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From: Oliver Upton To: Sean Christopherson Cc: Paolo Bonzini , Marc Zyngier , Tianrui Zhao , Bibo Mao , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, David Matlack , David Stevens , Fuad Tabba Subject: Re: [PATCH v12 54/84] KVM: arm64: Mark "struct page" pfns accessed/dirty before dropping mmu_lock Message-ID: References: <20240726235234.228822-1-seanjc@google.com> <20240726235234.228822-55-seanjc@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240805_165629_194676_694A3068 X-CRM114-Status: GOOD ( 18.48 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Aug 05, 2024 at 04:53:01PM -0700, Sean Christopherson wrote: > On Mon, Aug 05, 2024, Oliver Upton wrote: > > > > --- > > > > arch/arm64/kvm/mmu.c | 10 ++++++---- > > > > 1 file changed, 6 insertions(+), 4 deletions(-) > > > > > > > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > > > > index 22ee37360c4e..ce13c3d884d5 100644 > > > > --- a/arch/arm64/kvm/mmu.c > > > > +++ b/arch/arm64/kvm/mmu.c > > > > @@ -1685,15 +1685,17 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > > > > } > > > > > > > > out_unlock: > > > > + if (writable && !ret) > > > > + kvm_set_pfn_dirty(pfn); > > > > > > I'm guessing you meant kvm_release_pfn_dirty() here, because this leaks > > > a reference. > > Doh, I did indeed. Alternatively, this could be: > > if (writable && !ret) > kvm_set_pfn_dirty(pfn); > > kvm_release_pfn_clean(pfn); > > It won't matter in the end, because this just becomes: > > kvm_release_faultin_page(kvm, page, !!ret, writable); > > So I guess the question is if you prefer to make the switch to an if-else in this > path, or more implicitly in the conversion to kvm_release_faultin_page(). > > I made the same goof for RISC-V, perhaps to prove that I too can copy+paste arm64's > MMU code ;-) LOL, whatever way you want to address it is fine by me, just wanted to make sure this intermediate bug wouldn't bite an unlucky bisection. -- Thanks, Oliver