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From:   Paolo Bonzini <pbonzini@redhat.com>
To:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc:     Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        David Hildenbrand <david@redhat.com>,
        David Matlack <dmatlack@google.com>,
        Ben Gardon <bgardon@google.com>,
        Mingwei Zhang <mizhang@google.com>
Subject: [PATCH v4 06/30] KVM: x86/mmu: only perform eager page splitting on valid roots
Date:   Thu,  3 Mar 2022 14:38:18 -0500
Message-Id: <20220303193842.370645-7-pbonzini@redhat.com>
In-Reply-To: <20220303193842.370645-1-pbonzini@redhat.com>
References: <20220303193842.370645-1-pbonzini@redhat.com>
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Eager page splitting is an optimization; it does not have to be performed on
invalid roots.  It is also the only case in which a reader might acquire
a reference to an invalid root, so after this change we know that readers
will skip both dying and invalid roots.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/kvm/mmu/tdp_mmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 30424fbceb5f..d39593b9ac9e 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -1464,7 +1464,7 @@ void kvm_tdp_mmu_try_split_huge_pages(struct kvm *kvm,
 
 	kvm_lockdep_assert_mmu_lock_held(kvm, shared);
 
-	for_each_tdp_mmu_root_yield_safe(kvm, root, slot->as_id, shared) {
+	for_each_valid_tdp_mmu_root_yield_safe(kvm, root, slot->as_id, shared) {
 		r = tdp_mmu_split_huge_pages_root(kvm, root, start, end, target_level, shared);
 		if (r) {
 			kvm_tdp_mmu_put_root(kvm, root, shared);
-- 
2.31.1