[PATCH RFC 4/7] x86/kvm/mmu: introduce guest_mmu

[Vitaly Kuznetsov]

When EPT is used for nested guest we need to re-init MMU as shadow
EPT MMU (nested_ept_init_mmu_context() does that). When we return back
from L2 to L1 kvm_mmu_reset_context() in nested_vmx_load_cr3() resets
MMU back to normal TDP mode. Add a special 'guest_mmu' so we can avoid
structure re-initialization and MMU root reload (in future, this is a
preparatory patch).

Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
 arch/x86/include/asm/kvm_host.h |  3 +++
 arch/x86/kvm/mmu.c              | 12 ++++++++----
 arch/x86/kvm/vmx.c              | 29 ++++++++++++++++++++---------
 3 files changed, 31 insertions(+), 13 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d819947d0a97..3d0d26142619 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -526,6 +526,9 @@ struct kvm_vcpu_arch {
 	/* Non-nested MMU for L1 */
 	struct kvm_mmu root_mmu;
 
+	/* L1 MMU when running nested */
+	struct kvm_mmu guest_mmu;
+
 	/*
 	 * Paging state of an L2 guest (used for nested npt)
 	 *
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 8c5e5664d830..76849eda1a5b 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4670,8 +4670,10 @@ EXPORT_SYMBOL_GPL(kvm_mmu_load);
 
 void kvm_mmu_unload(struct kvm_vcpu *vcpu)
 {
-	kvm_mmu_free_roots(vcpu, vcpu->arch.mmu);
-	WARN_ON(VALID_PAGE(vcpu->arch.mmu->root_hpa));
+	kvm_mmu_free_roots(vcpu, &vcpu->arch.root_mmu);
+	WARN_ON(VALID_PAGE(vcpu->arch.root_mmu.root_hpa));
+	kvm_mmu_free_roots(vcpu, &vcpu->arch.guest_mmu);
+	WARN_ON(VALID_PAGE(vcpu->arch.guest_mmu.root_hpa));
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_unload);
 
@@ -5051,8 +5053,10 @@ int kvm_mmu_create(struct kvm_vcpu *vcpu)
 {
 	vcpu->arch.mmu = &vcpu->arch.root_mmu;
 	vcpu->arch.walk_mmu = &vcpu->arch.root_mmu;
-	vcpu->arch.mmu->root_hpa = INVALID_PAGE;
-	vcpu->arch.mmu->translate_gpa = translate_gpa;
+	vcpu->arch.root_mmu.root_hpa = INVALID_PAGE;
+	vcpu->arch.root_mmu.translate_gpa = translate_gpa;
+	vcpu->arch.guest_mmu.root_hpa = INVALID_PAGE;
+	vcpu->arch.guest_mmu.translate_gpa = translate_gpa;
 	vcpu->arch.nested_mmu.translate_gpa = translate_nested_gpa;
 
 	return alloc_mmu_pages(vcpu);
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 418277fd1b7c..5feb52991065 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8012,8 +8012,10 @@ static inline void nested_release_vmcs12(struct vcpu_vmx *vmx)
  * Free whatever needs to be freed from vmx->nested when L1 goes down, or
  * just stops using VMX.
  */
-static void free_nested(struct vcpu_vmx *vmx)
+static void free_nested(struct kvm_vcpu *vcpu)
 {
+	struct vcpu_vmx *vmx = to_vmx(vcpu);
+
 	if (!vmx->nested.vmxon && !vmx->nested.smm.vmxon)
 		return;
 
@@ -8045,6 +8047,8 @@ static void free_nested(struct vcpu_vmx *vmx)
 		vmx->nested.pi_desc = NULL;
 	}
 
+	kvm_mmu_free_roots(vcpu, &vcpu->arch.guest_mmu);
+
 	free_loaded_vmcs(&vmx->nested.vmcs02);
 }
 
@@ -8053,7 +8057,7 @@ static int handle_vmoff(struct kvm_vcpu *vcpu)
 {
 	if (!nested_vmx_check_permission(vcpu))
 		return 1;
-	free_nested(to_vmx(vcpu));
+	free_nested(vcpu);
 	nested_vmx_succeed(vcpu);
 	return kvm_skip_emulated_instruction(vcpu);
 }
@@ -8084,6 +8088,8 @@ static int handle_vmclear(struct kvm_vcpu *vcpu)
 	if (vmptr == vmx->nested.current_vmptr)
 		nested_release_vmcs12(vmx);
 
+	kvm_mmu_free_roots(vcpu, &vcpu->arch.guest_mmu);
+
 	kvm_vcpu_write_guest(vcpu,
 			vmptr + offsetof(struct vmcs12, launch_state),
 			&zero, sizeof(zero));
@@ -8428,6 +8434,8 @@ static int handle_vmptrld(struct kvm_vcpu *vcpu)
 		}
 
 		nested_release_vmcs12(vmx);
+
+		kvm_mmu_free_roots(vcpu, &vcpu->arch.guest_mmu);
 		/*
 		 * Load VMCS12 from guest memory since it is not already
 		 * cached.
@@ -10244,12 +10252,12 @@ static void vmx_switch_vmcs(struct kvm_vcpu *vcpu, struct loaded_vmcs *vmcs)
  */
 static void vmx_free_vcpu_nested(struct kvm_vcpu *vcpu)
 {
-       struct vcpu_vmx *vmx = to_vmx(vcpu);
+	struct vcpu_vmx *vmx = to_vmx(vcpu);
 
-       vcpu_load(vcpu);
-       vmx_switch_vmcs(vcpu, &vmx->vmcs01);
-       free_nested(vmx);
-       vcpu_put(vcpu);
+	vcpu_load(vcpu);
+	vmx_switch_vmcs(vcpu, &vmx->vmcs01);
+	free_nested(vcpu);
+	vcpu_put(vcpu);
 }
 
 static void vmx_free_vcpu(struct kvm_vcpu *vcpu)
@@ -10573,7 +10581,9 @@ static int nested_ept_init_mmu_context(struct kvm_vcpu *vcpu)
 	if (!valid_ept_address(vcpu, nested_ept_get_cr3(vcpu)))
 		return 1;
 
-	kvm_mmu_unload(vcpu);
+	vcpu->arch.mmu = &vcpu->arch.guest_mmu;
+	kvm_mmu_free_roots(vcpu, &vcpu->arch.guest_mmu);
+
 	kvm_init_shadow_ept_mmu(vcpu,
 			to_vmx(vcpu)->nested.msrs.ept_caps &
 			VMX_EPT_EXECUTE_ONLY_BIT,
@@ -10588,6 +10598,7 @@ static int nested_ept_init_mmu_context(struct kvm_vcpu *vcpu)
 
 static void nested_ept_uninit_mmu_context(struct kvm_vcpu *vcpu)
 {
+	vcpu->arch.mmu = &vcpu->arch.root_mmu;
 	vcpu->arch.walk_mmu = &vcpu->arch.root_mmu;
 }
 
@@ -12444,7 +12455,7 @@ static void vmx_leave_nested(struct kvm_vcpu *vcpu)
 		to_vmx(vcpu)->nested.nested_run_pending = 0;
 		nested_vmx_vmexit(vcpu, -1, 0, 0);
 	}
-	free_nested(to_vmx(vcpu));
+	free_nested(vcpu);
 }
 
 /*
-- 
2.14.4