linux-kernel - [PATCH 1/7] KVM: X86: Fix missed remote tlb flush in rmap_write

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Message-Id: <20210824075524.3354-2-jiangshanlai@gmail.com>
Date:   Tue, 24 Aug 2021 15:55:17 +0800
From:   Lai Jiangshan <jiangshanlai@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Lai Jiangshan <laijs@...ux.alibaba.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Avi Kivity <avi@...hat.com>, kvm@...r.kernel.org
Subject: [PATCH 1/7] KVM: X86: Fix missed remote tlb flush in rmap_write_protect()

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

When kvm->tlbs_dirty > 0, some rmaps might have been deleted
without flushing tlb remotely after kvm_sync_page().  If @gfn
was writable before and it's rmaps was deleted in kvm_sync_page(),
we need to flush tlb too even if __rmap_write_protect() doesn't
request it.

Fixes: 4731d4c7a077 ("KVM: MMU: out of sync shadow core")
Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>
---
 arch/x86/kvm/mmu/mmu.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 4853c033e6ce..313918df1a10 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -1420,6 +1420,14 @@ bool kvm_mmu_slot_gfn_write_protect(struct kvm *kvm,
 			rmap_head = gfn_to_rmap(gfn, i, slot);
 			write_protected |= __rmap_write_protect(kvm, rmap_head, true);
 		}
+		/*
+		 * When kvm->tlbs_dirty > 0, some rmaps might have been deleted
+		 * without flushing tlb remotely after kvm_sync_page().  If @gfn
+		 * was writable before and it's rmaps was deleted in kvm_sync_page(),
+		 * we need to flush tlb too.
+		 */
+		if (min_level == PG_LEVEL_4K && kvm->tlbs_dirty)
+			write_protected = true;
 	}
 
 	if (is_tdp_mmu_enabled(kvm))
@@ -5733,6 +5741,14 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm,
 		flush = slot_handle_level(kvm, memslot, slot_rmap_write_protect,
 					  start_level, KVM_MAX_HUGEPAGE_LEVEL,
 					  false);
+		/*
+		 * When kvm->tlbs_dirty > 0, some rmaps might have been deleted
+		 * without flushing tlb remotely after kvm_sync_page().  If @gfn
+		 * was writable before and it's rmaps was deleted in kvm_sync_page(),
+		 * we need to flush tlb too.
+		 */
+		if (start_level == PG_LEVEL_4K && kvm->tlbs_dirty)
+			flush = true;
 		write_unlock(&kvm->mmu_lock);
 	}
 
-- 
2.19.1.6.gb485710b