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charset="us-ascii" X-Rspamd-Queue-Id: F0D1314002C X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: ew9iquy5xfzhasre16ej8d1um15dzymr X-HE-Tag: 1709579092-738214 X-HE-Meta: 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 hMQiy+zQ 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.027284, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Mar 04, 2024, Quentin Perret wrote: > > As discussed in the sub-thread, that might still be required. > > > > One could think about completely forbidding GUP on these mmap'ed > > guest-memfds. But likely, there might be use cases in the future where you > > want to use GUP on shared memory inside a guest_memfd. > > > > (the iouring example I gave might currently not work because > > FOLL_PIN|FOLL_LONGTERM|FOLL_WRITE only works on shmem+hugetlb, and > > guest_memfd will likely not be detected as shmem; 8ac268436e6d contains some > > details) > > Perhaps it would be wise to start with GUP being forbidden if the > current users do not need it (not sure if that is the case in Android, > I'll check) ? We can always relax this constraint later when/if the > use-cases arise, which is obviously much harder to do the other way > around. +1000. At least on the KVM side, I would like to be as conservative as possible when it comes to letting anything other than the guest access guest_memfd.