Re: [PATCH RFC] PCI: Don't restore state of a device whose config space is inaccessible

[Lukas Wunner <lukas@wunner.de>]

On Sun, Oct 25, 2026 at 05:37:39PM +0100, Patryk Janik wrote:
> After a failed reset, vfio_pci_core_disable() unconditionally calls
> pci_restore_state(). When the device did not come back (FLR timed out,
> config reads return ~0), restoring state walks the extended capability
> list and rewrites the whole config space. Every one of those accesses
> stalls for a completion timeout, so the host spends minutes in soft
> lockups instead of failing fast.

Config Space Writes are Posted Requests.  There are no Completions
sent in return and consequently no Completion Timeout is observed.
So the above paragraph doesn't really make sense.

> - "PCI: Avoid FLR for NVIDIA 5090 GPU" (linux-pci, 2026-04-16), where the
>   underlying FLR failure was described as a known device firmware defect.

I assume you're referring to:

https://lore.kernel.org/r/20260416070707.3242381-1-yuan.gao@ucloud.cn/

The outcome was that there's a firmware fix available and a quirk
should at least differentiate between good and bad firmware.
Or the fix is to update the firmware and then we don't need a quirk.

Thanks,

Lukas