Re: [PATCH v8 2/7] iommu: Move global PASID allocation from SVA to core

[Baolu Lu <baolu.lu@linux.intel.com>]

On 6/3/23 2:22 AM, Jacob Pan wrote:
> +ioasid_t iommu_alloc_global_pasid_dev(struct device *dev)
> +{
> +	int ret;
> +	ioasid_t max;
> +
> +	max = dev->iommu->max_pasids;
> +	/*
> +	 * max_pasids is set up by vendor driver based on number of PASID bits
> +	 * supported but the IDA allocation is inclusive.
> +	 */
> +	ret = ida_alloc_range(&iommu_global_pasid_ida, IOMMU_FIRST_GLOBAL_PASID, max - 1, GFP_KERNEL);
> +	if (ret < 0)
> +		return IOMMU_PASID_INVALID;
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(iommu_alloc_global_pasid_dev);

"dev->iommu->max_pasids == 0" indicates no pasid support on the device.
The code should return IOMMU_PASID_INVALID explicitly. Perhaps we can
make this function like this:

ioasid_t iommu_alloc_global_pasid_dev(struct device *dev)
{
         int ret;

         if (!dev->iommu->max_pasids)
                 return IOMMU_PASID_INVALID;

         /*
          * max_pasids is set up by vendor driver based on number of 
PASID bits
          * supported but the IDA allocation is inclusive.
          */
         ret = ida_alloc_range(&iommu_global_pasid_ida, 
IOMMU_FIRST_GLOBAL_PASID,
                               dev->iommu->max_pasids - 1, GFP_KERNEL);

         return ret < 0 ? IOMMU_PASID_INVALID : ret;
}
EXPORT_SYMBOL_GPL(iommu_alloc_global_pasid_dev);

Other change in this series looks good to me.

I hope I can queue this series including above change as part of my VT-d
update for v6.5 to Joerg if no objection.

Let's try to re-enable this key feature of Intel idxd driver in v6.5.

Best regards,
baolu