RE: [PATCH 6/6] iommu/vt-d: Add domain_alloc_user op

[Liu, Yi L]

> From: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Sent: Wednesday, September 20, 2023 9:05 PM
> 
> On Wed, Sep 20, 2023 at 01:28:41PM +0800, Baolu Lu wrote:
> > >
> > > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> > > index 5db283c17e0d..491bcde1ff96 100644
> > > --- a/drivers/iommu/intel/iommu.c
> > > +++ b/drivers/iommu/intel/iommu.c
> > > @@ -4074,6 +4074,25 @@ static struct iommu_domain
> *intel_iommu_domain_alloc(unsigned type)
> > >   	return NULL;
> > >   }
> > > +static struct iommu_domain *
> > > +intel_iommu_domain_alloc_user(struct device *dev, u32 flags)
> > > +{
> > > +	struct iommu_domain *domain;
> > > +	struct intel_iommu *iommu;
> > > +
> > > +	iommu = device_to_iommu(dev, NULL, NULL);
> > > +	if (!iommu)
> > > +		return ERR_PTR(-ENODEV);
> > > +
> > > +	if ((flags & IOMMU_HWPT_ALLOC_NEST_PARENT) && !ecap_nest(iommu-
> >ecap))
> > > +		return ERR_PTR(-EOPNOTSUPP);
> 
> There is a check missing for supported flags
> 
>  if (flags & (~IOMMU_HWPT_ALLOC_NEST_PARENT))
> 	return ERR_PTR(-EOPNOTSUPP);

Well, the iommufd has such check. But I also noticed your another
reply to Weijiang. So your preference is to do the flags validation
in iommu driver instead of iommufd. Isn't it?

> > > +
> > > +	domain = iommu_domain_alloc(dev->bus);
> >
> > No need to bounce between core and driver. Just,
> >
> > 	intel_iommu_domain_alloc(IOMMU_DOMAIN_UNMANAGED);
> >
> > and fully initialize it before return.
> 
> If you are going to do that then intel_iommu_domain_alloc() should
> fully initialize the domain, not here.

I've also considered what Baolu described, but it requires to do some
extra initialization which is duplicated with iommu_domain_alloc().
So I chose this simple way.

Regards,
Yi Liu