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SubjectRe: [PATCH 1/4] iommu/vt-d: Implement set device pasid op for default domain
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On 2023/3/2 8:59, Jacob Pan wrote:
> On VT-d platforms, legacy DMA requests without PASID use device’s
> default domain, where RID_PASID is always attached. Device drivers
> can then use the DMA API for all in-kernel DMA on the RID.
>
> Ideally, devices capable of using ENQCMDS can also transparently use the
> default domain, consequently DMA API. However, VT-d architecture
> dictates that the PASID used by ENQCMDS must be different from the
> RID_PASID value.
>
> To provide support for transparent use of DMA API with non-RID_PASID
> value, this patch implements the set_dev_pasid() function for the
> default domain. The idea is that device drivers wishing to use ENQCMDS
> to submit work on buffers mapped by DMA API will call
> iommu_attach_device_pasid() beforehand.
>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> ---
> drivers/iommu/intel/iommu.c | 32 ++++++++++++++++++++++++++++++++
> 1 file changed, 32 insertions(+)
>
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 10f657828d3a..a0cb3bc851ac 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -4665,6 +4665,10 @@ static void intel_iommu_remove_dev_pasid(struct device *dev, ioasid_t pasid)
> case IOMMU_DOMAIN_SVA:
> intel_svm_remove_dev_pasid(dev, pasid);
> break;
> + case IOMMU_DOMAIN_DMA:
> + case IOMMU_DOMAIN_DMA_FQ:
> + case IOMMU_DOMAIN_IDENTITY:
> + break;
> default:
> /* should never reach here */
> WARN_ON(1);
> @@ -4675,6 +4679,33 @@ static void intel_iommu_remove_dev_pasid(struct device *dev, ioasid_t pasid)
> intel_pasid_tear_down_entry(iommu, dev, pasid, false);
> }
>
> +static int intel_iommu_set_dev_pasid(struct iommu_domain *domain,
> + struct device *dev, ioasid_t pasid)
> +{
> + struct device_domain_info *info = dev_iommu_priv_get(dev);
> + struct dmar_domain *dmar_domain = to_dmar_domain(domain);
> + struct intel_iommu *iommu = info->iommu;
> + int ret = 0;
> +
> + if (!sm_supported(iommu) || !info)

@info has been referenced. !info check makes no sense.

Add pasid_supported(iommu).

Do you need to check whether the domain is compatible for this rid
pasid?

> + return -ENODEV;
> +
> + if (WARN_ON(pasid == PASID_RID2PASID))
> + return -EINVAL;

Add a call to domain_attach_iommu() here to get a refcount of the domain
ID. And call domain_detach_iommu() in intel_iommu_remove_dev_pasid().

> +
> + if (hw_pass_through && domain_type_is_si(dmar_domain))
> + ret = intel_pasid_setup_pass_through(iommu, dmar_domain,
> + dev, pasid);
> + else if (dmar_domain->use_first_level)
> + ret = domain_setup_first_level(iommu, dmar_domain,
> + dev, pasid);
> + else
> + ret = intel_pasid_setup_second_level(iommu, dmar_domain,
> + dev, pasid);
> +
> + return ret;
> +}

Do you need to consider pasid cache invalidation?

> +
> const struct iommu_ops intel_iommu_ops = {
> .capable = intel_iommu_capable,
> .domain_alloc = intel_iommu_domain_alloc,
> @@ -4702,6 +4733,7 @@ const struct iommu_ops intel_iommu_ops = {
> .iova_to_phys = intel_iommu_iova_to_phys,
> .free = intel_iommu_domain_free,
> .enforce_cache_coherency = intel_iommu_enforce_cache_coherency,
> + .set_dev_pasid = intel_iommu_set_dev_pasid,
> }
> };
>

Best regards,
baolu

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