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Date: Fri, 14 Sep 2018 10:46:32 +0800 From: Lu Baolu <baolu.lu@...ux.intel.com> To: Jean-Philippe Brucker <jean-philippe.brucker@....com>, Joerg Roedel <joro@...tes.org>, David Woodhouse <dwmw2@...radead.org>, Alex Williamson <alex.williamson@...hat.com>, Kirti Wankhede <kwankhede@...dia.com> Cc: baolu.lu@...ux.intel.com, "kevin.tian@...el.com" <kevin.tian@...el.com>, "ashok.raj@...el.com" <ashok.raj@...el.com>, "tiwei.bie@...el.com" <tiwei.bie@...el.com>, "sanjay.k.kumar@...el.com" <sanjay.k.kumar@...el.com>, "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "yi.y.sun@...el.com" <yi.y.sun@...el.com>, "jacob.jun.pan@...el.com" <jacob.jun.pan@...el.com>, "kvm@...r.kernel.org" <kvm@...r.kernel.org> Subject: Re: [RFC PATCH v2 00/10] vfio/mdev: IOMMU aware mediated device Hi, On 09/13/2018 01:54 AM, Jean-Philippe Brucker wrote: > On 12/09/2018 03:42, Lu Baolu wrote: >> Hi, >> >> On 09/11/2018 12:22 AM, Jean-Philippe Brucker wrote: >>> Hi, >>> >>> On 30/08/2018 05:09, Lu Baolu wrote: >>>> Below APIs are introduced in the IOMMU glue for device drivers to use >>>> the finer granularity translation. >>>> >>>> * iommu_capable(IOMMU_CAP_AUX_DOMAIN) >>>> - Represents the ability for supporting multiple domains per device >>>> (a.k.a. finer granularity translations) of the IOMMU hardware. >>> iommu_capable() cannot represent hardware capabilities, we need >>> something else for systems with multiple IOMMUs that have different >>> caps. How about iommu_domain_get_attr on the device's domain instead? >> Domain is not a good choice for per iommu cap query. A domain might be >> attached to devices belonging to different iommu's. >> >> How about an API with device structure as parameter? A device always >> belongs to a specific iommu. This API is supposed to be used the >> device driver. > Ah right, domain attributes won't work. Your suggestion seems more > suitable, but maybe users can simply try to enable auxiliary domains > first, and conclude that the IOMMU doesn't support it if it returns an error > Some driver might want to check whether hardware supports AUX_DOMAIN during the driver probe stage, but doesn't want to enable AUX_DOMAIN at that time. One reasonable use case is driver check AUX_DOMAIN cap during driver probe and expose different sysfs nodes according to whether AUX_DOMAIN is support or not, then AUX_DOMAIN is enabled or disabled during run time through a sysfs node. With this consideration, we still need a API to check cap. How about * iommu_check_aux_domain(struct device *dev) - Check whether the iommu driver supports multiple domains on @dev. Best regards, Lu Baolu
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