KVM: x86/mmu: Fast invalidation for TDP MMU
Provide a real mechanism for fast invalidation by marking roots as
invalid so that their reference count will quickly fall to zero
and they will be torn down.
One negative side affect of this approach is that a vCPU thread will
likely drop the last reference to a root and be saddled with the work of
tearing down an entire paging structure. This issue will be resolved in
a later commit.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-13-bgardon@google.com>
[Move the loop to tdp_mmu.c, otherwise compilation fails on 32-bit. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 61c0d10..3323ab2 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5421,6 +5421,15 @@ static void kvm_mmu_zap_all_fast(struct kvm *kvm)
*/
kvm->arch.mmu_valid_gen = kvm->arch.mmu_valid_gen ? 0 : 1;
+ /* In order to ensure all threads see this change when
+ * handling the MMU reload signal, this must happen in the
+ * same critical section as kvm_reload_remote_mmus, and
+ * before kvm_zap_obsolete_pages as kvm_zap_obsolete_pages
+ * could drop the MMU lock and yield.
+ */
+ if (is_tdp_mmu_enabled(kvm))
+ kvm_tdp_mmu_invalidate_all_roots(kvm);
+
/*
* Notify all vcpus to reload its shadow page table and flush TLB.
* Then all vcpus will switch to new shadow page table with the new
@@ -5433,9 +5442,6 @@ static void kvm_mmu_zap_all_fast(struct kvm *kvm)
kvm_zap_obsolete_pages(kvm);
- if (is_tdp_mmu_enabled(kvm))
- kvm_tdp_mmu_zap_all(kvm);
-
write_unlock(&kvm->mmu_lock);
}