From: Jason Gunthorpe <jgg@ziepe.ca>
To: Lorenzo Stoakes <ljs@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>,
Peter Xu <peterx@redhat.com>, Alex Williamson <alex@shazbot.org>,
Anthony Pighin <anthony.pighin@nokia.com>,
linux-kernel@vger.kernel.org,
Kefeng Wang <wangkefeng.wang@huawei.com>,
kvm@vger.kernel.org, linux-mm@kvack.org,
"Liam R. Howlett" <liam@infradead.org>,
Ryan Roberts <ryan.roberts@arm.com>
Subject: Re: [PATCH] vfio: Request THP-aligned mmap for device fds
Date: Fri, 19 Jun 2026 10:16:58 -0300 [thread overview]
Message-ID: <20260619131658.GA1068655@ziepe.ca> (raw)
In-Reply-To: <ajQRY7tHShCEz8vg@lucifer>
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
next prev parent reply other threads:[~2026-06-19 13:17 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20260616180129.160016-1-anthony.pighin@nokia.com>
[not found] ` <20260616163054.77fdb61a@shazbot.org>
[not found] ` <ajKtdCN0AlbmBnAj@x1.local>
2026-06-17 18:34 ` [PATCH] vfio: Request THP-aligned mmap for device fds Matthew Wilcox
2026-06-17 19:29 ` Jason Gunthorpe
2026-06-18 14:55 ` Lorenzo Stoakes
2026-06-18 15:04 ` Matthew Wilcox
2026-06-18 15:30 ` Jason Gunthorpe
2026-06-18 15:56 ` Lorenzo Stoakes
2026-06-19 13:16 ` Jason Gunthorpe [this message]
2026-06-18 15:28 ` Jason Gunthorpe
2026-06-19 16:11 ` Matthew Wilcox
2026-06-19 17:07 ` Jason Gunthorpe
2026-06-19 15:04 ` Ryan Roberts
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