Re: [RFC PATCH] iommu/xen: Add Xen PV-IOMMU driver

[Baolu Lu <baolu.lu@linux.intel.com>]

On 6/21/24 11:09 PM, Teddy Astie wrote:
> Le 19/06/2024 à 18:30, Jason Gunthorpe a écrit :
>> On Thu, Jun 13, 2024 at 01:50:22PM +0000, Teddy Astie wrote:
>>
>>> +struct iommu_domain *xen_iommu_domain_alloc(unsigned type)
>>> +{
>>> +	struct xen_iommu_domain *domain;
>>> +	u16 ctx_no;
>>> +	int ret;
>>> +
>>> +	if (type & IOMMU_DOMAIN_IDENTITY) {
>>> +		/* use default domain */
>>> +		ctx_no = 0;
>> Please use the new ops, domain_alloc_paging and the static identity domain.
> Yes, in the v2, I will use this newer interface.
> 
> I have a question on this new interface : is it valid to not have a
> identity domain (and "default domain" being blocking); well in the
> current implementation it doesn't really matter, but at some point, we
> may want to allow not having it (thus making this driver mandatory).

It's valid to not have an identity domain if "default domain being
blocking" means a paging domain with no mappings.

In the iommu driver's iommu_ops::def_domain_type callback, just always
return IOMMU_DOMAIN_DMA, which indicates that the iommu driver doesn't
support identity translation.

Best regards,
baolu