KVM: x86/mmu: Skip MMIO SPTE invalidation if enable_mmio_caching=0

If MMIO caching is disabled, there are no MMIO SPTEs to invalidate, so
the costly zapping of all pages is unnecessary even in the unlikely case
when the MMIO generation number has wrapped.

Signed-off-by: Dmytro Maluka <dmaluka@chromium.org>
Link: https://lore.kernel.org/r/20250926135139.1597781-1-dmaluka@chromium.org
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 667d66cf76d5e52c22f9517914307244ae868eea..18d69d48bc55ac09bb2687e9a62ab14534742e08 100644 (file)
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -7364,6 +7364,9 @@ void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, u64 gen)
 {
        WARN_ON_ONCE(gen & KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS);
 
+       if (!enable_mmio_caching)
+               return;
+
        gen &= MMIO_SPTE_GEN_MASK;
 
        /*