> From: Lu Baolu [mailto:baolu.lu@xxxxxxxxxxxxxxx] > Sent: Friday, September 14, 2018 10:47 AM > > 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. > maybe generalized as iommu_check_attr with aux_domain as a flag, in case other IOMMU checks introduced in the future. hinted by Jean's comment on iommu_sva_device_init part. Thanks Kevin
