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[47.54.130.67]) by smtp.gmail.com with ESMTPSA id af79cd13be357-920a133621bsm235489985a.11.2026.06.19.06.16.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Jun 2026 06:16:59 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1waZ5e-00000004YKj-2eO9; Fri, 19 Jun 2026 10:16:58 -0300 Date: Fri, 19 Jun 2026 10:16:58 -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: <20260619131658.GA1068655@ziepe.ca> References: <20260616180129.160016-1-anthony.pighin@nokia.com> <20260616163054.77fdb61a@shazbot.org> <20260617192928.GB231643@ziepe.ca> <20260618153049.GG231643@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: CF279A000E X-Stat-Signature: 9ejzrom9x9agsetgpmpomyq4tux7afdd X-HE-Tag: 1781875020-950391 X-HE-Meta: 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 UDQveGPw Q2XAGjsmgElLV3zwOwki/9b/uw2v71aV6lhUFk2FGCSE545dyD+2zgCMrWSZM8oYNbudtlZdsIV0+tcCV9/lnicO5+MpKr7oD3VoY6rLg7csvRvUXkPmSyZ91UlCg6KRp5pkGi1IkaEObyLZnxf7nY3n6VAetzkoNASZExywXgiXVpqM8cSEgwGpZ5QJoPUMrMrd+tg1pj1VWlnRQH3znl39X0BfXEYJ6TDobDi/14D1Rhc/gyAUZ22kHEmA25LjlR3OmieD6eaCG3oF2LsOV2JlRvoIDA+d41rjxzsgbFIjzLqUDI/Apcns36i+cFWRwJBZf/2x9oc5ROGxjsN/GU2GUG4DTu7YY/QA/hxQ7K/3xxI9USTbh0cOzEg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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? Jason