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From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
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>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Ben Gardon <bgardon@google.com>
Subject: [PATCH 1/2] KVM: x86/mmu: Remove spurious clearing of dirty bit from TDP MMU SPTE
Date: Tue, 30 Mar 2021 17:49:41 -0700	[thread overview]
Message-ID: <20210331004942.2444916-2-seanjc@google.com> (raw)
In-Reply-To: <20210331004942.2444916-1-seanjc@google.com>

Don't clear the dirty bit when aging a TDP MMU SPTE (in response to a MMU
notifier event).  Prematurely clearing the dirty bit could cause spurious
PML updates if aging a page happened to coincide with dirty logging.

Note, tdp_mmu_set_spte_no_acc_track() flows into __handle_changed_spte(),
so the host PFN will be marked dirty, i.e. there is no potential for data
corruption.

Fixes: a6a0b05da9f3 ("kvm: x86/mmu: Support dirty logging for the TDP MMU")
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/mmu/tdp_mmu.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index f0c99fa04ef2..724088bea4b0 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -978,7 +978,6 @@ static int age_gfn_range(struct kvm *kvm, struct kvm_memory_slot *slot,
 
 			new_spte = mark_spte_for_access_track(new_spte);
 		}
-		new_spte &= ~shadow_dirty_mask;
 
 		tdp_mmu_set_spte_no_acc_track(kvm, &iter, new_spte);
 		young = 1;
-- 
2.31.0.291.g576ba9dcdaf-goog


  reply	other threads:[~2021-03-31  0:50 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-31  0:49 [PATCH 0/2] KVM: x86/mmu: TDP MMU fixes/cleanups Sean Christopherson
2021-03-31  0:49 ` Sean Christopherson [this message]
2021-03-31  0:49 ` [PATCH 2/2] KVM: x86/mmu: Simplify code for aging SPTEs in TDP MMU Sean Christopherson
2021-03-31  9:36 ` [PATCH 0/2] KVM: x86/mmu: TDP MMU fixes/cleanups Paolo Bonzini

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