Re: [PATCH v8 01/11] iommu: Add max_pasids field in struct iommu_device

[Jason Gunthorpe]

On Thu, Jun 09, 2022 at 05:25:42PM +0000, Raj, Ashok wrote:
> 
> On Tue, Jun 07, 2022 at 09:49:32AM +0800, Lu Baolu wrote:
> > Use this field to keep the number of supported PASIDs that an IOMMU
> > hardware is able to support. This is a generic attribute of an IOMMU
> > and lifting it into the per-IOMMU device structure makes it possible
> 
> There is also a per-device attribute that tells what width is supported on
> each device. When a device enables SVM, for simplicity we were proposing to
> disable SVM on devices that don't support the full width, since it adds
> additional complexity on the allocation interface. Is that factored into
> this?

I would like to see the concept of a 'global PASID' and this is the
only place we'd union all the per-device limits together. SVM can
optionally use a global PASID and ENQCMD requires it, but I don't want
to see the core code assuming everything is ENQCMD.

Jason