[PATCH v3 02/10] x86/fpu/xstate: Drop @perm from guest pseudo FPU container

Chao Gao
2025-03-07T16:38:59Z

Remove @perm from the guest pseudo FPU container. The field is
initialized during allocation and never used later.

Rename fpu_init_guest_permissions() to show that its sole purpose is to
lock down guest permissions.

Suggested-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Chao Gao <chao.gao@intel.com>
---
arch/x86/include/asm/fpu/types.h | 7 -------
arch/x86/kernel/fpu/core.c | 7 ++-----
2 files changed, 2 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index 46cc263f9f4f..9f9ed406b179 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h
@@ -526,13 +526,6 @@ struct fpu_guest {
*/
u64 xfeatures;

- /*
- * @perm: xfeature bitmap of features which are
- * permitted to be enabled for the guest
- * vCPU.
- */
- u64 perm;
-
/*
* @xfd_err: Save the guest value.
*/
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 1209c7aebb21..dc169f3d336d 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -195,7 +195,7 @@ void fpu_reset_from_exception_fixup(void)
#if IS_ENABLED(CONFIG_KVM)
static void __fpstate_reset(struct fpstate *fpstate, u64 xfd);

-static void fpu_init_guest_permissions(struct fpu_guest *gfpu)
+static void fpu_lock_guest_permissions(struct fpu_guest *gfpu)
{
struct fpu_state_perm *fpuperm;
u64 perm;
@@ -211,8 +211,6 @@ static void fpu_init_guest_permissions(struct fpu_guest *gfpu)
WRITE_ONCE(fpuperm->__state_perm, perm | FPU_GUEST_PERM_LOCKED);

spin_unlock_irq(&current->sighand->siglock);
-
- gfpu->perm = perm & ~FPU_GUEST_PERM_LOCKED;
}

bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu)
@@ -233,7 +231,6 @@ bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu)

gfpu->fpstate = fpstate;
gfpu->xfeatures = fpu_user_cfg.default_features;
- gfpu->perm = fpu_user_cfg.default_features;

/*
* KVM sets the FP+SSE bits in the XSAVE header when copying FPU state
@@ -248,7 +245,7 @@ bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu)
if (WARN_ON_ONCE(fpu_user_cfg.default_size > gfpu->uabi_size))
gfpu->uabi_size = fpu_user_cfg.default_size;

- fpu_init_guest_permissions(gfpu);
+ fpu_lock_guest_permissions(gfpu);

return true;
}
--
2.46.1