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Message-ID: <ee1426d4-062d-74d5-8a9d-8bb06d554518@nvidia.com>
Date: Fri, 28 Apr 2023 11:26:59 -0700
From: John Hubbard <jhubbard@...dia.com>
To: David Hildenbrand <david@...hat.com>,
Lorenzo Stoakes <lstoakes@...il.com>
Cc: Peter Xu <peterx@...hat.com>,
"Kirill A . Shutemov" <kirill@...temov.name>,
Jason Gunthorpe <jgg@...dia.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Jens Axboe <axboe@...nel.dk>,
Matthew Wilcox <willy@...radead.org>,
Dennis Dalessandro <dennis.dalessandro@...nelisnetworks.com>,
Leon Romanovsky <leon@...nel.org>,
Christian Benvenuti <benve@...co.com>,
Nelson Escobar <neescoba@...co.com>,
Bernard Metzler <bmt@...ich.ibm.com>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Ian Rogers <irogers@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>,
Bjorn Topel <bjorn@...nel.org>,
Magnus Karlsson <magnus.karlsson@...el.com>,
Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
Jonathan Lemon <jonathan.lemon@...il.com>,
"David S . Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Christian Brauner <brauner@...nel.org>,
Richard Cochran <richardcochran@...il.com>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Jesper Dangaard Brouer <hawk@...nel.org>,
John Fastabend <john.fastabend@...il.com>,
linux-fsdevel@...r.kernel.org, linux-perf-users@...r.kernel.org,
netdev@...r.kernel.org, bpf@...r.kernel.org,
Oleg Nesterov <oleg@...hat.com>, Jan Kara <jack@...e.cz>,
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Mika Penttila <mpenttil@...hat.com>,
David Howells <dhowells@...hat.com>,
Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v5] mm/gup: disallow GUP writing to file-backed mappings
by default
On 4/28/23 10:29, David Hildenbrand wrote:
...
>> Is that an issue with interrupts disabled though? Will block page tables being
>> removed and as Kirill says (sorry I maybe misinterpreted you) we should be ok.
>
> Let's rule out page table freeing. If our VMA only spans a single page
> and falls into the same PMD as another VMA, an munmap() would not even
> free a single page table.
>
> However, if unmapping a page (flushing the TLB) would imply an IPI as
> Kirill said, we'd be fine. I recall that that's not the case for all
> architectures, but I might be just wrong.
>
Some architectures use IPIs, and others use an RCU-like approach instead.
thanks,
--
John Hubbard
NVIDIA
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