[PATCH v4 02/21] x86/fpu: Prepare guest FPU for dynamically enabled FPU features
From: Yang Zhong <hidden>
Date: 2021-12-29 13:13:35
Also in:
kvm, linux-kselftest, lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
From: Thomas Gleixner <redacted> To support dynamically enabled FPU features for guests prepare the guest pseudo FPU container to keep track of the currently enabled xfeatures and the guest permissions. Signed-off-by: Thomas Gleixner <redacted> Signed-off-by: Jing Liu <redacted> Signed-off-by: Yang Zhong <redacted> --- arch/x86/include/asm/fpu/types.h | 13 +++++++++++++ arch/x86/kernel/fpu/core.c | 26 +++++++++++++++++++++++++- 2 files changed, 38 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index 6ddf80637697..c752d0aa23a4 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h@@ -504,6 +504,19 @@ struct fpu { * Guest pseudo FPU container */ struct fpu_guest { + /* + * @xfeatures: xfeature bitmap of features which are + * currently enabled for the guest vCPU. + */ + u64 xfeatures; + + /* + * @perm: xfeature bitmap of features which are + * permitted to be enabled for the guest + * vCPU. + */ + u64 perm; + /* * @fpstate: Pointer to the allocated guest fpstate */
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index ab19b3d8b2f7..eddeeb4ed2f5 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c@@ -201,6 +201,26 @@ void fpu_reset_from_exception_fixup(void) #if IS_ENABLED(CONFIG_KVM) static void __fpstate_reset(struct fpstate *fpstate); +static void fpu_init_guest_permissions(struct fpu_guest *gfpu) +{ + struct fpu_state_perm *fpuperm; + u64 perm; + + if (!IS_ENABLED(CONFIG_X86_64)) + return; + + spin_lock_irq(¤t->sighand->siglock); + fpuperm = ¤t->group_leader->thread.fpu.guest_perm; + perm = fpuperm->__state_perm; + + /* First fpstate allocation locks down permissions. */ + WRITE_ONCE(fpuperm->__state_perm, perm | FPU_GUEST_PERM_LOCKED); + + spin_unlock_irq(¤t->sighand->siglock); + + gfpu->perm = perm & ~FPU_GUEST_PERM_LOCKED; +} + bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu) { struct fpstate *fpstate;
@@ -216,7 +236,11 @@ bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu) fpstate->is_valloc = true; fpstate->is_guest = true; - gfpu->fpstate = fpstate; + gfpu->fpstate = fpstate; + gfpu->xfeatures = fpu_user_cfg.default_features; + gfpu->perm = fpu_user_cfg.default_features; + fpu_init_guest_permissions(gfpu); + return true; } EXPORT_SYMBOL_GPL(fpu_alloc_guest_fpstate);