Re: [PATCH v3 12/12] vfio/pci: Report dev_id in VFIO_DEVICE_GET_PCI_HOT_RESET_INFO

Alex Williamson
2023-04-03T15:02:51Z

On Mon, 3 Apr 2023 09:25:06 +0000
"Liu, Yi L" <yi.l.liu@intel.com> wrote:

> > From: Liu, Yi L <yi.l.liu@intel.com>
> > Sent: Saturday, April 1, 2023 10:44 PM
>
> > @@ -791,7 +813,21 @@ static int vfio_pci_fill_devs(struct pci_dev *pdev, void *data)
> > if (!iommu_group)
> > return -EPERM; /* Cannot reset non-isolated devices */
>
> Hi Alex,
>
> Is disabling iommu a sane way to test vfio noiommu mode?

Yes

> I added intel_iommu=off to disable intel iommu and bind a device to vfio-pci.
> I can see the /dev/vfio/noiommu-0 and /dev/vfio/devices/noiommu-vfio0. Bind
> iommufd==-1 can succeed, but failed to get hot reset info due to the above
> group check. Reason is that this happens to have some affected devices, and
> these devices have no valid iommu_group (because they are not bound to vfio-pci
> hence nobody allocates noiommu group for them). So when hot reset info loops
> such devices, it failed with -EPERM. Is this expected?

Hmm, I didn't recall that we put in such a limitation, but given the
minimally intrusive approach to no-iommu and the fact that we never
defined an invalid group ID to return to the user, it makes sense that
we just blocked the ioctl for no-iommu use. I guess we can do the same
for no-iommu cdev.

BTW, what does this series apply on? I'm assuming[1], but I don't see
a branch from Jason yet. Thanks,

Alex

[1]https://lore.kernel.org/all/20230327093351.44505-1-yi.l.liu@intel.com/