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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id 143sm21181798wmb.47.2021.02.08.08.47.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 08 Feb 2021 08:47:23 -0800 (PST) Subject: Re: [PATCH v2] KVM: x86/MMU: Do not check unsync status for root SP. To: Yu Zhang Cc: seanjc@google.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, vkuznets@redhat.com, wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org References: <20210207122254.23056-1-yu.c.zhang@linux.intel.com> <671ae214-22b9-1d89-75cb-0c6da5230988@redhat.com> <20210208134923.smtvzeonvwxzdlwn@linux.intel.com> From: Paolo Bonzini Message-ID: <404bce5c-19ef-e103-7b68-5c81697d2a1f@redhat.com> Date: Mon, 8 Feb 2021 17:47:22 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20210208134923.smtvzeonvwxzdlwn@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/02/21 14:49, Yu Zhang wrote: > On Mon, Feb 08, 2021 at 12:36:57PM +0100, Paolo Bonzini wrote: >> On 07/02/21 13:22, Yu Zhang wrote: >>> In shadow page table, only leaf SPs may be marked as unsync. >>> And for non-leaf SPs, we use unsync_children to keep the number >>> of the unsynced children. In kvm_mmu_sync_root(), sp->unsync >>> shall always be zero for the root SP, , hence no need to check >>> it. Instead, a warning inside mmu_sync_children() is added, in >>> case someone incorrectly used it. >>> >>> Also, clarify the mmu_need_write_protect(), by moving the warning >>> into kvm_unsync_page(). >>> >>> Signed-off-by: Yu Zhang >>> Signed-off-by: Sean Christopherson >> >> This should really be more of a Co-developed-by, and there are a couple >> adjustments that could be made in the commit message. I've queued the patch >> and I'll fix it up later. > > Indeed. Thanks for the remind, and I'll pay attention in the future. :) Also: arch/x86/kvm/mmu/mmu.c: In function ‘mmu_sync_children’: arch/x86/kvm/mmu/mmu.c:2002:17: error: ‘sp’ is used uninitialized in this function [-Werror=uninitialized] WARN_ON_ONCE(sp->unsync); so how was this tested? Paolo