RE: [PATCH v6 7/8] iommu/vt-d: Add nested domain allocation

[Liu, Yi L]

> From: Baolu Lu <baolu.lu@xxxxxxxxxxxxxxx>
> Sent: Saturday, October 21, 2023 11:08 AM
> 
> On 10/20/23 5:32 PM, Yi Liu wrote:
> > From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> >
> > This adds the support for IOMMU_HWPT_DATA_VTD_S1 type.
> >
> > Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
> > ---
> >   drivers/iommu/intel/iommu.c | 39 ++++++++++++++++++++++++++-----------
> >   1 file changed, 28 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> > index b47025fbdea4..c7704e7efd4a 100644
> > --- a/drivers/iommu/intel/iommu.c
> > +++ b/drivers/iommu/intel/iommu.c
> > @@ -4076,7 +4076,7 @@ intel_iommu_domain_alloc_user(struct device *dev, u32
> flags,
> >   			      struct iommu_domain *parent,
> >   			      const struct iommu_user_data *user_data)
> >   {
> > -	struct iommu_domain *domain;
> > +	bool request_nest_parent = flags & IOMMU_HWPT_ALLOC_NEST_PARENT;
> >   	struct intel_iommu *iommu;
> >
> >   	if (flags & (~IOMMU_HWPT_ALLOC_NEST_PARENT))
> > @@ -4086,18 +4086,35 @@ intel_iommu_domain_alloc_user(struct device *dev, u32
> flags,
> >   	if (!iommu)
> >   		return ERR_PTR(-ENODEV);
> >
> > -	if ((flags & IOMMU_HWPT_ALLOC_NEST_PARENT) && !ecap_nest(iommu-
> >ecap))
> > +	if (!user_data) { /* Must be PAGING domain */
> > +		struct iommu_domain *domain;
> > +
> > +		if (request_nest_parent && !ecap_nest(iommu->ecap))
> 
> Hardware capability is not sufficient. How about adding below helper:

Yes. But the sm_supported() seems a bit confusing. Is it? actually, it's
a combined check of the sm capability and software choice (use sm or
not). How about renaming it to be sm_enabled()? Although the best
enable status check is to read the SM bit in root address register. No hurry
in this circle, but may be nice to have.

> diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h
> index b5f33a7c1973..b04bbabcd696 100644
> --- a/drivers/iommu/intel/iommu.h
> +++ b/drivers/iommu/intel/iommu.h
> @@ -540,6 +540,8 @@ enum {
>   #define sm_supported(iommu)    (intel_iommu_sm &&
> ecap_smts((iommu)->ecap))
>   #define pasid_supported(iommu) (sm_supported(iommu) &&                 \
>                                   ecap_pasid((iommu)->ecap))
> +#define nested_supported(iommu)        (sm_supported(iommu) &&
>         \
> +                                ecap_nest((iommu)->ecap))
> 
>   struct pasid_entry;
>   struct pasid_state_entry;
> 
> And, use nested_supported() here and bleow
> 
> > +			return ERR_PTR(-EOPNOTSUPP);
> > +		if (parent)
> > +			return ERR_PTR(-EINVAL);
> > +		/*
> > +		 * domain_alloc_user op needs to fully initialize a domain
> > +		 * before return, so uses iommu_domain_alloc() here for
> > +		 * simple.
> > +		 */
> > +		domain = iommu_domain_alloc(dev->bus);
> > +		if (!domain)
> > +			return ERR_PTR(-ENOMEM);
> > +		return domain;
> > +	}
> > +
> > +	/* Must be nested domain */
> > +	if (!ecap_nest(iommu->ecap))
> 
> ...here.
> 
> > +		return ERR_PTR(-EOPNOTSUPP);
> > +	if (user_data->type != IOMMU_HWPT_DATA_VTD_S1)
> >   		return ERR_PTR(-EOPNOTSUPP);
> > +	if (!parent || parent->ops != intel_iommu_ops.default_domain_ops)
> > +		return ERR_PTR(-EINVAL);
> > +	if (request_nest_parent)
> > +		return ERR_PTR(-EINVAL);
> >
> > -	/*
> > -	 * domain_alloc_user op needs to fully initialize a domain
> > -	 * before return, so uses iommu_domain_alloc() here for
> > -	 * simple.
> > -	 */
> > -	domain = iommu_domain_alloc(dev->bus);
> > -	if (!domain)
> > -		domain = ERR_PTR(-ENOMEM);
> > -	return domain;
> > +	return intel_nested_domain_alloc(parent, user_data);
> >   }
> >
> >   static void intel_iommu_domain_free(struct iommu_domain *domain)
> 
> Best regards,
> baolu