2 files changed, 23 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/kvm_book3s_asm.h b/arch/powerpc/include/asm/kvm_book3s_asm.h
index 0bd9348a4db9..412b2f389474 100644
--- a/arch/powerpc/include/asm/kvm_book3s_asm.h
+++ b/arch/powerpc/include/asm/kvm_book3s_asm.h
@@ -106,6 +106,7 @@ struct kvmppc_host_state {
 };
 
 struct kvmppc_book3s_shadow_vcpu {
+        bool in_use;
         ulong gpr[14];
         u32 cr;
         u32 xer;
diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index fe14ca3dd171..5b9e9063cfaf 100644
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -66,6 +66,7 @@ static void kvmppc_core_vcpu_load_pr(struct kvm_vcpu *vcpu, int cpu)
         struct kvmppc_book3s_shadow_vcpu *svcpu = svcpu_get(vcpu);
         memcpy(svcpu->slb, to_book3s(vcpu)->slb_shadow, sizeof(svcpu->slb));
         svcpu->slb_max = to_book3s(vcpu)->slb_shadow_max;
+        svcpu->in_use = 0;
         svcpu_put(svcpu);
 #endif
         vcpu->cpu = smp_processor_id();
@@ -78,6 +79,9 @@ static void kvmppc_core_vcpu_put_pr(struct kvm_vcpu *vcpu)
 {
 #ifdef CONFIG_PPC_BOOK3S_64
         struct kvmppc_book3s_shadow_vcpu *svcpu = svcpu_get(vcpu);
+        if (svcpu->in_use) {
+                kvmppc_copy_from_svcpu(vcpu, svcpu);
+        }
         memcpy(to_book3s(vcpu)->slb_shadow, svcpu->slb, sizeof(svcpu->slb));
         to_book3s(vcpu)->slb_shadow_max = svcpu->slb_max;
         svcpu_put(svcpu);
@@ -110,12 +114,26 @@ void kvmppc_copy_to_svcpu(struct kvmppc_book3s_shadow_vcpu *svcpu,
         svcpu->ctr = vcpu->arch.ctr;
         svcpu->lr  = vcpu->arch.lr;
         svcpu->pc  = vcpu->arch.pc;
+        svcpu->in_use = true;
 }
 
 /* Copy data touched by real-mode code from shadow vcpu back to vcpu */
 void kvmppc_copy_from_svcpu(struct kvm_vcpu *vcpu,
                             struct kvmppc_book3s_shadow_vcpu *svcpu)
 {
+        /*
+         * vcpu_put would just call us again because in_use hasn't
+         * been updated yet.
+         */
+        preempt_disable();
+
+        /*
+         * Maybe we were already preempted and synced the svcpu from
+         * our preempt notifiers. Don't bother touching this svcpu then.
+         */
+        if (!svcpu->in_use)
+                goto out;
+
         vcpu->arch.gpr[0] = svcpu->gpr[0];
         vcpu->arch.gpr[1] = svcpu->gpr[1];
         vcpu->arch.gpr[2] = svcpu->gpr[2];
@@ -139,6 +157,10 @@ void kvmppc_copy_from_svcpu(struct kvm_vcpu *vcpu,
         vcpu->arch.fault_dar   = svcpu->fault_dar;
         vcpu->arch.fault_dsisr = svcpu->fault_dsisr;
         vcpu->arch.last_inst   = svcpu->last_inst;
+        svcpu->in_use = false;
+
+out:
+        preempt_enable();
 }
 
 static int kvmppc_core_check_requests_pr(struct kvm_vcpu *vcpu)