3 files changed, 41 insertions, 0 deletions

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 946c06a25d37..ceafe40ec0f9 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -328,6 +328,28 @@ void nested_load_control_from_vmcb12(struct vcpu_svm *svm,
 	svm->nested.ctl.iopm_base_pa  &= ~0x0fffULL;
 }
 
+static void __nested_copy_vmcb_save_to_cache(struct vmcb_save_area_cached *to,
+					     struct vmcb_save_area *from)
+{
+	/*
+	 * Copy only fields that are validated, as we need them
+	 * to avoid TOC/TOU races.
+	 */
+	to->efer = from->efer;
+	to->cr0 = from->cr0;
+	to->cr3 = from->cr3;
+	to->cr4 = from->cr4;
+
+	to->dr6 = from->dr6;
+	to->dr7 = from->dr7;
+}
+
+void nested_copy_vmcb_save_to_cache(struct vcpu_svm *svm,
+				    struct vmcb_save_area *save)
+{
+	__nested_copy_vmcb_save_to_cache(&svm->nested.save, save);
+}
+
 /*
  * Synchronize fields that are written by the processor, so that
  * they can be copied back into the vmcb12.
@@ -670,6 +692,7 @@ int nested_svm_vmrun(struct kvm_vcpu *vcpu)
 		return -EINVAL;
 
 	nested_load_control_from_vmcb12(svm, &vmcb12->control);
+	nested_copy_vmcb_save_to_cache(svm, &vmcb12->save);
 
 	if (!nested_vmcb_valid_sregs(vcpu, &vmcb12->save) ||
 	    !nested_vmcb_check_controls(vcpu, &svm->nested.ctl)) {
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index d0f68d11ec70..20d19162a7f8 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4435,6 +4435,7 @@ static int svm_leave_smm(struct kvm_vcpu *vcpu, const char *smstate)
 
 	vmcb12 = map.hva;
 	nested_load_control_from_vmcb12(svm, &vmcb12->control);
+	nested_copy_vmcb_save_to_cache(svm, &vmcb12->save);
 	ret = enter_svm_guest_mode(vcpu, vmcb12_gpa, vmcb12, false);
 
 unmap_save:
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 1c7306c370fa..4c7365582a5e 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -105,6 +105,15 @@ struct kvm_vmcb_info {
 	uint64_t asid_generation;
 };
 
+struct vmcb_save_area_cached {
+	u64 efer;
+	u64 cr4;
+	u64 cr3;
+	u64 cr0;
+	u64 dr7;
+	u64 dr6;
+};
+
 struct svm_nested_state {
 	struct kvm_vmcb_info vmcb02;
 	u64 hsave_msr;
@@ -122,6 +131,12 @@ struct svm_nested_state {
 	/* cache for control fields of the guest */
 	struct vmcb_control_area ctl;
 
+	/*
+	 * Note: this struct is not kept up-to-date while L2 runs; it is only
+	 * valid within nested_svm_vmrun.
+	 */
+	struct vmcb_save_area_cached save;
+
 	bool initialized;
 };
 
@@ -496,6 +511,8 @@ void nested_svm_update_tsc_ratio_msr(struct kvm_vcpu *vcpu);
 void svm_write_tsc_multiplier(struct kvm_vcpu *vcpu, u64 multiplier);
 void nested_load_control_from_vmcb12(struct vcpu_svm *svm,
 				     struct vmcb_control_area *control);
+void nested_copy_vmcb_save_to_cache(struct vcpu_svm *svm,
+				    struct vmcb_save_area *save);
 void nested_sync_control_from_vmcb02(struct vcpu_svm *svm);
 void nested_vmcb02_compute_g_pat(struct vcpu_svm *svm);
 void svm_switch_vmcb(struct vcpu_svm *svm, struct kvm_vmcb_info *target_vmcb);