From: Chao Gao Date: Thu, 22 May 2025 15:10:05 +0000 (-0700) Subject: x86/fpu: Initialize guest FPU permissions from guest defaults X-Git-Tag: v6.17-rc1~136^2~5 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7c2c89364d9219f3a31a9a930476de5c154f13bd;p=thirdparty%2Flinux.git x86/fpu: Initialize guest FPU permissions from guest defaults Currently, fpu->guest_perm is copied from fpu->perm, which is derived from fpu_kernel_cfg.default_features. Guest defaults were introduced to differentiate the features and sizes of host and guest FPUs. Copying guest FPU permissions from the host will lead to inconsistencies between the guest default features and permissions. Initialize guest FPU permissions from guest defaults instead of host defaults. This ensures that any changes to guest default features are automatically reflected in guest permissions, which in turn guarantees that fpstate_realloc() allocates a correctly sized XSAVE buffer for guest FPUs. Suggested-by: Chang S. Bae Signed-off-by: Chao Gao Signed-off-by: Dave Hansen Reviewed-by: Rick Edgecombe Reviewed-by: John Allen Link: https://lore.kernel.org/all/20250522151031.426788-3-chao.gao%40intel.com --- diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index aa7252323cddf..94706a596aaa9 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -562,8 +562,14 @@ void fpstate_reset(struct fpu *fpu) fpu->perm.__state_perm = fpu_kernel_cfg.default_features; fpu->perm.__state_size = fpu_kernel_cfg.default_size; fpu->perm.__user_state_size = fpu_user_cfg.default_size; - /* Same defaults for guests */ - fpu->guest_perm = fpu->perm; + + fpu->guest_perm.__state_perm = guest_default_cfg.features; + fpu->guest_perm.__state_size = guest_default_cfg.size; + /* + * User features and sizes are always identical between host and + * guest FPUs, which allows for common guest and userspace ABI. + */ + fpu->guest_perm.__user_state_size = fpu_user_cfg.default_size; } static inline void fpu_inherit_perms(struct fpu *dst_fpu)