Re: [PATCH 4/4] dmaengine/idxd: Re-enable kernel workqueue under DMA API

[Jason Gunthorpe <jgg@nvidia.com>]

On Thu, Mar 02, 2023 at 09:47:00AM +0000, Tian, Kevin wrote:
> > From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > Sent: Thursday, March 2, 2023 9:00 AM
> > 
> >  static int idxd_enable_system_pasid(struct idxd_device *idxd)
> >  {
> > -	return -EOPNOTSUPP;
> > +	struct pci_dev *pdev = idxd->pdev;
> > +	struct device *dev = &pdev->dev;
> > +	struct iommu_domain *domain;
> > +	union gencfg_reg gencfg;
> > +	ioasid_t pasid;
> > +	int ret;
> > +
> > +	domain = iommu_get_domain_for_dev(dev);
> > +	if (!domain || domain->type == IOMMU_DOMAIN_BLOCKED)
> > +		return -EPERM;
> 
> what about UNMANAGED?

Why are we checking this anyhow?

Get the domain the DMA API is using and feed it to
iommu_attach_device_pasid(). If the driver can't mirror the DMA API's
domain onto the PASID then it will just fail the attach. A domain
cannot even be NULL on x86.

Jason