Re: [PATCH v6 11/15] iommu/amd: Add IO page fault notifier handler

[Jason Gunthorpe <jgg@ziepe.ca>]

On Mon, Mar 11, 2024 at 04:30:14PM +0530, Vasant Hegde wrote:
> >> +	/*
> >> +	 * PASID zero is used for requests from the I/O device without
> >> +	 * a PASID
> >> +	 */
> >> +	dev_data = dev_iommu_priv_get(&pdev->dev);
> >> +	if (event.fault.prm.pasid == 0 ||
> >> +	    event.fault.prm.pasid >= dev_data->max_pasids) {
> >> +		pr_info_ratelimited("Invalid PASID : 0x%x, device : 0x%x\n",
> >> +				    event.fault.prm.pasid, pdev->dev.id);
> >> +		goto out;
> >> +	}
> > 
> > Why even do this check? The core code is perfectly fine to take in a
> > big pasid value, it will not match anything in the xarray and just be
> > completed with error anyhow.
> 
> We just wanted to make sure device/IOMMU can handle PASID or not before passing
> it to iommu_report_device_fault().

If it can't handle PASID then the pasid xarray will be empty and it
will be fine.

Jason