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

[Bjorn Helgaas]

[+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
general.

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.

http://forums.xilinx.com/t5/PCI-Express/PC-is-hung-if-run-the-second-program-FPGA-by-JTAG/td-p/20871
http://www.alteraforum.com/forum/archive/index.php/t-28477.html
http://www.alteraforum.com/forum/showthread.php?t=35091
https://github.com/NetFPGA/NetFPGA-public/wiki/Restore-PCIE-Configuration
http://lkml.indiana.edu/hypermail/linux/kernel/1104.3/02544.html
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