From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BD661243367; Sat, 11 Jul 2026 08:38:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783759094; cv=none; b=N0/FggPgM0/zGpVfgeorqpNwujT/k/6XvHmSIasdEdPcxvF1KkzYxTFLU8jyTi1AR5XxiXAAF6CXYm2581moZSZq0rDcQsiAyucTLcFGXEHUT0dW3qVxTgDbYaXyZDu9A/YvpcA5pjrwht6d37R19Bh3rvoDQZt8b068fkeGiJY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783759094; c=relaxed/simple; bh=CyRaJPcTWVJNhdmwT9EN24t6ISjiq/A84da/xrY/4Vo=; h=MIME-Version:Content-Type:Subject:From:To:Cc:In-Reply-To: References:Date:Message-Id; b=i7CCwY3+rSh4pAOA76A6hr/3FexAFmJBo+gsiDAGP7fCfhT/LKMePt9VGWHeKgJ1bIgmC0+tVYSBGnku+fdEYcl/vSUmnnSHjZ4TbBj8wzXXwMcSi2hC2fgfD/ByCI//MHkEmNvzK7nEluRlYoAujz30Zu+T2gzO2nmVFk3vZTI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BY+Mmh8/; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BY+Mmh8/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 667921F000E9; Sat, 11 Jul 2026 08:38:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783759093; bh=BzbbZ75tk0Gn1LrlFpT1UxEwPwXypDF6thZXD0DNZlY=; h=Subject:From:To:Cc:In-Reply-To:References:Date; b=BY+Mmh8/jRilUEL9EUyh64uk3XDuqoCgdDxAwxDMiucPAy+8WcCaH9Ro1jHnLGy01 gCkb5GbNgGWXVZnZkM5gZlt/9X2jol+Gy40MZGt0bmxkNEDwYrXeUTPJdgVTtO5ZVt WK5gNNgBBUbW4ZOLGJCBWVON0cholPeLMi4pXA11dGIvzsTCH3D7jioxJIhvgVPsKH O/N5qUHiKNciqobi+VvsWkvXEfJXdwf9ExS/NaFZKsc7r/i6rmWFiGumfqyqM7Am4a H6kjsfC8N42inUSM811TIZoIVSSTFL2tj/aeVHSNAw7QeG91L8mozBqJGsWv7twIhc gIu7PK9tQco7A== Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Subject: Re: [PATCH] vfio: Request THP-aligned mmap for device fds From: Lorenzo Stoakes To: Jason Gunthorpe Cc: Lorenzo Stoakes , 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 In-Reply-To: <20260630124629.GE7525@ziepe.ca> References: <20260616163054.77fdb61a@shazbot.org> <20260617192928.GB231643@ziepe.ca> <20260618153049.GG231643@ziepe.ca> <20260619131658.GA1068655@ziepe.ca> <20260630124629.GE7525@ziepe.ca> Date: Sat, 11 Jul 2026 09:37:59 +0100 Message-Id: <178375907930.146648.4528264473005431141.b4-reply@b4> X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=1766; i=ljs@kernel.org; h=from:subject:message-id; bh=CyRaJPcTWVJNhdmwT9EN24t6ISjiq/A84da/xrY/4Vo=; b=kA0DAAoWz53NioHifxQByyZiAGpSAOiiJdkLwOBNYMQ01kLLPZdUye72/Ik5n7i90gLpnzNQ5 Ih1BAAWCgAdFiEE5/QXv1IUVp6J0E9Gz53NioHifxQFAmpSAOgACgkQz53NioHifxTT3gD/Zw3+ WKEGhLawmfopUhw+JxYey8s/tP1cc7qS8Hwo83YBAM2u9V8WmkkvOpEFTVv/K3q4Vb7NxE+pRuG uZp1xjdwG X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 On 2026-06-30 09:46 -0300, Jason Gunthorpe wrote: > 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.. Yeah right that's what I mean. And I plan to do some rework around that as part of mmap_prepare() I have some slightly bitrotting patches for this that I'll shake down at some point... > > Jason > Cheers, Lorenzo