From 07ffaf343e34b555c9e7ea39a9c81c439a706f13 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 9 Jun 2021 16:42:21 -0700 Subject: [PATCH] KVM: nVMX: Sync all PGDs on nested transition with shadow paging Trigger a full TLB flush on behalf of the guest on nested VM-Enter and VM-Exit when VPID is disabled for L2. kvm_mmu_new_pgd() syncs only the current PGD, which can theoretically leave stale, unsync'd entries in a previous guest PGD, which could be consumed if L2 is allowed to load CR3 with PCID_NOFLUSH=1. Rename KVM_REQ_HV_TLB_FLUSH to KVM_REQ_TLB_FLUSH_GUEST so that it can be utilized for its obvious purpose of emulating a guest TLB flush. Note, there is no change the actual TLB flush executed by KVM, even though the fast PGD switch uses KVM_REQ_TLB_FLUSH_CURRENT. When VPID is disabled for L2, vpid02 is guaranteed to be '0', and thus nested_get_vpid02() will return the VPID that is shared by L1 and L2. Generate the request outside of kvm_mmu_new_pgd(), as getting the common helper to correctly identify which requested is needed is quite painful. E.g. using KVM_REQ_TLB_FLUSH_GUEST when nested EPT is in play is wrong as a TLB flush from the L1 kernel's perspective does not invalidate EPT mappings. And, by using KVM_REQ_TLB_FLUSH_GUEST, nVMX can do future simplification by moving the logic into nested_vmx_transition_tlb_flush(). Fixes: 41fab65e7c44 ("KVM: nVMX: Skip MMU sync on nested VMX transition when possible") Signed-off-by: Sean Christopherson Message-Id: <20210609234235.1244004-2-seanjc@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/include/asm/kvm_host.h | 2 +- arch/x86/kvm/hyperv.c | 2 +- arch/x86/kvm/vmx/nested.c | 17 ++++++++++++----- arch/x86/kvm/x86.c | 2 +- 4 files changed, 15 insertions(+), 8 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 3831069..f44a979 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -85,7 +85,7 @@ #define KVM_REQ_APICV_UPDATE \ KVM_ARCH_REQ_FLAGS(25, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP) #define KVM_REQ_TLB_FLUSH_CURRENT KVM_ARCH_REQ(26) -#define KVM_REQ_HV_TLB_FLUSH \ +#define KVM_REQ_TLB_FLUSH_GUEST \ KVM_ARCH_REQ_FLAGS(27, KVM_REQUEST_NO_WAKEUP) #define KVM_REQ_APF_READY KVM_ARCH_REQ(28) #define KVM_REQ_MSR_FILTER_CHANGED KVM_ARCH_REQ(29) diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index 4f911dc..b07592c 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -1829,7 +1829,7 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc, bool * vcpu->arch.cr3 may not be up-to-date for running vCPUs so we can't * analyze it here, flush TLB regardless of the specified address space. */ - kvm_make_vcpus_request_mask(kvm, KVM_REQ_HV_TLB_FLUSH, + kvm_make_vcpus_request_mask(kvm, KVM_REQ_TLB_FLUSH_GUEST, NULL, vcpu_mask, &hv_vcpu->tlb_flush); ret_success: diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index ee89b48..a9906c8 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -1131,12 +1131,19 @@ static int nested_vmx_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, /* * Unconditionally skip the TLB flush on fast CR3 switch, all TLB - * flushes are handled by nested_vmx_transition_tlb_flush(). See - * nested_vmx_transition_mmu_sync for details on skipping the MMU sync. + * flushes are handled by nested_vmx_transition_tlb_flush(). */ - if (!nested_ept) - kvm_mmu_new_pgd(vcpu, cr3, true, - !nested_vmx_transition_mmu_sync(vcpu)); + if (!nested_ept) { + kvm_mmu_new_pgd(vcpu, cr3, true, true); + + /* + * A TLB flush on VM-Enter/VM-Exit flushes all linear mappings + * across all PCIDs, i.e. all PGDs need to be synchronized. + * See nested_vmx_transition_mmu_sync() for more details. + */ + if (nested_vmx_transition_mmu_sync(vcpu)) + kvm_make_request(KVM_REQ_TLB_FLUSH_GUEST, vcpu); + } vcpu->arch.cr3 = cr3; kvm_register_mark_available(vcpu, VCPU_EXREG_CR3); diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 1727178..efcdd1f 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9279,7 +9279,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) } if (kvm_check_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu)) kvm_vcpu_flush_tlb_current(vcpu); - if (kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu)) + if (kvm_check_request(KVM_REQ_TLB_FLUSH_GUEST, vcpu)) kvm_vcpu_flush_tlb_guest(vcpu); if (kvm_check_request(KVM_REQ_REPORT_TPR_ACCESS, vcpu)) { -- 2.7.4