Re: [RFC PATCH v2 02/10] iommu/vt-d: Add multiple domains per device query

[Lu Baolu]

Hi,

On 09/06/2018 03:35 AM, Alex Williamson wrote:
> On Thu, 30 Aug 2018 12:09:14 +0800
> Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote:
>
> > Add the response to IOMMU_CAP_AUX_DOMAIN capability query
> > through iommu_capable(). Return true if IOMMUs support the
> > scalable mode, return false otherwise.
> >
> > Cc: Ashok Raj <ashok.raj@xxxxxxxxx>
> > Cc: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> > Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
> > Cc: Liu Yi L <yi.l.liu@xxxxxxxxx>
> > Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > ---
> >   drivers/iommu/intel-iommu.c | 31 +++++++++++++++++++++++++++++--
> >   1 file changed, 29 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> > index 3e49d4029058..891ae70e7bf2 100644
> > --- a/drivers/iommu/intel-iommu.c
> > +++ b/drivers/iommu/intel-iommu.c
> > @@ -5193,12 +5193,39 @@ static phys_addr_t intel_iommu_iova_to_phys(struct iommu_domain *domain,
> >   	return phys;
> >   }
> >   
> > +static inline bool scalable_mode_support(void)
> > +{
> > +	struct dmar_drhd_unit *drhd;
> > +	struct intel_iommu *iommu;
> > +	bool ret = true;
> > +
> > +	rcu_read_lock();
> > +	for_each_active_iommu(iommu, drhd) {
> > +		if (!sm_supported(iommu)) {
> > +			ret = false;
> > +			break;
> > +		}
> > +	}
> > +	rcu_read_unlock();
> > +
> > +	return ret;
> > +}
> > +
> >   static bool intel_iommu_capable(enum iommu_cap cap)
> >   {
> > -	if (cap == IOMMU_CAP_CACHE_COHERENCY)
> > +	switch (cap) {
> > +	case IOMMU_CAP_CACHE_COHERENCY:
> >   		return domain_update_iommu_snooping(NULL) == 1;
> > -	if (cap == IOMMU_CAP_INTR_REMAP)
> > +	case IOMMU_CAP_INTR_REMAP:
> >   		return irq_remapping_enabled == 1;
> > +	case IOMMU_CAP_AUX_DOMAIN:
> > +		return scalable_mode_support();
> > +	case IOMMU_CAP_NOEXEC:
> > +	/* PASSTHROUGH */
> > +	default:
> > +		pr_info("Unsupported capability query %d\n", cap);
> > +		break;
>
> Please don't do this, there's no reason to be noisy about a query of a
> capability that VT-d doesn't know about.  We implement capabilities
> exactly so that relevant drivers can expose a feature and others can
> happily (and quietly) ignore them.  Thanks,

Fair enough. I will remove it in the next version.

Best regards,
Lu Baolu