diff options
| -rw-r--r-- | arch/x86/kvm/mmu/mmu.c | 10 | ||||
| -rw-r--r-- | arch/x86/kvm/mmu/tdp_mmu.c | 15 |
2 files changed, 17 insertions, 8 deletions
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 43f92b111d7b..a3154f33e803 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -5685,9 +5685,13 @@ restart: } /* - * Trigger a remote TLB flush before freeing the page tables to ensure - * KVM is not in the middle of a lockless shadow page table walk, which - * may reference the pages. + * Kick all vCPUs (via remote TLB flush) before freeing the page tables + * to ensure KVM is not in the middle of a lockless shadow page table + * walk, which may reference the pages. The remote TLB flush itself is + * not required and is simply a convenient way to kick vCPUs as needed. + * KVM performs a local TLB flush when allocating a new root (see + * kvm_mmu_load()), and the reload in the caller ensure no vCPUs are + * running with an obsolete MMU. */ kvm_mmu_commit_zap_page(kvm, &kvm->arch.zapped_obsolete_pages); } diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 921fa386df99..2ce6915b70fe 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -851,7 +851,6 @@ void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm) { struct kvm_mmu_page *next_root; struct kvm_mmu_page *root; - bool flush = false; lockdep_assert_held_read(&kvm->mmu_lock); @@ -864,7 +863,16 @@ void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm) rcu_read_unlock(); - flush = zap_gfn_range(kvm, root, 0, -1ull, true, flush, true); + /* + * A TLB flush is unnecessary, invalidated roots are guaranteed + * to be unreachable by the guest (see kvm_tdp_mmu_put_root() + * for more details), and unlike the legacy MMU, no vCPU kick + * is needed to play nice with lockless shadow walks as the TDP + * MMU protects its paging structures via RCU. Note, zapping + * will still flush on yield, but that's a minor performance + * blip and not a functional issue. + */ + (void)zap_gfn_range(kvm, root, 0, -1ull, true, false, true); /* * Put the reference acquired in @@ -878,9 +886,6 @@ void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm) } rcu_read_unlock(); - - if (flush) - kvm_flush_remote_tlbs(kvm); } /* |