[PATCH 5/5] KVM: VMX: Sketch in possible framework for eliding TLB flushes on pCPU migration

[Sean Christopherson <seanjc@xxxxxxxxxx>]

Not-Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>

(anyone that makes this work deserves full credit)
---
 arch/x86/kvm/mmu/mmu.c     |  3 +++
 arch/x86/kvm/mmu/tdp_mmu.c |  2 ++
 arch/x86/kvm/vmx/vmx.c     | 21 ++++++++++++++-------
 3 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 6e838cb6c9e1..925efbaae9b9 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3854,6 +3854,9 @@ static hpa_t mmu_alloc_root(struct kvm_vcpu *vcpu, gfn_t gfn, int quadrant,
 	sp = kvm_mmu_get_shadow_page(vcpu, gfn, role);
 	++sp->root_count;
 
+	if (level >= PT64_ROOT_4LEVEL)
+		kvm_x86_call(alloc_root_cpu_mask)(root);
+
 	return __pa(sp->spt);
 }
 
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 7f3d7229b2c1..bf4b0b9a7816 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -293,6 +293,8 @@ void kvm_tdp_mmu_alloc_root(struct kvm_vcpu *vcpu, bool mirror)
 	root = tdp_mmu_alloc_sp(vcpu);
 	tdp_mmu_init_sp(root, NULL, 0, role);
 
+	kvm_x86_call(alloc_root_cpu_mask)(root);
+
 	/*
 	 * TDP MMU roots are kept until they are explicitly invalidated, either
 	 * by a memslot update or by the destruction of the VM.  Initialize the
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index b42747e2293d..e85830189cfc 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1395,7 +1395,7 @@ static void shrink_ple_window(struct kvm_vcpu *vcpu)
 	}
 }
 
-static void vmx_flush_ept_on_pcpu_migration(struct kvm_mmu *mmu);
+static void vmx_flush_ept_on_pcpu_migration(struct kvm_mmu *mmu, int cpu);
 
 void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu)
 {
@@ -1434,8 +1434,8 @@ void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu)
 		 * TLB entries from its previous association with the vCPU.
 		 */
 		if (enable_ept) {
-			vmx_flush_ept_on_pcpu_migration(&vcpu->arch.root_mmu);
-			vmx_flush_ept_on_pcpu_migration(&vcpu->arch.guest_mmu);
+			vmx_flush_ept_on_pcpu_migration(&vcpu->arch.root_mmu, cpu);
+			vmx_flush_ept_on_pcpu_migration(&vcpu->arch.guest_mmu, cpu);
 		} else {
 			kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
 		}
@@ -3261,22 +3261,29 @@ void vmx_flush_tlb_guest(struct kvm_vcpu *vcpu)
 	vpid_sync_context(vmx_get_current_vpid(vcpu));
 }
 
-static void __vmx_flush_ept_on_pcpu_migration(hpa_t root_hpa)
+static void __vmx_flush_ept_on_pcpu_migration(hpa_t root_hpa, int cpu)
 {
+	struct kvm_mmu_page *root;
+
 	if (!VALID_PAGE(root_hpa))
 		return;
 
+	root = root_to_sp(root_hpa);
+	if (!WARN_ON_ONCE(!root) &&
+	    test_and_set_bit(cpu, root->cpu_flushed_mask))
+		return;
+
 	vmx_flush_tlb_ept_root(root_hpa);
 }
 
-static void vmx_flush_ept_on_pcpu_migration(struct kvm_mmu *mmu)
+static void vmx_flush_ept_on_pcpu_migration(struct kvm_mmu *mmu, int cpu)
 {
 	int i;
 
-	__vmx_flush_ept_on_pcpu_migration(mmu->root.hpa);
+	__vmx_flush_ept_on_pcpu_migration(mmu->root.hpa, cpu);
 
 	for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
-		__vmx_flush_ept_on_pcpu_migration(mmu->prev_roots[i].hpa);
+		__vmx_flush_ept_on_pcpu_migration(mmu->prev_roots[i].hpa, cpu);
 }
 
 void vmx_ept_load_pdptrs(struct kvm_vcpu *vcpu)
-- 
2.50.1.565.gc32cd1483b-goog


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