From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qv1-f47.google.com (mail-qv1-f47.google.com [209.85.219.47]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BB07A2571A0 for ; Mon, 26 Jan 2026 21:01:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.47 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769461273; cv=none; b=qWUPSlNi+nH1tpIQ4KhfTbtzwlbjLk3IVZnBvyC+F4RepTdNRmtgbnWDM3x2j1NGuKGh4+kzCOxTSEqaxeJ5oeCbJ5ammNpKmnpCrvQb0fq0+269u7VNumIaxx78HfFqotBbMxEbl6IOEaVKrkD2H+90qWx+YeOrLy9xYurxvlI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769461273; c=relaxed/simple; bh=/uBBJ41PsJ+poHfkbr45RI19WGdtV1Pwu8dAjRjrE+U=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=MPn2q2yFXD2urHYCmKUOaQFrf1Wzuz8RGUhoSGA5hqXk7lOvFFaWnJlN2pxOV3L9rEDJqeoTYt4LZDvj2q1A3N41/tvKkrMFH1bd2zoneiGkbGHecnpSEqMCUMv7xGHfDccNow/TGHZNToA71B9f9vIk6C91v9r7Jfb4WZeHLxU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ziepe.ca; spf=pass smtp.mailfrom=ziepe.ca; dkim=pass (2048-bit key) header.d=ziepe.ca header.i=@ziepe.ca header.b=koC1Q+iD; arc=none smtp.client-ip=209.85.219.47 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ziepe.ca Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ziepe.ca Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=ziepe.ca header.i=@ziepe.ca header.b="koC1Q+iD" Received: by mail-qv1-f47.google.com with SMTP id 6a1803df08f44-89461ccc46eso89763036d6.2 for ; Mon, 26 Jan 2026 13:01:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; t=1769461270; x=1770066070; darn=lists.linux.dev; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=Tu3uAyHuSXXXZq6VSWtVG72sHh/RWKg7/MHSYDvcONg=; b=koC1Q+iDSahvWalXWFQLqhD1axRaLPr54xKPCYIW6In+rWyfE+fmE4zDEmWU6SLpGB BTQgqfTAQqhqqsG3RP/V9Bky9yMXYew8pqyPUEGwVdGAj9r6BJr3v0t3J7j9UOc2+gP6 hU88ZX+aWt4ixBDx283qV0ApdkCzihfQasRec2v1GuLcA7pb/aeCrmyIK4ax9NGgw3eG 2wa1rB9NjS15udWFWQXwfGWfpr7q1a3vOHHUQdfoDZdJ/s1haOFXuejy3FL3NWr56x3r NOo4Yyg1TvgKwdrWN2YFU95Aw11BOR4DPkuMODJHsvAVhforRRtVgwEZvpXhtX69Whbf waOQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1769461270; x=1770066070; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=Tu3uAyHuSXXXZq6VSWtVG72sHh/RWKg7/MHSYDvcONg=; b=kwNkZa+I63Iaa7ZRuaWgxrGyGWqOyBYTbm1OpMbenYIJD+kPocsfogmA6WLZSO13+W cX7b1aEUjo7lCrLjh5NUpl9sdku8f8HwUGC7IrUNN7/nX0h4xybYjLb7Gd4rfY8h/0RE aqhhrSQmturdEz5A+xF5lw+HhqT8P9it142CgEVcsa1mWL9EQ4kn9GLg1hv35munlbFR hNhlqcXH/OydKCdTDb+R1MoeGDV5kdLp+zb+LFdLchDaz6KEgJcbUtEOIh+7W7ARSWkF vp25gS2miIRtmZ5TKG/OGdMgXxQeFP/11R7fwoHOTSgajrm6Ytk0n68ugTi83Xyub9aq /MmA== X-Forwarded-Encrypted: i=1; AJvYcCU1XQdTJ8dqlvrkswRkTouuDJYfKIgVtteucizGyaVXC/6/ZoMU3gumv0RvuGFd0E5dssIIQQ==@lists.linux.dev X-Gm-Message-State: AOJu0YwR0199Tf1IoGtbDkAeYWPjLMLXyGjTPWP/G6belnAPd0gdVl1m puBoodeW3AdkDW6SkFYUlacFjdOT7X7zhdqaAM/R4p9Xw2KFlsDFbrW6GlDfzUqb5L0= X-Gm-Gg: AZuq6aIXLjz4kg8aXcHoRadeu1ZgWjiJ4G4zOnuO2fuRZTMB4tyF6OmqMwwXNg1HluH SsBm4QQAsFIfVOXimwTFHMK0OsGEkVwmEPeJgBUy0Dff2cMeXSaKYs7Va/Stjg03Hgz3zqECW7S f8NXmHKBFOa+Ugsnr3KXnT5E1D5aE5E+yiWAgsLIsfGmeeulhx/D3XJTDINTLGSzMWroM5EbEyr aGizULN0wvXAhUTq3BbEeQ/m4hlvsGGBp1u29mYqFCeYA6rUhg+BdACiASyENOg0hs3lUBvVBWE 2Jh/HVqa3WrqiRsV6gKe8cV/28bhiB/mHgNfPq4X5fYzojuEqLCw0YsNHC7Mr8kVqITXg8jB5sv