Re: [PATCH v3 1/4] iommu/vt-d: Implement domain ops for attach_dev_pasid

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, May 10, 2022 at 02:07:01PM -0700, Jacob Pan wrote:
> +static int intel_iommu_attach_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;
> +	unsigned long flags;
> +	int ret = 0;
> +
> +	if (!sm_supported(iommu) || !info)
> +		return -ENODEV;
> +
> +	spin_lock_irqsave(&device_domain_lock, flags);
> +	/*
> +	 * If the same device already has a PASID attached, just return.
> +	 * DMA layer will return the PASID value to the caller.
> +	 */
> +	if (pasid != PASID_RID2PASID && info->pasid) {

Why check for PASID == 0 like this? Shouldn't pasid == 0 be rejected
as an invalid argument?

> +		if (info->pasid == pasid)
> +			ret = 0;

Doesn't this need to check that the current domain is the requested
domain as well? How can this happen anyhow - isn't it an error to
double attach?

> diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
> index 5af24befc9f1..55845a8c4f4d 100644
> +++ b/include/linux/intel-iommu.h
> @@ -627,6 +627,7 @@ struct device_domain_info {
>  	struct intel_iommu *iommu; /* IOMMU used by this device */
>  	struct dmar_domain *domain; /* pointer to domain */
>  	struct pasid_table *pasid_table; /* pasid table */
> +	ioasid_t pasid; /* DMA request with PASID */

And this seems wrong - the DMA API is not the only user of
attach_dev_pasid, so there should not be any global pasid for the
device.

I suspect this should be a counter of # of pasid domains attached so
that the special flush logic triggers

And rely on the core code to worry about assigning only one domain per
pasid - this should really be a 'set' function.

Jason