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From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: kvm@vger.kernel.org
Cc: "Paolo Bonzini" <pbonzini@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	"Jim Mattson" <jmattson@google.com>,
	"Liran Alon" <liran.alon@oracle.com>,
	linux-kernel@vger.kernel.org
Subject: [PATCH v1 RESEND 4/9] x86/kvm/mmu: introduce guest_mmu
Date: Tue, 18 Sep 2018 18:09:01 +0200	[thread overview]
Message-ID: <20180918160906.9241-5-vkuznets@redhat.com> (raw)
In-Reply-To: <20180918160906.9241-1-vkuznets@redhat.com>

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 use
separate root caches; the improved hit rate is not very important for
single vCPU performance, but it avoids contention on the mmu_lock for
many vCPUs.

On the nested CPUID benchmark, with 16 vCPUs, an L2->L1->L2 vmexit
goes from 42k to 26k cycles.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/include/asm/kvm_host.h |  3 +++
 arch/x86/kvm/mmu.c              | 15 +++++++++++----
 arch/x86/kvm/vmx.c              | 27 +++++++++++++++++++--------
 3 files changed, 33 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index fc6038b4ed6b..3f53235ee2a8 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -539,6 +539,9 @@ 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 113feceec686..96593cd285db 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4967,8 +4967,10 @@ EXPORT_SYMBOL_GPL(kvm_mmu_load);
 
 void kvm_mmu_unload(struct kvm_vcpu *vcpu)
 {
-	kvm_mmu_free_roots(vcpu, vcpu->arch.mmu, KVM_MMU_ROOTS_ALL);
-	WARN_ON(VALID_PAGE(vcpu->arch.mmu->root_hpa));
+	kvm_mmu_free_roots(vcpu, &vcpu->arch.root_mmu, KVM_MMU_ROOTS_ALL);
+	WARN_ON(VALID_PAGE(vcpu->arch.root_mmu.root_hpa));
+	kvm_mmu_free_roots(vcpu, &vcpu->arch.guest_mmu, KVM_MMU_ROOTS_ALL);
+	WARN_ON(VALID_PAGE(vcpu->arch.guest_mmu.root_hpa));
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_unload);
 
@@ -5407,13 +5409,18 @@ 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.root_mmu.root_hpa = INVALID_PAGE;
 	vcpu->arch.root_mmu.translate_gpa = translate_gpa;
-	vcpu->arch.nested_mmu.translate_gpa = translate_nested_gpa;
-
 	for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
 		vcpu->arch.root_mmu.prev_roots[i] = KVM_MMU_ROOT_INFO_INVALID;
 
+	vcpu->arch.guest_mmu.root_hpa = INVALID_PAGE;
+	vcpu->arch.guest_mmu.translate_gpa = translate_gpa;
+	for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
+		vcpu->arch.guest_mmu.prev_roots[i] = KVM_MMU_ROOT_INFO_INVALID;
+
+	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 0e56b2237a42..29af40b9239f 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8438,8 +8438,10 @@ 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;
 
@@ -8472,6 +8474,8 @@ static void free_nested(struct vcpu_vmx *vmx)
 		vmx->nested.pi_desc = NULL;
 	}
 
+	kvm_mmu_free_roots(vcpu, &vcpu->arch.guest_mmu, KVM_MMU_ROOTS_ALL);
+
 	free_loaded_vmcs(&vmx->nested.vmcs02);
 }
 
@@ -8480,7 +8484,7 @@ 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);
 }
@@ -8511,6 +8515,8 @@ 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_MMU_ROOTS_ALL);
+
 	kvm_vcpu_write_guest(vcpu,
 			vmptr + offsetof(struct vmcs12, launch_state),
 			&zero, sizeof(zero));
@@ -8894,6 +8900,9 @@ static int handle_vmptrld(struct kvm_vcpu *vcpu)
 		}
 
 		nested_release_vmcs12(vmx);
+
+		kvm_mmu_free_roots(vcpu, &vcpu->arch.guest_mmu,
+				   KVM_MMU_ROOTS_ALL);
 		/*
 		 * Load VMCS12 from guest memory since it is not already
 		 * cached.
@@ -10926,12 +10935,12 @@ 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)
@@ -11281,6 +11290,7 @@ static int nested_ept_init_mmu_context(struct kvm_vcpu *vcpu)
 	if (!valid_ept_address(vcpu, nested_ept_get_cr3(vcpu)))
 		return 1;
 
+	vcpu->arch.mmu = &vcpu->arch.guest_mmu;
 	kvm_init_shadow_ept_mmu(vcpu,
 			to_vmx(vcpu)->nested.msrs.ept_caps &
 			VMX_EPT_EXECUTE_ONLY_BIT,
@@ -11296,6 +11306,7 @@ 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;
 }
 
@@ -13363,7 +13374,7 @@ 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


  parent reply	other threads:[~2018-09-18 16:09 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-18 16:08 [PATCH v1 RESEND 0/9] x86/kvm/nVMX: optimize MMU switch between L1 and L2 Vitaly Kuznetsov
2018-09-18 16:08 ` [PATCH v1 RESEND 1/9] x86/kvm/mmu: make vcpu->mmu a pointer to the current MMU Vitaly Kuznetsov
2018-09-18 16:08 ` [PATCH v1 RESEND 2/9] x86/kvm/mmu.c: set get_pdptr hook in kvm_init_shadow_ept_mmu() Vitaly Kuznetsov
2018-09-18 16:09 ` [PATCH v1 RESEND 3/9] x86/kvm/mmu.c: add kvm_mmu parameter to kvm_mmu_free_roots() Vitaly Kuznetsov
2018-09-18 16:09 ` Vitaly Kuznetsov [this message]
2018-09-19 15:08   ` [PATCH v1 RESEND 4/9] x86/kvm/mmu: introduce guest_mmu Sean Christopherson
2018-09-18 16:09 ` [PATCH v1 RESEND 5/9] x86/kvm/mmu: get rid of redundant kvm_mmu_setup() Vitaly Kuznetsov
2018-09-18 16:09 ` [PATCH v1 RESEND 6/9] x86/kvm/mmu: make space for source data caching in struct kvm_mmu Vitaly Kuznetsov
2018-09-19 15:30   ` Sean Christopherson
2018-09-18 16:09 ` [PATCH v1 RESEND 7/9] x86/kvm/nVMX: introduce scache for kvm_init_shadow_ept_mmu Vitaly Kuznetsov
2018-09-18 16:09 ` [PATCH v1 RESEND 8/9] x86/kvm/mmu: check if tdp/shadow MMU reconfiguration is needed Vitaly Kuznetsov
2018-09-18 16:09 ` [PATCH v1 RESEND 9/9] x86/kvm/mmu: check if MMU reconfiguration is needed in init_kvm_nested_mmu() Vitaly Kuznetsov

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