UQ8eOMZ1wLe/q95hwiFAalGo7lfHyglvFMPz5UGLfd5Mb8yflAqIbyZwGeDefWkG6ah1B0BFk2Y QU7z2Vwk3hOMOBVy6V1MOtRW8Cfoiw+yzNsHCRQpcZgclQYTEMN/b1nk40eGBnk8wvvpA= X-Received: by 2002:a05:6214:1cc9:b0:894:7b34:dacd with SMTP id 6a1803df08f44-894b06f336dmr73487126d6.31.1769461270245; Mon, 26 Jan 2026 13:01:10 -0800 (PST) Received: from ziepe.ca (hlfxns017vw-142-162-112-119.dhcp-dynamic.fibreop.ns.bellaliant.net. [142.162.112.119]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-894918b1436sm104983856d6.35.2026.01.26.13.01.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Jan 2026 13:01:09 -0800 (PST) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1vkThs-00000008z30-31vX; Mon, 26 Jan 2026 17:01:08 -0400 Date: Mon, 26 Jan 2026 17:01:08 -0400 From: Jason Gunthorpe To: Pranjal Shrivastava Cc: Leon Romanovsky , Sumit Semwal , Christian =?utf-8?B?S8O2bmln?= , Alex Deucher , David Airlie , Simona Vetter , Gerd Hoffmann , Dmitry Osipenko , Gurchetan Singh , Chia-I Wu , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Lucas De Marchi , Thomas =?utf-8?Q?Hellstr=C3=B6m?= , Rodrigo Vivi , Kevin Tian , Joerg Roedel , Will Deacon , Robin Murphy , Felix Kuehling , Alex Williamson , Ankit Agrawal , Vivek Kasireddy , linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, virtualization@lists.linux.dev, intel-xe@lists.freedesktop.org, linux-rdma@vger.kernel.org, iommu@lists.linux.dev, kvm@vger.kernel.org Subject: Re: [PATCH v5 6/8] dma-buf: Add dma_buf_attach_revocable() Message-ID: <20260126210108.GD1641016@ziepe.ca> References: <20260124-dmabuf-revoke-v5-0-f98fca917e96@nvidia.com> <20260124-dmabuf-revoke-v5-6-f98fca917e96@nvidia.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Jan 26, 2026 at 08:38:44PM +0000, Pranjal Shrivastava wrote: > I noticed that Patch 5 removes the invalidate_mappings stub from > umem_dmabuf.c, effectively making the callback NULL for an RDMA > importer. Consequently, dma_buf_attach_revocable() (introduced here) > will return false for these importers. Yes, that is the intention. > Since the cover letter mentions that VFIO will use > dma_buf_attach_revocable() to prevent unbounded waits, this appears to > effectively block paths like the VFIO-export -> RDMA-import path.. It remains usable with the ODP path and people are using that right now. > Given that RDMA is a significant consumer of dma-bufs, are there plans > to implement proper revocation support in the IB/RDMA core (umem_dmabuf)? This depends on each HW, they need a way to implement the revoke semantic. I can't guess what is possible, but I would hope that most HW could at least do a revoke on a real MR. Eg a MR rereg operation to a kernel owned empty PD is an effective "revoke", and MR rereg is at least defined by standards so HW should implement it. > It would be good to know if there's a plan for bringing such importers > into compliance with the new revocation semantics so they can interop > with VFIO OR are we completely ruling out users like RDMA / IB importing > any DMABUFs exported by VFIO? It will be driver dependent, there is no one shot update here. Jason