[Xen-devel] Re: [PATCH 0/2] passthrough: make management of PCI D-states by guest optional

[Yuji Shimada <shimada-yxb@xxxxxxxxxxxxxxx>]

On Fri, 6 Mar 2009 14:23:20 +0900
Kouya Shimura <kouya@xxxxxxxxxxxxxx> wrote:

> Using D3hot state of PCI devices in xen is not mature yet.
> I met domain destruction/creation troubles in some PCI cards since the
> PCI config registers can't be read with D3hot state. xend.log is attached.

xend.log shows error occurred on resetting the device.
I think programming the device to D0 state is needed before resetting
the device.

In addition to this, config register values should be saved
when domain 0 starts, because in some devices config registers
can't be read with D3 hot state. To achieve this, it is good that
pciback driver saves config register values when it is bound to the
device, resets the device, and restores config register after
resetting.

Actually resetting and saving/restoring in pciback were discussed on
xen-devel. But unfortunately they seem not to be under developing.

Another approach is that qemu programs the device to D0 state on
shutdowning of guest domain, instead of booting of guest domain.
Then, xend can reset device successfully.

Thanks,
--
Yuji Shimada

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