linux-kernel - [PATCH v12 64/84] KVM: LoongArch: Mark "struct page" pfns dirty only in "slow" page fault path

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20240726235234.228822-65-seanjc@google.com>
Date: Fri, 26 Jul 2024 16:52:13 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>, 
	Oliver Upton <oliver.upton@...ux.dev>, Tianrui Zhao <zhaotianrui@...ngson.cn>, 
	Bibo Mao <maobibo@...ngson.cn>, Huacai Chen <chenhuacai@...nel.org>, 
	Michael Ellerman <mpe@...erman.id.au>, Anup Patel <anup@...infault.org>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, Christian Borntraeger <borntraeger@...ux.ibm.com>, 
	Janosch Frank <frankja@...ux.ibm.com>, Claudio Imbrenda <imbrenda@...ux.ibm.com>, 
	Sean Christopherson <seanjc@...gle.com>
Cc: kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	kvmarm@...ts.linux.dev, loongarch@...ts.linux.dev, linux-mips@...r.kernel.org, 
	linuxppc-dev@...ts.ozlabs.org, kvm-riscv@...ts.infradead.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	David Matlack <dmatlack@...gle.com>, David Stevens <stevensd@...omium.org>
Subject: [PATCH v12 64/84] KVM: LoongArch: Mark "struct page" pfns dirty only
 in "slow" page fault path

Mark pages/folios dirty only the slow page fault path, i.e. only when
mmu_lock is held and the operation is mmu_notifier-protected, as marking a
page/folio dirty after it has been written back can make some filesystems
unhappy (backing KVM guests will such filesystem files is uncommon, and
the race is minuscule, hence the lack of complaints).

See the link below for details.

Link: https://lore.kernel.org/all/cover.1683044162.git.lstoakes@gmail.com
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/loongarch/kvm/mmu.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/arch/loongarch/kvm/mmu.c b/arch/loongarch/kvm/mmu.c
index 2634a9e8d82c..364dd35e0557 100644
--- a/arch/loongarch/kvm/mmu.c
+++ b/arch/loongarch/kvm/mmu.c
@@ -608,13 +608,13 @@ static int kvm_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, bool writ
 		if (kvm_pte_young(changed))
 			kvm_set_pfn_accessed(pfn);
 
-		if (kvm_pte_dirty(changed)) {
-			mark_page_dirty(kvm, gfn);
-			kvm_set_pfn_dirty(pfn);
-		}
 		if (page)
 			put_page(page);
 	}
+
+	if (kvm_pte_dirty(changed))
+		mark_page_dirty(kvm, gfn);
+
 	return ret;
 out:
 	spin_unlock(&kvm->mmu_lock);
@@ -915,12 +915,14 @@ static int kvm_map_page(struct kvm_vcpu *vcpu, unsigned long gpa, bool write)
 	else
 		++kvm->stat.pages;
 	kvm_set_pte(ptep, new_pte);
-	spin_unlock(&kvm->mmu_lock);
 
-	if (prot_bits & _PAGE_DIRTY) {
-		mark_page_dirty_in_slot(kvm, memslot, gfn);
+	if (writeable)
 		kvm_set_pfn_dirty(pfn);
-	}
+
+	spin_unlock(&kvm->mmu_lock);
+
+	if (prot_bits & _PAGE_DIRTY)
+		mark_page_dirty_in_slot(kvm, memslot, gfn);
 
 	kvm_release_pfn_clean(pfn);
 out:
-- 
2.46.0.rc1.232.g9752f9e123-goog