Re: [PATCH v3 1/4] iommu: Check IOMMU_DEV_FEAT_AUX feature in aux api's

[Lu Baolu]

Hi Alex,

On 7/30/20 4:03 AM, Alex Williamson wrote:
> On Tue, 14 Jul 2020 13:57:00 +0800
> Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote:
>
> > The iommu aux-domain api's work only when IOMMU_DEV_FEAT_AUX is enabled
> > for the device. Add this check to avoid misuse.
>
> Shouldn't this really be the IOMMU driver's responsibility to test?  If
> nothing else, iommu_dev_feature_enabled() needs to get the iommu_ops
> from dev->bus->iommu_ops, which is presumably the same iommu_ops we're
> then calling from domain->ops to attach/detach the device, so it'd be
> more efficient for the IOMMU driver to error on devices that don't
> support aux.  Thanks,

Fair enough. The vendor iommu driver always knows the status of aux-
domain support. So this check is duplicated. I will drop this patch.

Best regards,
baolu

> Alex
>
> > Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > ---
> >   drivers/iommu/iommu.c | 16 +++++++++-------
> >   1 file changed, 9 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > index 1ed1e14a1f0c..e1fdd3531d65 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -2725,11 +2725,13 @@ EXPORT_SYMBOL_GPL(iommu_dev_feature_enabled);
> >    */
> >   int iommu_aux_attach_device(struct iommu_domain *domain, struct device *dev)
> >   {
> > -	int ret = -ENODEV;
> > +	int ret;
> >   
> > -	if (domain->ops->aux_attach_dev)
> > -		ret = domain->ops->aux_attach_dev(domain, dev);
> > +	if (!iommu_dev_feature_enabled(dev, IOMMU_DEV_FEAT_AUX) ||
> > +	    !domain->ops->aux_attach_dev)
> > +		return -ENODEV;
> >   
> > +	ret = domain->ops->aux_attach_dev(domain, dev);
> >   	if (!ret)
> >   		trace_attach_device_to_domain(dev);
> >   
> > @@ -2748,12 +2750,12 @@ EXPORT_SYMBOL_GPL(iommu_aux_detach_device);
> >   
> >   int iommu_aux_get_pasid(struct iommu_domain *domain, struct device *dev)
> >   {
> > -	int ret = -ENODEV;
> > +	if (!iommu_dev_feature_enabled(dev, IOMMU_DEV_FEAT_AUX) ||
> > +	    !domain->ops->aux_get_pasid)
> > +		return -ENODEV;
> >   
> > -	if (domain->ops->aux_get_pasid)
> > -		ret = domain->ops->aux_get_pasid(domain, dev);
> > +	return domain->ops->aux_get_pasid(domain, dev);
> >   
> > -	return ret;
> >   }
> >   EXPORT_SYMBOL_GPL(iommu_aux_get_pasid);
> >