From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Mon, 21 Nov 2011 15:35:05 -0800 From: Chris Wright To: Joerg Roedel Cc: Alex Williamson , iommu@lists.linux-foundation.org, dwmw2@infradead.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org Subject: Re: [PATCH] iommu: Include MSI susceptibility to DMA in creating iommu groups Message-ID: <20111121233505.GG3344@sequoia.sous-sol.org> References: <20111117170800.3125.84150.stgit@bling.home> <20111118104651.GJ5627@amd.com> <1321628190.26410.63.camel@bling.home> <20111118152710.GA5098@amd.com> <1321633956.26410.126.camel@bling.home> <20111120120043.GB20535@8bytes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20111120120043.GB20535@8bytes.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: * Joerg Roedel (joro@8bytes.org) wrote: > >From device standpoint a MSI transaction is always a DMA memory write > to a given address range. The IOMMU-API should export a feature flag > whether it supports filtering on those transaction or not. We have that > today with the IOMMU_CAP_INTR_REMAP. I agree that the interface to get > this information is ugly because a domain is needed. But the interface > can be fixed. While doing this I suggest to rename that feature > IOMMU_CAP_INTR_ISOLATION or something like that. > VFIO can then check for this flag on module-load and refuse to load if > it is not available. I can see that the native grouping (the typical pci bridge type) is really more a property of the topology. The isolation properties of a group (arguably the whole point of the group) is subtly different. Leaves the questions: What is the value of a group w/out complete isolation? Is there a practical problem w/ conflating the subtleties above? thanks, -chris