KVM: PPC: Convert MSR to shared page

One of the most obvious registers to share with the guest directly is the
MSR. The MSR contains the "interrupts enabled" flag which the guest has to
toggle in critical sections.

So in order to bring the overhead of interrupt en- and disabling down, let's
put msr into the shared page. Keep in mind that even though you can fully read
its contents, writing to it doesn't always update all state. There are a few
safe fields that don't require hypervisor interaction. See the documentation
for a list of MSR bits that are safe to be set from inside the guest.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 35 insertions, 30 deletions

diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index b3385dd..2efe692 100644
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c
@@ -115,31 +115,31 @@ static u32 kvmppc_get_dec(struct kvm_vcpu *vcpu)
 
 static void kvmppc_recalc_shadow_msr(struct kvm_vcpu *vcpu)
 {
-	vcpu->arch.shadow_msr = vcpu->arch.msr;
+	ulong smsr = vcpu->arch.shared->msr;
+
 	/* Guest MSR values */
-	vcpu->arch.shadow_msr &= MSR_FE0 | MSR_FE1 | MSR_SF | MSR_SE |
-				 MSR_BE | MSR_DE;
+	smsr &= MSR_FE0 | MSR_FE1 | MSR_SF | MSR_SE | MSR_BE | MSR_DE;
 	/* Process MSR values */
-	vcpu->arch.shadow_msr |= MSR_ME | MSR_RI | MSR_IR | MSR_DR | MSR_PR |
-				 MSR_EE;
+	smsr |= MSR_ME | MSR_RI | MSR_IR | MSR_DR | MSR_PR | MSR_EE;
 	/* External providers the guest reserved */
-	vcpu->arch.shadow_msr |= (vcpu->arch.msr & vcpu->arch.guest_owned_ext);
+	smsr |= (vcpu->arch.shared->msr & vcpu->arch.guest_owned_ext);
 	/* 64-bit Process MSR values */
 #ifdef CONFIG_PPC_BOOK3S_64
-	vcpu->arch.shadow_msr |= MSR_ISF | MSR_HV;
+	smsr |= MSR_ISF | MSR_HV;
 #endif
+	vcpu->arch.shadow_msr = smsr;
 }
 
 void kvmppc_set_msr(struct kvm_vcpu *vcpu, u64 msr)
 {
-	ulong old_msr = vcpu->arch.msr;
+	ulong old_msr = vcpu->arch.shared->msr;
 
 #ifdef EXIT_DEBUG
 	printk(KERN_INFO "KVM: Set MSR to 0x%llx\n", msr);
 #endif
 
 	msr &= to_book3s(vcpu)->msr_mask;
-	vcpu->arch.msr = msr;
+	vcpu->arch.shared->msr = msr;
 	kvmppc_recalc_shadow_msr(vcpu);
 
 	if (msr & (MSR_WE|MSR_POW)) {
@@ -149,21 +149,21 @@ void kvmppc_set_msr(struct kvm_vcpu *vcpu, u64 msr)
 		}
 	}
 
-	if ((vcpu->arch.msr & (MSR_PR|MSR_IR|MSR_DR)) !=
+	if ((vcpu->arch.shared->msr & (MSR_PR|MSR_IR|MSR_DR)) !=
 		   (old_msr & (MSR_PR|MSR_IR|MSR_DR))) {
 		kvmppc_mmu_flush_segments(vcpu);
 		kvmppc_mmu_map_segment(vcpu, kvmppc_get_pc(vcpu));
 	}
 
 	/* Preload FPU if it's enabled */
-	if (vcpu->arch.msr & MSR_FP)
+	if (vcpu->arch.shared->msr & MSR_FP)
 		kvmppc_handle_ext(vcpu, BOOK3S_INTERRUPT_FP_UNAVAIL, MSR_FP);
 }
 
 void kvmppc_inject_interrupt(struct kvm_vcpu *vcpu, int vec, u64 flags)
 {
 	vcpu->arch.srr0 = kvmppc_get_pc(vcpu);
-	vcpu->arch.srr1 = vcpu->arch.msr | flags;
+	vcpu->arch.srr1 = vcpu->arch.shared->msr | flags;
 	kvmppc_set_pc(vcpu, to_book3s(vcpu)->hior + vec);
 	vcpu->arch.mmu.reset_msr(vcpu);
 }
@@ -254,11 +254,11 @@ int kvmppc_book3s_irqprio_deliver(struct kvm_vcpu *vcpu, unsigned int priority)
 
