Re: [PATCH 10/13] KVM: x86/mmu: Allow zapping collapsible SPTEs to use MMU read lock

[Paolo Bonzini]

On 31/03/21 23:08, Ben Gardon wrote:

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index dcbfc784cf2f..81967b4e7d76 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5610,10 +5610,13 @@ void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm,

write_lock(&kvm->mmu_lock);

        slot_handle_leaf(kvm, slot, kvm_mmu_zap_collapsible_spte, true);
-
-       if (is_tdp_mmu_enabled(kvm))
-               kvm_tdp_mmu_zap_collapsible_sptes(kvm, slot);
        write_unlock(&kvm->mmu_lock);
+
+       if (is_tdp_mmu_enabled(kvm)) {
+               read_lock(&kvm->mmu_lock);
+               kvm_tdp_mmu_zap_collapsible_sptes(kvm, memslot);
+               read_unlock(&kvm->mmu_lock);
+       }
  }

Same here, this will conflict with

KVM: x86/mmu: Coalesce TLB flushes when zapping collapsible SPTEs

Again, you will have to add back some "if (flush)" before the write_unlock.

Paolo