Re: [PATCH RFC] iommu: Enable per-device SSID space for SVA

[Joonwon Kang]

> > We have multiple processes and a single device, those processes want to
> > do SVA with the same device, and only one process will do SVA with the
> > device at a time. Though, the problem occurs even when irrelevant
> > processes allocate the PASIDs from the global PASID space for their own
> > irrelevant purposes.
> 
> The only way to allocate a PASID from the global PASID space is to
> establish another SVA, so you have multiple devices doing SVA?

Another way is via iommu_alloc_global_pasid() [1] and it does not require
SVA. No, we currently do not have multiple devices doing SVA. But, the
problem is that it is out of our control when any device is to allocate a
PASID or do SVA for its own purpose.

[1] https://lore.kernel.org/all/20230802212427.1497170-3-jacob.jun.pan@xxxxxxxxxxxxxxx/

Thanks,
Joonwon Kang