 	switch (priority) {
 	case BOOK3S_IRQPRIO_DECREMENTER:
-		deliver = vcpu->arch.msr & MSR_EE;
+		deliver = vcpu->arch.shared->msr & MSR_EE;
 		vec = BOOK3S_INTERRUPT_DECREMENTER;
 		break;
 	case BOOK3S_IRQPRIO_EXTERNAL:
-		deliver = vcpu->arch.msr & MSR_EE;
+		deliver = vcpu->arch.shared->msr & MSR_EE;
 		vec = BOOK3S_INTERRUPT_EXTERNAL;
 		break;
 	case BOOK3S_IRQPRIO_SYSTEM_RESET:
@@ -437,7 +437,7 @@ static void kvmppc_patch_dcbz(struct kvm_vcpu *vcpu, struct kvmppc_pte *pte)
 static int kvmppc_xlate(struct kvm_vcpu *vcpu, ulong eaddr, bool data,
 			 struct kvmppc_pte *pte)
 {
-	int relocated = (vcpu->arch.msr & (data ? MSR_DR : MSR_IR));
+	int relocated = (vcpu->arch.shared->msr & (data ? MSR_DR : MSR_IR));
 	int r;
 
 	if (relocated) {
@@ -545,8 +545,8 @@ int kvmppc_handle_pagefault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	int page_found = 0;
 	struct kvmppc_pte pte;
 	bool is_mmio = false;
-	bool dr = (vcpu->arch.msr & MSR_DR) ? true : false;
-	bool ir = (vcpu->arch.msr & MSR_IR) ? true : false;
+	bool dr = (vcpu->arch.shared->msr & MSR_DR) ? true : false;
+	bool ir = (vcpu->arch.shared->msr & MSR_IR) ? true : false;
 	u64 vsid;
 
 	relocated = data ? dr : ir;
@@ -563,7 +563,7 @@ int kvmppc_handle_pagefault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 		pte.vpage = eaddr >> 12;
 	}
 
-	switch (vcpu->arch.msr & (MSR_DR|MSR_IR)) {
+	switch (vcpu->arch.shared->msr & (MSR_DR|MSR_IR)) {
 	case 0:
 		pte.vpage |= ((u64)VSID_REAL << (SID_SHIFT - 12));
 		break;
@@ -571,7 +571,7 @@ int kvmppc_handle_pagefault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	case MSR_IR:
 		vcpu->arch.mmu.esid_to_vsid(vcpu, eaddr >> SID_SHIFT, &vsid);
 
-		if ((vcpu->arch.msr & (MSR_DR|MSR_IR)) == MSR_DR)
+		if ((vcpu->arch.shared->msr & (MSR_DR|MSR_IR)) == MSR_DR)
 			pte.vpage |= ((u64)VSID_REAL_DR << (SID_SHIFT - 12));
 		else
 			pte.vpage |= ((u64)VSID_REAL_IR << (SID_SHIFT - 12));
@@ -596,14 +596,16 @@ int kvmppc_handle_pagefault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 		/* Page not found in guest PTE entries */
 		vcpu->arch.dear = kvmppc_get_fault_dar(vcpu);
 		to_book3s(vcpu)->dsisr = to_svcpu(vcpu)->fault_dsisr;
-		vcpu->arch.msr |= (to_svcpu(vcpu)->shadow_srr1 & 0x00000000f8000000ULL);
+		vcpu->arch.shared->msr |=
+			(to_svcpu(vcpu)->shadow_srr1 & 0x00000000f8000000ULL);
 		kvmppc_book3s_queue_irqprio(vcpu, vec);
 	} else if (page_found == -EPERM) {
 		/* Storage protection */
 		vcpu->arch.dear = kvmppc_get_fault_dar(vcpu);
 		to_book3s(vcpu)->dsisr = to_svcpu(vcpu)->fault_dsisr & ~DSISR_NOHPTE;
 		to_book3s(vcpu)->dsisr |= DSISR_PROTFAULT;
-		vcpu->arch.msr |= (to_svcpu(vcpu)->shadow_srr1 & 0x00000000f8000000ULL);
+		vcpu->arch.shared->msr |=
+			(to_svcpu(vcpu)->shadow_srr1 & 0x00000000f8000000ULL);
 		kvmppc_book3s_queue_irqprio(vcpu, vec);
 	} else if (page_found == -EINVAL) {
 		/* Page not found in guest SLB */
@@ -695,9 +697,11 @@ static int kvmppc_read_inst(struct kvm_vcpu *vcpu)
 
