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| author | Chang S. Bae <chang.seok.bae@intel.com> | 2021-10-21 15:55:16 -0700 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2021-10-26 10:18:09 +0200 |
| commit | c351101678ce54492b6e09810ec02efc0df036a9 (patch) | |
| tree | a57a31309b7c38cc2bea01e91b5ed2c297410b3c /arch/x86/include/asm/cpufeatures.h | |
| parent | e61d6310a0f80cb986fd2076d432760b3619fb6d (diff) | |
| download | lwn-c351101678ce54492b6e09810ec02efc0df036a9.tar.gz lwn-c351101678ce54492b6e09810ec02efc0df036a9.zip | |
x86/cpufeatures: Add eXtended Feature Disabling (XFD) feature bit
Intel's eXtended Feature Disable (XFD) feature is an extension of the XSAVE
architecture. XFD allows the kernel to enable a feature state in XCR0 and
to receive a #NM trap when a task uses instructions accessing that state.
This is going to be used to postpone the allocation of a larger XSTATE
buffer for a task to the point where it is actually using a related
instruction after the permission to use that facility has been granted.
XFD is not used by the kernel, but only applied to userspace. This is a
matter of policy as the kernel knows how a fpstate is reallocated and the
XFD state.
The compacted XSAVE format is adjustable for dynamic features. Make XFD
depend on XSAVES.
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211021225527.10184-13-chang.seok.bae@intel.com
Diffstat (limited to 'arch/x86/include/asm/cpufeatures.h')
| -rw-r--r-- | arch/x86/include/asm/cpufeatures.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index d0ce5cfd3ac1..ab7b3a2de85d 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -277,6 +277,7 @@ #define X86_FEATURE_XSAVEC (10*32+ 1) /* XSAVEC instruction */ #define X86_FEATURE_XGETBV1 (10*32+ 2) /* XGETBV with ECX = 1 instruction */ #define X86_FEATURE_XSAVES (10*32+ 3) /* XSAVES/XRSTORS instructions */ +#define X86_FEATURE_XFD (10*32+ 4) /* "" eXtended Feature Disabling */ /* * Extended auxiliary flags: Linux defined - for features scattered in various |