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authorPaolo Bonzini <pbonzini@redhat.com>2022-11-17 12:25:02 -0500
committerPaolo Bonzini <pbonzini@redhat.com>2022-11-18 11:30:12 -0500
commit6c7b2202e4d11572ab23a89aeec49005b94bb966 (patch)
treeb47d8b0b67e8e9db088088efcfd969a48878832c /virt
parent771a579c6e74f305eff97752d91e9b05c4e46323 (diff)
KVM: x86: avoid memslot check in NX hugepage recovery if it cannot succeed
Since gfn_to_memslot() is relatively expensive, it helps to skip it if it the memslot cannot possibly have dirty logging enabled. In order to do this, add to struct kvm a counter of the number of log-page memslots. While the correct value can only be read with slots_lock taken, the NX recovery thread is content with using an approximate value. Therefore, the counter is an atomic_t. Based on https://lore.kernel.org/kvm/20221027200316.2221027-2-dmatlack@google.com/ by David Matlack. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/kvm_main.c8
1 files changed, 8 insertions, 0 deletions
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) {