
victim task's user-visible state.
Invalidate preserved FPU registers on XRSTOR failure to prevent this
situation from corrupting any state.
[1] Frequent readers of the errata lists might imagine "complex
microarchitectural conditions".
Fixes: 1d731e731c ("x86/fpu: Add a fastpath to __fpu__restore_sig()")
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Rik van Riel <riel@surriel.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210608144345.758116583@linutronix.de
