Re: [PATCH v2 06/19] drivers core: Add I/O ASID allocator

Jacob Pan
2019-04-25T18:16:32Z

Hi Christoph,

On Tue, 23 Apr 2019 23:19:03 -0700
Christoph Hellwig <hch@infradead.org> wrote:

> On Tue, Apr 23, 2019 at 04:31:06PM -0700, Jacob Pan wrote:
> > The allocator doesn't really belong in drivers/iommu because some
> > drivers would like to allocate PASIDs for devices that aren't
> > managed by an IOMMU, using the same ID space as IOMMU. It doesn't
> > really belong in drivers/pci either since platform device also
> > support PASID. Add the allocator in drivers/base.
>
> I'd still add it to drivers/iommu, just selectable separately from the
> core iommu code..
Perhaps I misunderstood. If a driver wants to use IOASIDs w/o iommu
subsystem even turned on, how could selecting from the core iommu code
help? Could you elaborate on "selectable"?

From VT-d's perspective, PASIDs are only used with IOMMU on. Jean
knows other use cases.

Jacob