Re: RFC: vfio-pci API for PCI bus/slot (hot) resets

From: Bjorn Helgaas
Date: Fri Aug 02 2013 - 18:49:55 EST

[+cc linux-pci]

On Fri, Aug 2, 2013 at 3:28 PM, Benjamin Herrenschmidt
<benh@xxxxxxxxxxxxxxxxxxx> wrote:

> Right. Another use case is, I know of devices that need a fundamental
> reset (PERST) after applying a FW update.

This is a tangent from the real discussion here, but the question of
resetting a device after a firmware update concerns me. Many if not
all of our current reset interfaces save & restore the architected
parts of config space around the reset. But a reset after a firmware
update may change things like the number and type of BARs or even the
functionality of the device, so I don't think the restore is safe in

I doubt this is a big problem in general, but I have found reports of
people having to do a system reset or reboot after updating, e.g.,
FPGA images. I suppose at least some of these could be worked around
with the right hotplug incantations.
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