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[47.54.130.67]) by smtp.gmail.com with ESMTPSA id af79cd13be357-92e622eb9d2sm233423485a.29.2026.06.30.05.46.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Jun 2026 05:46:30 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1weXrB-00000001r2J-2EhA; Tue, 30 Jun 2026 09:46:29 -0300 Date: Tue, 30 Jun 2026 09:46:29 -0300 From: Jason Gunthorpe To: Lorenzo Stoakes Cc: Matthew Wilcox , Peter Xu , Alex Williamson , Anthony Pighin , linux-kernel@vger.kernel.org, Kefeng Wang , kvm@vger.kernel.org, linux-mm@kvack.org, "Liam R. Howlett" , Ryan Roberts Subject: Re: [PATCH] vfio: Request THP-aligned mmap for device fds Message-ID: <20260630124629.GE7525@ziepe.ca> References: <20260616163054.77fdb61a@shazbot.org> <20260617192928.GB231643@ziepe.ca> <20260618153049.GG231643@ziepe.ca> <20260619131658.GA1068655@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: AA92F40004 X-Rspam-User: X-Stat-Signature: koxs9ed5zztf4ti8if4fhz1451jm7f59 X-HE-Tag: 1782823591-886447 X-HE-Meta: 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 0J5mnCl7 zSKClgPx0Cc8r2p4XsTQRZxPm+2jqeFWwrvyC0bMS62zYqZVcFpejA/zbNLwzQlmEwHQtO4QwJBjTD8j9S24WgPn8j4ttYGocwMKcqRV6DoIPzzmBr4RL2o1WcmAYc4CV5X1lrilV+4PvVHhPHi8MzgwRxenITICfBeveFb2QgGgn5E5iua17DLzI8GCz5tB1ZnAhMv1CE3zsNlxL4e41FSzhoGzvIO0c7Ly0NQb0wJHw3/Am1hpcaVpGDK2xfKqZ8fpBAOdepmbqmINyFrd13nCUYsQ95SyH0CBrUZ113qPvoaDGoi+yf3hN6ACJo8xP6uadueybThCgYCZ23bYWRlXK6kcLg7cD9SjPRqPUU8NaZPxUqOeX+T1PTg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Jun 22, 2026 at 05:54:10PM +0100, Lorenzo Stoakes wrote: > On Fri, Jun 19, 2026 at 10:16:58AM -0300, Jason Gunthorpe wrote: > > On Thu, Jun 18, 2026 at 04:56:06PM +0100, Lorenzo Stoakes wrote: > > > > > What you're saying is that offset 0 of the opened file might correspond > > > > > to a PFN that is not aligned in any way? I had assumed that when trying > > > > > to do the mapping of (2MB+4KiB to 64MB), that the offset specified to > > > > > mmap was 2MB+4KiB. But you seem to be saying that the offset in that > > > > > case would be 0 and someone needs to know that it corresponds to a PFN > > > > > that is misaligned? > > > > > > > > I do expect that the pgoff space is usually aligned to the pfn space, > > > > most drivers do that or could be improved to do that. There will be > > > > some off cases, but maybe we don't care, and VFIO should be fine. > > > > > > Some stuff has weird assumptions about pfn=0 at start of the range (DMA for > > > instance). > > > > Do you have a pointer? I'm drawing a blank what "dma" is? > > (I am obliged to link https://xkcd.com/138/... :) > > dmabuf as in [0], where vma->vm_pgoff must be the page offset > into the DMA buffer. > > [0]:https://elixir.bootlin.com/linux/v7.1/source/kernel/dma/direct.c#L550 That's not "dmabuf" that is the DMA API's dma_mmap() interface, very different thing. This could probably be reworked if it is some issue.. Jason