Commit c33f0a81 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Borislav Petkov
Browse files

x86/fpu: Add fpu_state_config::legacy_features 



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: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarChang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211021225527.10184-6-chang.seok.bae@intel.com
parent 6f6a7c09

arch/x86/include/asm/fpu/types.h

+7 −0
Original line number Diff line number Diff line
@@ -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 */

arch/x86/kernel/fpu/init.c

+6 −3
Original line number Diff line number Diff line
@@ -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;