From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D77E6CA9EC5 for ; Mon, 12 Oct 2026 14:46:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To: Content-Transfer-Encoding:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=kVDh4BcUbgvIW1O8+CoyCzwwqxHQNia8D9+ovujPztQ=; b=LiedSYJpZ9RkCLIv+CKW5MnV7x wnLndsTy864ReHcHZ/Z8ik17Mw8aWCewyxt+G2fb7AdiwXiLMiOikrBpMmiSu0L5D166Vdcbb/1g8 JLJ0Q0+A1P5nVRvgDU0GBpfdCzy+38plhsZSylh64igfBix1ZStQiOrfsVXx/UBR7vt903ozf/k/8 evEWKZrlvEklpcAkRUV1VhW8IVmnoPXQpkKbI8Efvf5aDpQ9V60wSMHGVNMd9qjN8Y3K+2JQO7cSZ N3L3BtME3g7R9RrFsP+xWuG6oVC248yvnoJ98Ok1C2aBuR0jl3m0ZKfphQzkMk5qvroNeXNX3wqIS DQFdzDsA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xGHIE-0000000AiZe-2Ult; Mon, 12 Oct 2026 14:46:22 +0000 Received: from mail-qt1-x833.google.com ([2607:f8b0:4864:20::833]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xGHIC-0000000AiZ5-2OQj for linux-arm-kernel@lists.infradead.org; Mon, 12 Oct 2026 14:46:21 +0000 Received: by mail-qt1-x833.google.com with SMTP id d75a77b69052e-53397554beaso21887371cf.3 for ; Mon, 12 Oct 2026 07:46:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; t=1791816378; x=1792421178; darn=lists.infradead.org; h=in-reply-to:content-transfer-encoding:content-disposition :content-type:mime-version:references:message-id:subject:cc:to:from :date:from:to:cc:subject:date:message-id:reply-to:content-type; bh=kVDh4BcUbgvIW1O8+CoyCzwwqxHQNia8D9+ovujPztQ=; b=Hh1ywStwlFD8DKY/jH59A7V16nQdOp17kojHAaB3AQgp73TDwTL556whXeC7C3vHu/ peqaBT3Tf2XIbbmfFvn99Q/9KjGBrk6fWKzdUWfylG5tAwmkctOkWDLPihztQqlvmBsP YXe3XT0Q+gy+Z6hx1vHX2MKtJzNGPK5pw/pza3s6+ZYAC842pBVWwRvbdL+AyADsWo8v s+V53NVoVgQZZdx5aFrHR+IWheOA3lMJigi7+ugpK6fB3CP3PXzSHUu7gtsBP1wBJ8ev BjYqg4qfRAEZTmysDlAZscaHmZ1YS9ssN2m0L0XK6TUYKrfg+34ioWK3WUmbFFZPUa63 y+7g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1791816378; x=1792421178; h=in-reply-to:content-transfer-encoding:content-disposition :content-type: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:content-type; bh=kVDh4BcUbgvIW1O8+CoyCzwwqxHQNia8D9+ovujPztQ=; b=tf/72E+mNVsT2QWbNA6kmLqcmC9H4euO+/GGsCCFfANvFrkZkMEs+4Jp/xao0XrSpb PSXXMWV+aKKlvnVi5FlhWe9p7hczy9Mosr3FSnJY0oa6MZZrPs+FTgcfgFTqq8mdTR7V 1zLVlXp1Qcd1QfVJTlSvd1RAWXtdIiisC7B5+J/nqQZ83bDfOuHERuDMNQK3w4Pzct2A 9JQwkQHRh/jo9fmBcuTnvUILNWH3ctCdTjw5/vxhVZ3yrsJxsO9mMQ9QGIiQ2k4EohNt pF4dTVlZviENwTFFfUcQClcbxeyzg5/PJAAjo95yvC3D2XDrvQoi8d+2Xw5vr6Nxodrh y2Yg== X-Forwarded-Encrypted: i=1; AKwUvBzzLFPqm4qY5mJxFvdVf5/BHa92Ga5jseBxFnf+L9KZJhqM2jJ4cNA87Mtub1ha6IG1xicjSDgswXsD+Scbytv9@lists.infradead.org X-Gm-Message-State: AFq9FYJMv1yFjlONy3clZvOIPpfTIljdBwwj7E8xc9r9usoasqkvgQb/ lqBJmKyIm/hgcjsj0cAP4Z52q0bX1AGecrXiuhJKuHfuLoDWHgpvsrhInLniRsKsOkw= X-Gm-Gg: AYBFou1hMOihIp9VUCTRW7Dy9epRbniAErWlhdfe7YaxR6OMItejxXkp/Qa4aFVX27F UBLHACkA3I62mal9V6fcIbi1f408caD+NCAvcp0bMwJl2L58xZQFYT6mQVrxrC1g1I/cBFaVDNS RovGhco22Z51rrrsdwNd4+082aTjE+PVXkJgUtGEcZ7U/dKIohVE3Bd7D/97BGS1W6nhLijM7b0 7DIJPPF6vpHSUgRQzABOhFLMcechZheAwjHFj/uW91neuJMRUUr4+X4Mj0gjK+0SyvGgPKxMERM 8o/2gP9V+MhT325NWTvRi/YWuBV6UeYjMfiakjvqKNNlZ77ytw06K+dE3AUQ2cGvKQWMnBAA90n l41XeuJBG0cM5vxkU4OOIbTmznts9AG+gZ1qTuI8NMT7MXAfctmi77nbht6iLwQvCbpwWFSeG4t