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| author | Paolo Bonzini <pbonzini@redhat.com> | 2022-11-17 20:25:02 +0300 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-11-18 19:30:12 +0300 |
| commit | 6c7b2202e4d11572ab23a89aeec49005b94bb966 (patch) | |
| tree | b47d8b0b67e8e9db088088efcfd969a48878832c /virt | |
| parent | 771a579c6e74f305eff97752d91e9b05c4e46323 (diff) | |
| download | linux-6c7b2202e4d11572ab23a89aeec49005b94bb966.tar.xz | |
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.c | 8 |
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) { |