From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 23053B6F62 for ; Tue, 23 Aug 2011 06:54:07 +1000 (EST) Subject: Re: kvm PCI assignment & VFIO ramblings From: Benjamin Herrenschmidt To: Avi Kivity In-Reply-To: <4E51F782.7060005@redhat.com> References: <1311983933.8793.42.camel@pasglop> <1312050011.2265.185.camel@x201.home> <20110802082848.GD29719@yookeroo.fritz.box> <1312308847.2653.467.camel@bling.home> <1312310121.2653.470.camel@bling.home> <20110803020422.GF29719@yookeroo.fritz.box> <4E3F9E33.5000706@redhat.com> <1312932258.4524.55.camel@bling.home> <1312944513.29273.28.camel@pasglop> <1313859105.6866.192.camel@x201.home> <4E51F782.7060005@redhat.com> Content-Type: text/plain; charset="UTF-8" Date: Tue, 23 Aug 2011 06:53:46 +1000 Message-ID: <1314046426.7662.30.camel@pasglop> Mime-Version: 1.0 Cc: chrisw , Alexey Kardashevskiy , kvm@vger.kernel.org, Paul Mackerras , "linux-pci@vger.kernel.org" , qemu-devel , iommu , aafabbri , Alex Williamson , Anthony Liguori , linuxppc-dev , benve@cisco.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, 2011-08-22 at 09:30 +0300, Avi Kivity wrote: > On 08/20/2011 07:51 PM, Alex Williamson wrote: > > We need to address both the description and enforcement of device > > groups. Groups are formed any time the iommu does not have resolution > > between a set of devices. On x86, this typically happens when a > > PCI-to-PCI bridge exists between the set of devices and the iommu. For > > Power, partitionable endpoints define a group. Grouping information > > needs to be exposed for both userspace and kernel internal usage. This > > will be a sysfs attribute setup by the iommu drivers. Perhaps: > > > > # cat /sys/devices/pci0000:00/0000:00:19.0/iommu_group > > 42 > > > > $ readlink /sys/devices/pci0000:00/0000:00:19.0/iommu_group > ../../../path/to/device/which/represents/the/resource/constraint > > (the pci-to-pci bridge on x86, or whatever node represents partitionable > endpoints on power) The constraint might not necessarily be a device. The PCI bridge is just an example. There are other possible constraints. On POWER for example, it could be a limit in how far I can segment the DMA address space, forcing me to arbitrarily put devices together, or it could be a similar constraint related to how the MMIO space is broken up. So either that remains a path in which case we do have a separate set of sysfs nodes representing the groups themselves which may or may not itself contain a pointer to the "constraining" device, or we just make that an arbitrary number (in my case the PE#) Cheers, Ben