[PATCH v4 5/8] x86/fpu: Initialize guest FPU permissions from guest defaults

[Chao Gao]

Currently, fpu->guest_perm is copied from fpu->perm, which is derived from
fpu_kernel_cfg.default_features.

Initialize guest FPU permissions from guest defaults instead of host
defaults. This ensures that any changes to guest_default_{features,size}
are automatically reflected in guest permissions, which in turn guarantees
that fpstate_realloc() allocates a correctly sized XSAVE buffer for guest
FPUs.

Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
---
 arch/x86/kernel/fpu/core.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 0b695c23bbfb..52df97a8a61b 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -542,8 +542,10 @@ 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	= fpu_kernel_cfg.guest_default_features;
+	fpu->guest_perm.__state_size	= fpu_kernel_cfg.guest_default_size;
+	fpu->guest_perm.__user_state_size = fpu_user_cfg.guest_default_size;
 }
 
 static inline void fpu_inherit_perms(struct fpu *dst_fpu)
-- 
2.46.1