Re: [PATCH v5 09/19] vfio/pci: Allow passing zero-length fd array in VFIO_DEVICE_PCI_HOT_RESET

Jason Gunthorpe
2023-03-06T13:17:09Z

On Fri, Mar 03, 2023 at 09:55:42AM -0700, Alex Williamson wrote:

> I can't think of a reason DPDK couldn't use hot-reset. If we want to
> make it a policy, it should be enforced by code, but creating that
> policy based on a difficulty in supporting that mode with iommufd isn't
> great.

On the other hand adding code to allow device FDs in the hot reset
path that is never used and never tested isn't great either..

hot-reset does work for DPDK, it just doesn't work in the case where
DPDK would have many VFIO devices open and they have overlapping
device sets. Which, again, is something it doesn't do.

IMHO we should leave it out of the kernel and wait for a no-iommu user
to come forward that wants hot-reset of many devices. Then we can add
and test the device FD part. Most likely such a thing will never come
at this point.

Jason