linux-kernel - [PATCH MANUALSEL 5.15 3/8] KVM: X86: Don't check unsync if the original spte is writible

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Message-Id: <20211123163630.289306-3-sashal@kernel.org>
Date:   Tue, 23 Nov 2021 11:36:25 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Lai Jiangshan <laijs@...ux.alibaba.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sasha Levin <sashal@...nel.org>, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        x86@...nel.org, kvm@...r.kernel.org
Subject: [PATCH MANUALSEL 5.15 3/8] KVM: X86: Don't check unsync if the original spte is writible

From: Lai Jiangshan <laijs@...ux.alibaba.com>

[ Upstream commit 8b8f9d753b84c243bf0b1004b515c53b7ec7e138 ]

If the original spte is writable, the target gfn should not be the
gfn of synchronized shadowpage and can continue to be writable.

When !can_unsync, speculative must be false.  So when the check of
"!can_unsync" is removed, we need to move the label of "out" up.

Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Message-Id: <20210918005636.3675-11-jiangshanlai@...il.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/kvm/mmu/spte.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c
index 3e97cdb13eb7e..86a21eb85d25f 100644
--- a/arch/x86/kvm/mmu/spte.c
+++ b/arch/x86/kvm/mmu/spte.c
@@ -150,7 +150,7 @@ int make_spte(struct kvm_vcpu *vcpu, unsigned int pte_access, int level,
 		 * is responsibility of kvm_mmu_get_page / kvm_mmu_sync_roots.
 		 * Same reasoning can be applied to dirty page accounting.
 		 */
-		if (!can_unsync && is_writable_pte(old_spte))
+		if (is_writable_pte(old_spte))
 			goto out;
 
 		/*
@@ -171,10 +171,10 @@ int make_spte(struct kvm_vcpu *vcpu, unsigned int pte_access, int level,
 	if (pte_access & ACC_WRITE_MASK)
 		spte |= spte_shadow_dirty_mask(spte);
 
+out:
 	if (speculative)
 		spte = mark_spte_for_access_track(spte);
 
-out:
 	WARN_ONCE(is_rsvd_spte(&vcpu->arch.mmu->shadow_zero_check, spte, level),
 		  "spte = 0x%llx, level = %d, rsvd bits = 0x%llx", spte, level,
 		  get_rsvd_bits(&vcpu->arch.mmu->shadow_zero_check, spte, level));
-- 
2.33.0