Re: [RFC PATCH v3 1/2] iommu: Add capability IOMMU_CAP_VIOMMU

[Lu Baolu]

Hi,

On 2021/1/15 14:31, Leon Romanovsky wrote:
> On Fri, Jan 15, 2021 at 07:49:47AM +0800, Lu Baolu wrote:
> > Hi Leon,
> >
> > On 1/14/21 9:26 PM, Leon Romanovsky wrote:
> > > On Thu, Jan 14, 2021 at 09:30:02AM +0800, Lu Baolu wrote:
> > > > Some vendor IOMMU drivers are able to declare that it is running in a VM
> > > > context. This is very valuable for the features that only want to be
> > > > supported on bare metal. Add a capability bit so that it could be used.
> > >
> > > And how is it used? Who and how will set it?
> >
> > Use the existing iommu_capable(). I should add more descriptions about
> > who and how to use it.
>
> I want to see the code that sets this capability.

Currently we have Intel VT-d and the virt-iommu setting this capability.

 static bool intel_iommu_capable(enum iommu_cap cap)
 {
 	if (cap == IOMMU_CAP_CACHE_COHERENCY)
 		return domain_update_iommu_snooping(NULL) == 1;
 	if (cap == IOMMU_CAP_INTR_REMAP)
 		return irq_remapping_enabled == 1;
+	if (cap == IOMMU_CAP_VIOMMU)
+		return caching_mode_enabled();

 	return false;
 }

And,

+static bool viommu_capable(enum iommu_cap cap)
+{
+	if (cap == IOMMU_CAP_VIOMMU)
+		return true;
+
+	return false;
+}

Best regards,
baolu