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x86/fpu: Add fpu_state_config::legacy_features

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The upcoming prctl() which is required to request the permission for a
dynamically enabled feature will also provide an option to retrieve the
supported features. If the CPU does not support XSAVE, the supported
features would be 0 even when the CPU supports FP and SSE.

Provide separate storage for the legacy feature set to avoid that and fill
in the bits in the legacy init function.

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/20211021225527.10184-6-chang.seok.bae@intel.com
This commit is contained in:
Thomas Gleixner 2021-10-21 15:55:09 -07:00 committed by Borislav Petkov
parent 6f6a7c09c4
commit c33f0a81a2
2 changed files with 13 additions and 3 deletions
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7
arch/x86/include/asm/fpu/types.h
View File

@ -503,6 +503,13 @@ struct fpu_state_config {
* be requested by user space before usage.
*/
u64 default_features;
/*
* @legacy_features:
*
* Features which can be reported back to user space
* even without XSAVE support, i.e. legacy features FP + SSE
*/
u64 legacy_features;
};
/* FPU state configuration information */

9
arch/x86/kernel/fpu/init.c
View File

@ -193,12 +193,15 @@ static void __init fpu__init_system_xstate_size_legacy(void)
* Note that the size configuration might be overwritten later
* during fpu__init_system_xstate().
*/
if (!cpu_feature_enabled(X86_FEATURE_FPU))
if (!cpu_feature_enabled(X86_FEATURE_FPU)) {
size = sizeof(struct swregs_state);
else if (cpu_feature_enabled(X86_FEATURE_FXSR))
} else if (cpu_feature_enabled(X86_FEATURE_FXSR)) {
size = sizeof(struct fxregs_state);
else
fpu_user_cfg.legacy_features = XFEATURE_MASK_FPSSE;
} else {
size = sizeof(struct fregs_state);
fpu_user_cfg.legacy_features = XFEATURE_MASK_FP;
}
fpu_kernel_cfg.max_size = size;
fpu_kernel_cfg.default_size = size;