zaPC2sMo+FLlPhnujs5yu1Buxm8LpbA3oB/fod+PCg4cCbkC4uFYrxJYP10UdHp76nBk7C8DkN6 lG7POSj62bfOkRtNWH4ndYzF1Eyj1hHhVm/KuNP9rrx6LXGX/eIBvt8 X-Received: by 2002:a05:622a:2487:b0:535:1134:91b with SMTP id d75a77b69052e-5359faead4bmr160454661cf.14.1791816378499; Mon, 12 Oct 2026 07:46:18 -0700 (PDT) Received: from ziepe.ca (hlfxns010zw-159-2-239-150.pppoe-dynamic.high-speed.ns.bellaliant.net. [159.2.239.150]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-535e652f3c7sm3157041cf.26.2026.10.12.07.46.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Oct 2026 07:46:17 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1xGHI8-00000006SW2-2nlk; Mon, 12 Oct 2026 11:46:16 -0300 Date: Mon, 12 Oct 2026 11:46:16 -0300 From: Jason Gunthorpe To: Christian =?utf-8?B?S8O2bmln?= Cc: Fred Griffoul , Paolo Bonzini , Sean Christopherson , Marc Zyngier , Oliver Upton , Sumit Semwal , Kevin Tian , David Woodhouse , Ackerley Tng , Joey Gouly , Suzuki K Poulose , Zenghui Yu , Steffen Eiden , Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H . Peter Anvin" , Joerg Roedel , Robin Murphy , Alex Williamson , Shuah Khan , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-kselftest@vger.kernel.org, linux-trace-kernel@vger.kernel.org, x86@kernel.org Subject: Re: [RFC PATCH 2/6] dma-buf: Add get_phys() to describe a physical run Message-ID: <20261012144616.GF14213@ziepe.ca> References: <20261005132046.30025-1-griffoul@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261012_074620_620124_FB427D72 X-CRM114-Status: GOOD ( 19.88 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Oct 05, 2026 at 04:53:34PM +0200, Christian König wrote: > > KVM gets its frames through the KVM-private guest_memfd provider > > interface from David's series. iommufd gets them through a private > > interface with the exporter, as it already does for vfio-pci. The new > > version adds a small registry in iommufd for that, which replaces the > > symbol_get() of the sample in David's series. The dma-buf is then only > > the handle and the existing revoke. > > Yeah that approach sounds totally sane to me. > > We have drivers which stuff all kind of resources, not just memory, > into a DMA-buf. That ranges from MMIO BARs to trigger FW operations > (doorbells) over full HW blocks (ordered appends, global wave sync > etc...) where two or more applications need to share which one is > used. > > That you then have a exporter private interface is for accessing > this is perfectly ok. > > The problem you are facing here is more that this is not limited to > one driver/module but multiple ones and you don't want module inter > dependencies because of the symbols. > > So symbol_get() is probably the right thing to do as long as we > don't have something like weak symbols or similar. I don't want to keep expanding this hack in iommufd. If dmabuf is to be used then dmabuf needs to provide a pluggable way to fill the iommu_domain that many exporters can plug into. I don't want to hardwire every exporter into iommufd, that makes no sense. The existing arrangement is to motivate solving this problem generically, not something to be expanded on. Jason