RE: [PATCH v4 09/12] iommu/vt-d: Add iotlb flush for nested domain

[Tian, Kevin]

> From: Nicolin Chen <nicolinc@xxxxxxxxxx>
> Sent: Thursday, August 10, 2023 4:17 AM
> 
> On Wed, Aug 09, 2023 at 04:19:01PM -0300, Jason Gunthorpe wrote:
> > On Wed, Aug 09, 2023 at 12:12:25PM -0700, Nicolin Chen wrote:
> > > On Wed, Aug 09, 2023 at 01:24:56PM -0300, Jason Gunthorpe wrote:
> > > > Similarly for managing the array of invalidation commands.
> > >
> > > You mean an embedded uptr inside a driver user data struct right?
> > > Sure, that should go through the new helper too.
> >
> > If we are committed that all drivers have to process an array then put
> > the array in the top level struct and pass it in the same user_data
> > struct and use another helper to allow the driver to iterate through
> > it.
> 
> I see. Both VTD and SMMU pass uptr to the arrays of invalidation
> commands/requests. The only difference is that SMMU's array is a
> ring buffer other than a plain one indexing from the beginning.
> But the helper could take two index inputs, which should work for
> VTD case too. If another IOMMU driver only supports one request,
> rather than a array of requests, we can treat that as a single-
> entry array.
> 

I like this approach.