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[91.12.100.159]) by smtp.gmail.com with ESMTPSA id d15sm12268494edu.86.2021.05.03.01.11.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 03 May 2021 01:11:30 -0700 (PDT) Subject: Re: [PATCH v1 5/7] mm: introduce page_offline_(begin|end|freeze|unfreeze) to synchronize setting PageOffline() To: Mike Rapoport Cc: linux-kernel@vger.kernel.org, Andrew Morton , "Michael S. Tsirkin" , Jason Wang , Alexey Dobriyan , "Matthew Wilcox (Oracle)" , Oscar Salvador , Michal Hocko , Roman Gushchin , Alex Shi , Steven Price , Mike Kravetz , Aili Yao , Jiri Bohac , "K. Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , Wei Liu , Naoya Horiguchi , linux-hyperv@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org References: <20210429122519.15183-1-david@redhat.com> <20210429122519.15183-6-david@redhat.com> From: David Hildenbrand Organization: Red Hat Message-ID: <4aa55978-c224-7ead-f00d-df1a6c3dfda4@redhat.com> Date: Mon, 3 May 2021 10:11:29 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org On 02.05.21 08:33, Mike Rapoport wrote: > On Thu, Apr 29, 2021 at 02:25:17PM +0200, David Hildenbrand wrote: >> A driver might set a page logically offline -- PageOffline() -- and >> turn the page inaccessible in the hypervisor; after that, access to page >> content can be fatal. One example is virtio-mem; while unplugged memory >> -- marked as PageOffline() can currently be read in the hypervisor, this >> will no longer be the case in the future; for example, when having >> a virtio-mem device backed by huge pages in the hypervisor. >> >> Some special PFN walkers -- i.e., /proc/kcore -- read content of random >> pages after checking PageOffline(); however, these PFN walkers can race >> with drivers that set PageOffline(). >> >> Let's introduce page_offline_(begin|end|freeze|unfreeze) for > > Bikeshed: freeze|thaw? > Sure :) -- Thanks, David / dhildenb