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RE: [Xen-devel] Re: [PATCH 0/2] passthrough: make management of PCI D-st

To: Yuji Shimada <shimada-yxb@xxxxxxxxxxxxxxx>, Kouya Shimura <kouya@xxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] Re: [PATCH 0/2] passthrough: make management of PCI D-states by guest optional
From: "Cui, Dexuan" <dexuan.cui@xxxxxxxxx>
Date: Fri, 6 Mar 2009 21:41:50 +0800
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Thread-topic: [Xen-devel] Re: [PATCH 0/2] passthrough: make management of PCI D-states by guest optional
Yuji Shimada wrote:
> 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. 
>> This patch set makes the management of PCI D-states by guest optional.
>> The default is "pci_power_mgmt=0" which disables the guest OS from
>> managing D-states because it would be better to avoid the trouble than
>> advantage of low power consumption.
Is this the only reason to add the guest config parameter?
If yes, I don't think it is worthwhile to have two over-200-lines patches.
IMO we should fix the code in xend.

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

> 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.
I think it's not good to do this in ioemu. One reason is: ioemu doesn't always 
know when a guest is being shut down.e.g., we may "xm destroy" a guest.
xend should be a better place.

-- Dexuan

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