[PATCH v4 09/30] KVM: x86/mmu: Batch TLB flushes from TDP MMU for MMU notifier change_spte

[Paolo Bonzini]

From: Sean Christopherson <seanjc@xxxxxxxxxx>

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@xxxxxxxxxx>
Reviewed-by: Ben Gardon <bgardon@xxxxxxxxxx>
Message-Id: <20220226001546.360188-9-seanjc@xxxxxxxxxx>
Reviewed-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 arch/x86/kvm/mmu/tdp_mmu.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 53c7987198b7..9b1d64468d95 100644
--- 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);
 }
 
 /*
-- 
2.31.1