diff options
| -rw-r--r-- | arch/x86/kvm/mmu/mmu.c | 22 | ||||
| -rw-r--r-- | include/linux/kvm_host.h | 5 | ||||
| -rw-r--r-- | virt/kvm/kvm_main.c | 8 |
3 files changed, 32 insertions, 3 deletions
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index cfff74685a25..4736d7849c60 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -6878,16 +6878,32 @@ static void kvm_recover_nx_huge_pages(struct kvm *kvm) WARN_ON_ONCE(!sp->nx_huge_page_disallowed); WARN_ON_ONCE(!sp->role.direct); - slot = gfn_to_memslot(kvm, sp->gfn); - WARN_ON_ONCE(!slot); - /* * Unaccount and do not attempt to recover any NX Huge Pages * that are being dirty tracked, as they would just be faulted * back in as 4KiB pages. The NX Huge Pages in this slot will be * recovered, along with all the other huge pages in the slot, * when dirty logging is disabled. + * + * Since gfn_to_memslot() is relatively expensive, it helps to + * skip it if it the test cannot possibly return true. On the + * other hand, if any memslot has logging enabled, chances are + * good that all of them do, in which case unaccount_nx_huge_page() + * is much cheaper than zapping the page. + * + * If a memslot update is in progress, reading an incorrect value + * of kvm->nr_memslots_dirty_logging is not a problem: if it is + * becoming zero, gfn_to_memslot() will be done unnecessarily; if + * it is becoming nonzero, the page will be zapped unnecessarily. + * Either way, this only affects efficiency in racy situations, + * and not correctness. */ + slot = NULL; + if (atomic_read(&kvm->nr_memslots_dirty_logging)) { + slot = gfn_to_memslot(kvm, sp->gfn); + WARN_ON_ONCE(!slot); + } + if (slot && kvm_slot_dirty_track_enabled(slot)) unaccount_nx_huge_page(kvm, sp); else if (is_tdp_mmu_page(sp)) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index e6e66c5e56f2..6f0f389f5f9c 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -722,6 +722,11 @@ struct kvm { /* The current active memslot set for each address space */ struct kvm_memslots __rcu *memslots[KVM_ADDRESS_SPACE_NUM]; struct xarray vcpu_array; + /* + * Protected by slots_lock, but can be read outside if an + * incorrect answer is acceptable. + */ + atomic_t nr_memslots_dirty_logging; /* Used to wait for completion of MMU notifiers. */ spinlock_t mn_invalidate_lock; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 43bbe4fde078..1782c4555d94 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1641,6 +1641,8 @@ static void kvm_commit_memory_region(struct kvm *kvm, const struct kvm_memory_slot *new, enum kvm_mr_change change) { + int old_flags = old ? old->flags : 0; + int new_flags = new ? new->flags : 0; /* * Update the total number of memslot pages before calling the arch * hook so that architectures can consume the result directly. @@ -1650,6 +1652,12 @@ static void kvm_commit_memory_region(struct kvm *kvm, else if (change == KVM_MR_CREATE) kvm->nr_memslot_pages += new->npages; + if ((old_flags ^ new_flags) & KVM_MEM_LOG_DIRTY_PAGES) { + int change = (new_flags & KVM_MEM_LOG_DIRTY_PAGES) ? 1 : -1; + atomic_set(&kvm->nr_memslots_dirty_logging, + atomic_read(&kvm->nr_memslots_dirty_logging) + change); + } + kvm_arch_commit_memory_region(kvm, old, new, change); switch (change) { |