Re: [PATCH v1 1/1] iommu/vt-d: Enable PRI only if the device enables PASID.

[sathyanarayanan kuppuswamy]

On 2/7/19 1:15 PM, David Woodhouse wrote:
> On Thu, 2019-02-07 at 13:09 -0800, Raj, Ashok wrote:
> > You are right.. they are completely orthogonal. We just don't have
> > a way to handle the page-requests for request without PASID's.
> >
> > There are some of the vIOMMU work to pass the PRI to who owns
> > the device, and we can certainly relax it then. This is just to reflect
> > what support exists today. FWIW, even the native driver maybe be able
> > to resolve this if supported.
> As things stand, if a device makes a PRI request without a PASID, it'll
> get told that we didn't manage to bring the page in for it. Which is
> true.
>
> What's the actual problem being fixed by this patch?
Since the request is going to fail any way why go through the process of 
enabling it ? Once the functionality (PRI without PASID) is supported, 
then they can revert this patch. Just we are trying to expose whats 
currently supported clearly.
> Yes, we're going
> to want to hook up a way to pass the PRI to the right place... but why
> add *another* thing that's just going to have to be fixed, by reverting
> this patch?
--
Sathyanarayanan Kuppuswamy
Linux kernel developer