Re: [libvirt] [Qemu-devel] [PATCH v7 0/4] Add Mediated device support

On Wed, 7 Sep 2016 23:36:28 +0530 Kirti Wankhede <kwankhede(a)nvidia.com&gt; wrote: > On 9/7/2016 10:14 PM, Alex Williamson wrote: >> On Wed, 7 Sep 2016 21:45:31 +0530 >> Kirti Wankhede <kwankhede(a)nvidia.com&gt; wrote: >> >>> On 9/7/2016 2:58 AM, Alex Williamson wrote: >>>> On Wed, 7 Sep 2016 01:05:11 +0530 >>>> Kirti Wankhede <kwankhede(a)nvidia.com&gt; wrote: >>>> >>>>> On 9/6/2016 11:10 PM, Alex Williamson wrote: >>>>>> On Sat, 3 Sep 2016 22:04:56 +0530 >>>>>> Kirti Wankhede <kwankhede(a)nvidia.com&gt; wrote: >>>>>> >>>>>>> On 9/3/2016 3:18 AM, Paolo Bonzini wrote: >>>>>>>> >>>>>>>> >>>>>>>> On 02/09/2016 20:33, Kirti Wankhede wrote:

Philosophically, mdev devices should be entirely independent of one another. A user can set the same iommu context for multiple mdevs by placing them in the same container. A user should be able to stop using an mdev in one place and start using it somewhere else. It should be a fungible $TYPE device. It's an NVIDIA-only requirement that imposes this association of mdev devices into groups and I don't particularly see it as beneficial to the mdev architecture. So why make it a standard part of the interface?

We could do keying at the layer you suggest, assuming we can find something that doesn't restrict the user, but we could make that optional.

For instance, say we did key on pid, there could be an attribute in the supported types hierarchy to indicate this type supports(requires) pid-sets. Each mdev device with this attribute would create a pid-group file in sysfs where libvirt could associate the device. Only for those mdev devices requiring it.

The alternative is that we need to find some mechanism for this association that doesn't impose arbitrary requirements, and potentially usage restrictions on vendors that don't have this need. Thanks, Alex