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| author | Thomas Gleixner <tglx@linutronix.de> | 2022-04-04 14:11:25 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2022-04-25 15:05:37 +0200 |
| commit | 8ad7e8f696951f192c6629a0cbda9ac94c773159 (patch) | |
| tree | 4031df2db6fbb38b765b6b42a79533ef96c4d85c /arch/x86/include/asm/cpufeatures.h | |
| parent | af2d861d4cd2a4da5137f795ee3509e6f944a25b (diff) | |
| download | linux-8ad7e8f696951f192c6629a0cbda9ac94c773159.tar.gz | |
x86/fpu/xsave: Support XSAVEC in the kernel
XSAVEC is the user space counterpart of XSAVES which cannot save supervisor state. In virtualization scenarios the hypervisor does not expose XSAVES but XSAVEC to the guest, though the kernel does not make use of it. That's unfortunate because XSAVEC uses the compacted format of saving the XSTATE. This is more efficient in terms of storage space vs. XSAVE[OPT] as it does not create holes for XSTATE components which are not supported or enabled by the kernel but are available in hardware. There is room for further optimizations when XSAVEC/S and XGETBV1 are supported. In order to support XSAVEC: - Define the XSAVEC ASM macro as it's not yet supported by the required minimal toolchain. - Create a software defined X86_FEATURE_XCOMPACTED to select the compacted XSTATE buffer format for both XSAVEC and XSAVES. - Make XSAVEC an option in the 'XSAVE' ASM alternatives Requested-by: Andrew Cooper <Andrew.Cooper3@citrix.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20220404104820.598704095@linutronix.de
Diffstat (limited to 'arch/x86/include/asm/cpufeatures.h')
| -rw-r--r-- | arch/x86/include/asm/cpufeatures.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index 73e643ae94b6..ff08da857847 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -201,7 +201,7 @@ #define X86_FEATURE_INVPCID_SINGLE ( 7*32+ 7) /* Effectively INVPCID && CR4.PCIDE=1 */ #define X86_FEATURE_HW_PSTATE ( 7*32+ 8) /* AMD HW-PState */ #define X86_FEATURE_PROC_FEEDBACK ( 7*32+ 9) /* AMD ProcFeedbackInterface */ -/* FREE! ( 7*32+10) */ +#define X86_FEATURE_XCOMPACTED ( 7*32+10) /* "" Use compacted XSTATE (XSAVES or XSAVEC) */ #define X86_FEATURE_PTI ( 7*32+11) /* Kernel Page Table Isolation enabled */ #define X86_FEATURE_RETPOLINE ( 7*32+12) /* "" Generic Retpoline mitigation for Spectre variant 2 */ #define X86_FEATURE_RETPOLINE_LFENCE ( 7*32+13) /* "" Use LFENCE for Spectre variant 2 */ |