From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 5 Jan 2022 12:35:13 +0000 (-0800)
Subject: x86/fpu: Prepare guest FPU for dynamically enabled FPU features
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=36487e6228c4cb04257c92266a04078a384bc4ec;p=linux.git

x86/fpu: Prepare guest FPU for dynamically enabled FPU features

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 <tglx@linutronix.de>
Signed-off-by: Jing Liu <jing2.liu@intel.com>
Signed-off-by: Yang Zhong <yang.zhong@intel.com>
Message-Id: <20220105123532.12586-3-yang.zhong@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---

diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index 6ddf80637697b..c752d0aa23a46 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 ab19b3d8b2f7b..eddeeb4ed2f52 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(&current->sighand->siglock);
+	fpuperm = &current->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(&current->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);