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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 40EF2C3815B for ; Mon, 20 Apr 2020 11:55:14 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 1597921744 for ; Mon, 20 Apr 2020 11:55:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="hIOk6l6o" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1597921744 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject: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=nln1kOIf1CUIEK2qFPniOkifJaaBFDBcvremwFqBuMs=; b=hIOk6l6ozJw6ob dk38X6slD0YaKyQ50kQkXSnVeF9THNN190Cn5YQZCpzRz2kc/tVHR/XpuL+ZNI6kca8rENelse10h IdtvzT2C7Pe/FBMKVjE25J9NIO6HXipSsWBWzUZjj9IRXABPl+if18H1Pzq3M/AFyDm5c2p9ahDKL nOjGHNy3PlV/wR1+mPR2DrOBXyPDTfByqtNVbcGKVDpVgXxUuV0YjT0w6RoNYVl9Ewcp8lr62K5GW G1WEfyiRakAYK2dApAVasCvRNnP61G92STV2Sa8KG8iyppo3+ABznH0SLEqnHoC2PjlOw7ZcvXnmw xcgODg4JO4Dae5SVz7kA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jQV13-0007hw-W3; Mon, 20 Apr 2020 11:55:09 +0000 Received: from hch by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jQV0y-0006P9-DC; Mon, 20 Apr 2020 11:55:04 +0000 Date: Mon, 20 Apr 2020 04:55:04 -0700 From: Christoph Hellwig To: Christian =?iso-8859-1?Q?K=F6nig?= Subject: Re: [PATCH v5 02/25] iommu/sva: Manage process address spaces Message-ID: <20200420115504.GA20664@infradead.org> References: <20200414170252.714402-1-jean-philippe@linaro.org> <20200414170252.714402-3-jean-philippe@linaro.org> <20200416072852.GA32000@infradead.org> <20200416085402.GB1286150@myrica> <20200416121331.GA18661@infradead.org> <20200420074213.GA3180232@myrica> <20200420081034.GA17305@infradead.org> <6b195512-fa73-9a49-03d8-1ed92e86f607@amd.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <6b195512-fa73-9a49-03d8-1ed92e86f607@amd.com> X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jean-Philippe Brucker , kevin.tian@intel.com, jacob.jun.pan@linux.intel.com, devicetree@vger.kernel.org, jgg@ziepe.ca, linux-pci@vger.kernel.org, joro@8bytes.org, Jonathan.Cameron@huawei.com, robin.murphy@arm.com, Christoph Hellwig , linux-mm@kvack.org, iommu@lists.linux-foundation.org, catalin.marinas@arm.com, zhangfei.gao@linaro.org, will@kernel.org, xuzaibo@huawei.com, linux-arm-kernel@lists.infradead.org, baolu.lu@linux.intel.com Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Apr 20, 2020 at 01:44:56PM +0200, Christian K=F6nig wrote: > Am 20.04.20 um 10:10 schrieb Christoph Hellwig: > > On Mon, Apr 20, 2020 at 09:42:13AM +0200, Jean-Philippe Brucker wrote: > > > Right, I can see the appeal. I still like having a single mmu notifie= r per > > > mm because it ensures we allocate a single PASID per mm (as required = by > > > x86). I suppose one alternative is to maintain a hashtable of mm->pas= id, > > > to avoid iterating over all bonds during allocation. > > Given that the PASID is a pretty generic and important concept can > > we just add it directly to the mm_struct and allocate it lazily once > > we first need it? > = > Well the problem is that the PASID might as well be device specific. E.g. > some devices use 16bit PASIDs, some 15bit, some other only 12bit. > = > So what could (at least in theory) happen is that you need to allocate > different PASIDs for the same process because different devices need one. This directly contradicts the statement from Jean-Philippe above that x86 requires a single PASID per mm_struct. If we may need different PASIDs for different devices and can actually support this just allocating one per [device, mm_struct] would make most sense of me, as it doesn't couple otherwise disjoint state. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel