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Subject[PATCH 1/2] KVM: x86: allow kvm_tdp_mmu_zap_invalidated_roots with write-locked mmu_lock
Date
Zapping within a write-side critical section is more efficient, so it is
desirable if we know that no vCPU is running (such as within the .release
MMU notifier callback). Prepare for reusing kvm_tdp_mmu_zap_invalidated_roots
in such scenarios.

Fixes: b7cccd397f31 ("KVM: x86/mmu: Fast invalidation for TDP MMU")
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/mmu/mmu.c | 2 +-
arch/x86/kvm/mmu/tdp_mmu.c | 17 +++++++++--------
arch/x86/kvm/mmu/tdp_mmu.h | 2 +-
3 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 4a3bcdd3cfe7..6fe4ab8fc0ca 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5695,7 +5695,7 @@ static void kvm_mmu_zap_all_fast(struct kvm *kvm)

if (is_tdp_mmu_enabled(kvm)) {
read_lock(&kvm->mmu_lock);
- kvm_tdp_mmu_zap_invalidated_roots(kvm);
+ kvm_tdp_mmu_zap_invalidated_roots(kvm, true);
read_unlock(&kvm->mmu_lock);
}
}
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 1db8496259ad..f2dd5c97bbc2 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -821,14 +821,18 @@ static struct kvm_mmu_page *next_invalidated_root(struct kvm *kvm,
* only has to do a trivial amount of work. Since the roots are invalid,
* no new SPTEs should be created under them.
*/
-void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm)
+void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm, bool shared)
{
struct kvm_mmu_page *next_root;
struct kvm_mmu_page *root;
bool flush = false;

- lockdep_assert_held_read(&kvm->mmu_lock);
+ kvm_lockdep_assert_mmu_lock_held(kvm, shared);

+ /*
+ * rcu_read_lock is only needed for shared == true, but we
+ * always take it for simplicity.
+ */
rcu_read_lock();

root = next_invalidated_root(kvm, NULL);
@@ -838,13 +842,10 @@ void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm)

rcu_read_unlock();

- flush = zap_gfn_range(kvm, root, 0, -1ull, true, flush, true);
+ flush = zap_gfn_range(kvm, root, 0, -1ull, true, flush, shared);

- /*
- * Put the reference acquired in
- * kvm_tdp_mmu_invalidate_roots
- */
- kvm_tdp_mmu_put_root(kvm, root, true);
+ /* Put the reference acquired in kvm_tdp_mmu_invalidate_roots. */
+ kvm_tdp_mmu_put_root(kvm, root, shared);

root = next_root;

diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h
index 3899004a5d91..24809f4ed090 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.h
+++ b/arch/x86/kvm/mmu/tdp_mmu.h
@@ -46,7 +46,7 @@ static inline bool kvm_tdp_mmu_zap_sp(struct kvm *kvm, struct kvm_mmu_page *sp)

void kvm_tdp_mmu_zap_all(struct kvm *kvm);
void kvm_tdp_mmu_invalidate_all_roots(struct kvm *kvm);
-void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm);
+void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm, bool shared);

int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault);

--
2.31.1

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