KVM: PPC: booke: save/restore VRSAVE (a.k.a. USPRG0)

Linux doesn't use USPRG0 (now renamed VRSAVE in the architecture, even
when Altivec isn't involved), but a guest might.
Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

arch/powerpc/include/asm/kvm_host.h

@@ -223,6 +223,7 @@ struct kvm_vcpu_arch {
 	ulong hflags;
 	ulong guest_owned_ext;
 #endif
+	u32 vrsave; /* also USPRG0 */
 	u32 mmucr;
 	ulong sprg4;
 	ulong sprg5;

arch/powerpc/kernel/asm-offsets.c

@@ -395,6 +395,7 @@ int main(void)
 	DEFINE(VCPU_HOST_STACK, offsetof(struct kvm_vcpu, arch.host_stack));
 	DEFINE(VCPU_HOST_PID, offsetof(struct kvm_vcpu, arch.host_pid));
 	DEFINE(VCPU_GPRS, offsetof(struct kvm_vcpu, arch.gpr));
+	DEFINE(VCPU_VRSAVE, offsetof(struct kvm_vcpu, arch.vrsave));
 	DEFINE(VCPU_SPRG4, offsetof(struct kvm_vcpu, arch.sprg4));
 	DEFINE(VCPU_SPRG5, offsetof(struct kvm_vcpu, arch.sprg5));
 	DEFINE(VCPU_SPRG6, offsetof(struct kvm_vcpu, arch.sprg6));

arch/powerpc/kvm/booke_interrupts.S

@@ -380,7 +380,6 @@ lightweight_exit:
 	 * because host interrupt handlers would get confused. */
 	lwz	r1, VCPU_GPR(r1)(r4)
 
-	/* XXX handle USPRG0 */
 	/* Host interrupt handlers may have clobbered these guest-readable
 	 * SPRGs, so we need to reload them here with the guest's values. */
 	lwz	r3, VCPU_SPRG4(r4)

arch/powerpc/kvm/powerpc.c

@@ -298,12 +298,25 @@ void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu)
 
 void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 {
+#ifdef CONFIG_BOOKE
+	/*
+	 * vrsave (formerly usprg0) isn't used by Linux, but may
+	 * be used by the guest.
+	 *
+	 * On non-booke this is associated with Altivec and
+	 * is handled by code in book3s.c.
+	 */
+	mtspr(SPRN_VRSAVE, vcpu->arch.vrsave);
+#endif
 	kvmppc_core_vcpu_load(vcpu, cpu);
 }
 
 void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 {
 	kvmppc_core_vcpu_put(vcpu);
+#ifdef CONFIG_BOOKE
+	vcpu->arch.vrsave = mfspr(SPRN_VRSAVE);
+#endif
 }
 
 int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,