 	ret = kvmppc_ld(vcpu, &srr0, sizeof(u32), &last_inst, false);
 	if (ret == -ENOENT) {
-		vcpu->arch.msr = kvmppc_set_field(vcpu->arch.msr, 33, 33, 1);
-		vcpu->arch.msr = kvmppc_set_field(vcpu->arch.msr, 34, 36, 0);
-		vcpu->arch.msr = kvmppc_set_field(vcpu->arch.msr, 42, 47, 0);
+		ulong msr = vcpu->arch.shared->msr;
+
+		msr = kvmppc_set_field(msr, 33, 33, 1);
+		msr = kvmppc_set_field(msr, 34, 36, 0);
+		vcpu->arch.shared->msr = kvmppc_set_field(msr, 42, 47, 0);
 		kvmppc_book3s_queue_irqprio(vcpu, BOOK3S_INTERRUPT_INST_STORAGE);
 		return EMULATE_AGAIN;
 	}
@@ -736,7 +740,7 @@ static int kvmppc_handle_ext(struct kvm_vcpu *vcpu, unsigned int exit_nr,
 	if (vcpu->arch.hflags & BOOK3S_HFLAG_PAIRED_SINGLE)
 		return RESUME_GUEST;
 
-	if (!(vcpu->arch.msr & msr)) {
+	if (!(vcpu->arch.shared->msr & msr)) {
 		kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
 		return RESUME_GUEST;
 	}
@@ -804,7 +808,7 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	if ((exit_nr != 0x900) && (exit_nr != 0x500))
 		printk(KERN_EMERG "exit_nr=0x%x | pc=0x%lx | dar=0x%lx | msr=0x%lx\n",
 			exit_nr, kvmppc_get_pc(vcpu), kvmppc_get_fault_dar(vcpu),
-			vcpu->arch.msr);
+			vcpu->arch.shared->msr);
 #endif
 	kvm_resched(vcpu);
 	switch (exit_nr) {
@@ -836,7 +840,8 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
 			kvmppc_mmu_pte_flush(vcpu, kvmppc_get_pc(vcpu), ~0xFFFUL);
 			r = RESUME_GUEST;
 		} else {
-			vcpu->arch.msr |= to_svcpu(vcpu)->shadow_srr1 & 0x58000000;
+			vcpu->arch.shared->msr |=
+				to_svcpu(vcpu)->shadow_srr1 & 0x58000000;
 			kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
 			kvmppc_mmu_pte_flush(vcpu, kvmppc_get_pc(vcpu), ~0xFFFUL);
 			r = RESUME_GUEST;
@@ -904,7 +909,7 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
 program_interrupt:
 		flags = to_svcpu(vcpu)->shadow_srr1 & 0x1f0000ull;
 
-		if (vcpu->arch.msr & MSR_PR) {
+		if (vcpu->arch.shared->msr & MSR_PR) {
 #ifdef EXIT_DEBUG
 			printk(KERN_INFO "Userspace triggered 0x700 exception at 0x%lx (0x%x)\n", kvmppc_get_pc(vcpu), kvmppc_get_last_inst(vcpu));
 #endif
@@ -1052,7 +1057,7 @@ int kvm_arch_vcpu_ioctl_get_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs)
 	regs->ctr = kvmppc_get_ctr(vcpu);
 	regs->lr = kvmppc_get_lr(vcpu);
 	regs->xer = kvmppc_get_xer(vcpu);
-	regs->msr = vcpu->arch.msr;
+	regs->msr = vcpu->arch.shared->msr;
 	regs->srr0 = vcpu->arch.srr0;
 	regs->srr1 = vcpu->arch.srr1;
 	regs->pid = vcpu->arch.pid;
@@ -1353,7 +1358,7 @@ int __kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
 	local_irq_enable();
 
 	/* Preload FPU if it's enabled */
-	if (vcpu->arch.msr & MSR_FP)
+	if (vcpu->arch.shared->msr & MSR_FP)
 		kvmppc_handle_ext(vcpu, BOOK3S_INTERRUPT_FP_UNAVAIL, MSR_FP);
 
 	ret = __kvmppc_vcpu_entry(kvm_run, vcpu);