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

[Liu, Yi L]

> From: Yang, Weijiang <weijiang.yang@xxxxxxxxx>
> Sent: Wednesday, September 20, 2023 1:41 PM
> On 9/19/2023 5:25 PM, Yi Liu wrote:
> > This adds the domain_alloc_user op implementation. It supports allocating
> > domains to be used as parent under nested translation.
> >
> > Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
> > ---
> >   drivers/iommu/intel/iommu.c | 20 ++++++++++++++++++++
> >   1 file changed, 20 insertions(+)
> >
> > 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);
> 
> The outer caller has checked (flags & IOMMU_HWPT_ALLOC_NEST_PARENT) before it
> comes here.
> If this callback is dedicated for nested domain allocation, then you may omit the
> condition here.

This check is different. It aims to fail the call if iommu hw does not support nested.
I just realized that it may need to check if scalable mode is enabled. This should
be more accurate.

Regards,
Yi Liu