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[2003:cb:c700:2400:6b79:2aa:9602:7016]) by smtp.gmail.com with ESMTPSA id iz14-20020a05600c554e00b003f175954e71sm38857931wmb.32.2023.05.02.06.39.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 02 May 2023 06:39:52 -0700 (PDT) Message-ID: Date: Tue, 2 May 2023 15:39:50 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH v6 3/3] mm/gup: disallow FOLL_LONGTERM GUP-fast writing to file-backed mappings Content-Language: en-US To: Jason Gunthorpe Cc: Christian Borntraeger , Lorenzo Stoakes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Jens Axboe , Matthew Wilcox , Dennis Dalessandro , Leon Romanovsky , Christian Benvenuti , Nelson Escobar , Bernard Metzler , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Ian Rogers , Adrian Hunter , Bjorn Topel , Magnus Karlsson , Maciej Fijalkowski , Jonathan Lemon , "David S . 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Shutemov" , Pavel Begunkov , Mika Penttila , Dave Chinner , Theodore Ts'o , Peter Xu , Matthew Rosato References: <7d56b424-ba79-4b21-b02c-c89705533852@lucifer.local> From: David Hildenbrand Organization: Red Hat In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-perf-users@vger.kernel.org On 02.05.23 15:36, Jason Gunthorpe wrote: > On Tue, May 02, 2023 at 03:28:40PM +0200, David Hildenbrand wrote: >> On 02.05.23 15:10, Jason Gunthorpe wrote: >>> On Tue, May 02, 2023 at 03:04:27PM +0200, Christian Borntraeger wrote: >>> \> > We can reintroduce a flag to permit exceptions if this is really broken, are you >>>>> able to test? I don't have an s390 sat around :) >>>> >>>> Matt (Rosato on cc) probably can. In the end, it would mean having >>>> >>>> >>>> >>> >>> This s390 code is the least of the problems, after this series VFIO >>> won't startup at all with this configuration. >> >> Good question if the domain would fail to start. I recall that IOMMUs for >> zPCI are special on s390x. [1] > > Not upstream they aren't. > >> Well, zPCI is special. I cannot immediately tell when we would trigger >> long-term pinning. > > zPCI uses the standard IOMMU stuff, so it uses a normal VFIO container > and the normal pin_user_pages() path. @Christian, Matthew: would we pin all guest memory when starting the domain (IIRC, like on x86-64) and fail early, or only when the guest issues rpcit instructions to map individual pages? -- Thanks, David / dhildenb