Re: [PATCH v5 5/5] pci: Suspend iommu function prior to resetting a device

[Nicolin Chen <nicolinc@nvidia.com>]

On Mon, Nov 17, 2025 at 04:52:05AM +0000, Tian, Kevin wrote:
> > From: Nicolin Chen <nicolinc@nvidia.com>
> > Sent: Saturday, November 15, 2025 2:01 AM
> > 
> > On Fri, Nov 14, 2025 at 09:45:31AM +0000, Tian, Kevin wrote:
> > > > From: Nicolin Chen <nicolinc@nvidia.com>
> > > > Sent: Tuesday, November 11, 2025 1:13 PM
> > > >
> > > > +/*
> > > > + * Per PCIe r6.3, sec 10.3.1 IMPLEMENTATION NOTE, software disables
> > ATS
> > > > before
> > > > + * initiating a reset. Notify the iommu driver that enabled ATS.
> > > > + */
> > > > +int pci_reset_iommu_prepare(struct pci_dev *dev)
> > > > +{
> > > > +	if (pci_ats_supported(dev))
> > > > +		return iommu_dev_reset_prepare(&dev->dev);
> > > > +	return 0;
> > > > +}
> > >
> > > the comment says "driver that enabled ATS", but the code checks
> > > whether ATS is supported.
> > >
> > > which one is desired?
> > 
> > The comments says "the iommu driver that enabled ATS". It doesn't
> > conflict with what the PCI core checks here?
> 
> actually this is sent to all IOMMU drivers. there is no check on whether
> a specific driver has enabled ATS in this path.

But the comment doesn't say "check"..

How about "Notify the iommu driver that enables/disables ATS"?

The point is that pci_enable_ats() is called in iommu drivers.

> > > > +	/* Have to call it after waiting for pending DMA transaction */
> > > > +	ret = pci_reset_iommu_prepare(dev);
> > > > +	if (ret) {
> > > > +		pci_err(dev, "failed to stop IOMMU\n");
> > >
> > > the error message could be more informative.
> > 
> > OK. Perhaps print the ret value.
> > 
> 
> and mention that it's for PCI reset.

OK.

Thanks
Nicolin