Re: [PATCH v4 06/17] PCI: add SIOV and IMS capability detection

[Jason Gunthorpe]

On Wed, Nov 11, 2020 at 02:17:48AM +0000, Tian, Kevin wrote:
> > From: Jason Gunthorpe <jgg@xxxxxxxxxx>
> > Sent: Tuesday, November 10, 2020 10:24 PM
> > 
> > On Tue, Nov 10, 2020 at 06:13:23AM -0800, Raj, Ashok wrote:
> > 
> > > This isn't just for idxd, as I mentioned earlier, there are vendors other
> > > than Intel already working on this. In all cases the need for guest direct
> > > manipulation of interrupt store hasn't come up. From the discussion, it
> > > seems like there are devices today or in future that will require direct
> > > manipulation of interrupt store in the guest. This needs additional work
> > > in both the device hardware providing the right plumbing and OS work to
> > > comprehend those.
> > 
> > We'd want to see SRIOV's assigned to guests to be able to use
> > IMS. This allows a SRIOV instance in a guest to spawn SIOV's which is
> > useful.
> 
> Does your VF support both MSI/IMS or IMS only? 

Of course VF's support MSI..

> If it is the former can't we adopt a phased approach or parallel
> effort between forcing guest to use MSI and adding hypercall to
> enable IMS on VF? Finding a way to disable IMS is anyway required
> per earlier discussion when hypercall is not available, and it could
> still provide a functional though suboptimal model for such VFs.

Sure, I view that as the bare minimum

Jason