From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 21 Oct 2021 15:55:09 -0700
Subject: x86/fpu: Add fpu_state_config::legacy_features
Git-commit: c33f0a81a2cf3920465309ce683534751bb86485
Patch-mainline: v5.15 or v5.15-rc8 (next release)
References: jsc#SLE-18931
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
---
arch/x86/include/asm/fpu/types.h | 7 +++++++
arch/x86/kernel/fpu/init.c | 9 ++++++---
2 files changed, 13 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index c3ec56279767..595122fcaf51 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h
@@ -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 */
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 7074154131e6..621f4b6cac4a 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -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;