[PATCH v7 05/26] x86/fpu/xstate: Introduce fpu_guest_cfg for guest FPU configuration

[Yang Weijiang <weijiang.yang@xxxxxxxxx>]

Define new fpu_guest_cfg to hold all guest FPU settings so that it can
differ from generic kernel FPU settings, e.g., enabling CET supervisor
xstate by default for guest fpstate while it's remained disabled in
kernel FPU config.

The kernel dynamic xfeatures are specifically used by guest fpstate now,
add the mask for guest fpstate so that guest_perm.__state_permit ==
(fpu_kernel_cfg.default_xfeature | XFEATURE_MASK_KERNEL_DYNAMIC). And
if guest fpstate is re-allocated to hold user dynamic xfeatures, the
resulting permissions are consumed before calculate new guest fpstate.

Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
---
 arch/x86/include/asm/fpu/types.h |  2 +-
 arch/x86/kernel/fpu/core.c       | 14 +++++++++++---
 arch/x86/kernel/fpu/xstate.c     | 10 ++++++++++
 3 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index c6fd13a17205..306825ad6bc0 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h
@@ -602,6 +602,6 @@ struct fpu_state_config {
 };
 
 /* FPU state configuration information */
-extern struct fpu_state_config fpu_kernel_cfg, fpu_user_cfg;
+extern struct fpu_state_config fpu_kernel_cfg, fpu_user_cfg, fpu_guest_cfg;
 
 #endif /* _ASM_X86_FPU_H */
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index a21a4d0ecc34..516af626bf6a 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -33,9 +33,10 @@ DEFINE_STATIC_KEY_FALSE(__fpu_state_size_dynamic);
 DEFINE_PER_CPU(u64, xfd_state);
 #endif
 
-/* The FPU state configuration data for kernel and user space */
+/* The FPU state configuration data for kernel, user space and guest. */
 struct fpu_state_config	fpu_kernel_cfg __ro_after_init;
 struct fpu_state_config fpu_user_cfg __ro_after_init;
+struct fpu_state_config fpu_guest_cfg __ro_after_init;
 
 /*
  * Represents the initial FPU state. It's mostly (but not completely) zeroes,
@@ -536,8 +537,15 @@ 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;
+
+	/* Guest permission settings */
+	fpu->guest_perm.__state_perm	= fpu_guest_cfg.default_features;
+	fpu->guest_perm.__state_size	= fpu_guest_cfg.default_size;
+	/*
+	 * Set guest's __user_state_size to fpu_user_cfg.default_size so that
+	 * existing uAPIs can still work.
+	 */
+	fpu->guest_perm.__user_state_size = fpu_user_cfg.default_size;
 }
 
 static inline void fpu_inherit_perms(struct fpu *dst_fpu)
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index ba4172172afd..aa8f8595cd41 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -681,6 +681,7 @@ static int __init init_xstate_size(void)
 {
 	/* Recompute the context size for enabled features: */
 	unsigned int user_size, kernel_size, kernel_default_size;
+	unsigned int guest_default_size;
 	bool compacted = cpu_feature_enabled(X86_FEATURE_XCOMPACTED);
 
 	/* Uncompacted user space size */
@@ -702,13 +703,18 @@ static int __init init_xstate_size(void)
 	kernel_default_size =
 		xstate_calculate_size(fpu_kernel_cfg.default_features, compacted);
 
+	guest_default_size =
+		xstate_calculate_size(fpu_guest_cfg.default_features, compacted);
+
 	if (!paranoid_xstate_size_valid(kernel_size))
 		return -EINVAL;
 
 	fpu_kernel_cfg.max_size = kernel_size;
 	fpu_user_cfg.max_size = user_size;
+	fpu_guest_cfg.max_size = kernel_size;
 
 	fpu_kernel_cfg.default_size = kernel_default_size;
+	fpu_guest_cfg.default_size = guest_default_size;
 	fpu_user_cfg.default_size =
 		xstate_calculate_size(fpu_user_cfg.default_features, false);
 
@@ -829,6 +835,10 @@ void __init fpu__init_system_xstate(unsigned int legacy_size)
 	fpu_user_cfg.default_features = fpu_user_cfg.max_features;
 	fpu_user_cfg.default_features &= ~XFEATURE_MASK_USER_DYNAMIC;
 
+	fpu_guest_cfg.max_features = fpu_kernel_cfg.max_features;
+	fpu_guest_cfg.default_features = fpu_guest_cfg.max_features;
+	fpu_guest_cfg.default_features &= ~XFEATURE_MASK_USER_DYNAMIC;
+
 	/* Store it for paranoia check at the end */
 	xfeatures = fpu_kernel_cfg.max_features;
 
-- 
2.27.0