KVM: x86/mmu: Batch TLB flushes from TDP MMU for MMU notifier change_spte

Batch TLB flushes (with other MMUs) when handling ->change_spte()
notifications in the TDP MMU.  The MMU notifier path in question doesn't
allow yielding and correcty flushes before dropping mmu_lock.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Ben Gardon <bgardon@google.com>
Message-Id: <20220226001546.360188-9-seanjc@google.com>
Reviewed-by: Mingwei Zhang <mizhang@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 53c7987..9b1d644 100644 (file)
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -1226,13 +1226,12 @@ static bool set_spte_gfn(struct kvm *kvm, struct tdp_iter *iter,
  */
 bool kvm_tdp_mmu_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
 {
-       bool flush = kvm_tdp_mmu_handle_gfn(kvm, range, set_spte_gfn);
-
-       /* FIXME: return 'flush' instead of flushing here. */
-       if (flush)
-               kvm_flush_remote_tlbs_with_address(kvm, range->start, 1);
-
-       return false;
+       /*
+        * No need to handle the remote TLB flush under RCU protection, the
+        * target SPTE _must_ be a leaf SPTE, i.e. cannot result in freeing a
+        * shadow page.  See the WARN on pfn_changed in __handle_changed_spte().
+        */
+       return kvm_tdp_mmu_handle_gfn(kvm, range, set_spte_gfn);
 }
 
 /*