Re: [PATCH v2 7/8] iommu: Export iommu_get_dma_domain

[Jacob Pan <jacob.jun.pan@linux.intel.com>]

Hi Jason,

On Tue, 28 Mar 2023 13:19:11 -0300, Jason Gunthorpe <jgg@nvidia.com> wrote:

> On Tue, Mar 28, 2023 at 08:48:22AM -0700, Jacob Pan wrote:
> 
> > > Agree. The kernel driver managing the device wants to get the current 
> > > domain of the device then iommu_get_domain_for_dev() is the right
> > > interface. It knows the domain is the dma domain.  
> > This goes back to v1 then :)
> > 
> > I thought the comments from v1 is that we don't want to check the domain
> > type is DMA domain returned by iommu_get_domain_for_dev()
> > 
> > If the driver "knows" the domain is dma domain, why can't it use
> > iommu_get_dma_domain()? seems paradoxical.  
> 
> Huh?
> 
> The DMA API operates on the current domain of the device, be it
> IDENTITY or UNMANAGED.
> 
> You have to copy whatever the current domain is to the PASID and you
> should definately not check if it is DMA or something.
> 
right, the PASID works for IOVA, passthrough. I misunderstood the v1
review comments. I will go back to use iommu_get_domain_for_dev() but w/o
checking domain types.

Thanks all,

Jacob