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Date:   Tue, 12 Dec 2023 10:40:25 -0400
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     "Liu, Yi L" <yi.l.liu@intel.com>
Cc:     "Tian, Kevin" <kevin.tian@intel.com>,
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Subject: Re: [PATCH v6 2/6] iommufd: Add IOMMU_HWPT_INVALIDATE
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On Tue, Dec 12, 2023 at 01:45:16PM +0000, Liu, Yi L wrote:
> > From: Jason Gunthorpe <jgg@nvidia.com>
> > Sent: Monday, December 11, 2023 9:22 PM
> > 
> > On Mon, Dec 11, 2023 at 03:53:40PM +0800, Yi Liu wrote:
> > 
> > > > >  From that thread Jason mentioned to make the invalidation format
> > > > > part of domain allocation. If that is the direction to go then there
> > > > > won't be multiple invalidation formats per hwpt. The user should
> > > > > create multiple hwpt's per invalidation format (though mixing
> > > > > formats in one virtual platform is very unlikely)?
> > > >
> > > > I think we could do either, but I have a vauge cleanness preference
> > > > that the enums are just different? That would follow a pretty typical
> > > > pattern for a structure tag to reflect the content of the structure.
> > >
> > > Is this still following the direction to make the invalidation format
> > > part of domain allocation?
> > 
> > I think you should make it seperate
> 
> Sure. I'll add a separate enum for cache invalidation format. Just to
> see if it is good to pass down the invalidation format in the hwpt
> alloc path? So iommu driver can check if the invalidation format
> can be used for the hwpt to be allocated.

I would skip it in the invalidation. If necessary drivers can push a 0
length invalidation to do 'try and fail' discovery of supported types.

Jason