Re: [PATCH 1/1] iommu: Bind process address spaces to devices

[Joerg Roedel <joro@8bytes.org>]

Hi Jacob,

On Wed, Feb 27, 2019 at 01:41:29PM -0800, Jacob Pan wrote:
> On Tue, 26 Feb 2019 12:17:43 +0100
> Joerg Roedel <joro@8bytes.org> wrote:

> Just trying to understand how to use this API.
> So if we bind the same mm to two different devices, we should get two
> different iommu_sva handle, right?
> I think intel-svm still needs a flag argument for supervisor pasid etc.
> Other than that, I think both interface should work for vt-d.

I second Jean's question here, is supervisor pasid still needed with
scalable mode? What is the use-case and which mm_struct will be used for
supervisor accesses?

> Another question is that for nested SVA, we will need to bind guest mm.
> Do you think we should try to reuse this or have it separate? I am
> working on a separate API for now.

I think a separate API makes more sense. It could be somehow fit into
this as well, but having it separate is cleaner. And we already have
separate API for aux-domains, so this would be just another extension of
the IOMMU-API for using PASIDs.


> > 	int iommu_sva_get_pasid(struct iommu_sva *handle);
> If multiple bind to the same mm gets multiple handles, this API should
> retrieve the same pasid for different handle?

It can return the same handle if we store the pasid in the mm_struct,
for example ...
> Just curious why making the handle private instead of returning the
> pasid value in the handle?

... which is also the reason why I prefer the accessor function, it
allows to have the pasid not in the iommu_sva handle, but to retrieve it
from somewhere else (like the mm_struct).

Regards,

	Joerg