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RE: [Xen-devel] [PATCH] Dom0 Kernel - Fixes forsaving/restoringMSI/MSI-X

To: "Tian, Kevin" <kevin.tian@xxxxxxxxx>, 'Jan Beulich' <jbeulich@xxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH] Dom0 Kernel - Fixes forsaving/restoringMSI/MSI-X across Dom0 S3
From: "Shan, Haitao" <haitao.shan@xxxxxxxxx>
Date: Mon, 24 Nov 2008 21:55:38 +0800
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Thread-topic: [Xen-devel] [PATCH] Dom0 Kernel - Fixes forsaving/restoringMSI/MSI-X across Dom0 S3
Yes, clear enough as Kevin said. That is what I saw why S3 failed when AHCI is 
enabled (AHCI uses MSI). I do not know whether it is also the reason that Jan 
sees the need to add force unbind support of MSI.
I have another question for saving/restoring in Xen if we do not use a new 
hypercall. Devices are controller by dom0. At the point Xen wants to save MSI 
during S3, dom0 may already places that device in D3hot state, or it may also 
cease the device's function via pci_disable_device. I doubt whether Xen can 
read device MMIO at that time.

Shan Haitao

-----Original Message-----
From: Tian, Kevin 
Sent: 2008年11月24日 21:46
To: 'Jan Beulich'
Cc: 'Keir Fraser'; Shan, Haitao; 'xen-devel@xxxxxxxxxxxxxxxxxxx'
Subject: RE: [Xen-devel] [PATCH] Dom0 Kernel - Fixes 
forsaving/restoringMSI/MSI-X across Dom0 S3

>From: Jan Beulich [mailto:jbeulich@xxxxxxxxxx] 
>Sent: Monday, November 24, 2008 9:35 PM
>>>> "Tian, Kevin" <kevin.tian@xxxxxxxxx> 24.11.08 13:53 >>>
>>It's possible that given device has been placed in D3cold state,
>>and then no change left for Xen to save.
>But isn't it the driver's resume handler that would have to 
>restore (i.e.
>re-initialize) MSI in that case?

Yes, that's my original assumption. I was told by Haitao that initial
msi support is designed in such way that dom0 is delibrately 
prevented from touch msi state, and now it looks like that Haitao
is adding back those supposed-to-be lines from native msi.c. But
I may be wrong about background and let Haitao to clarify later. :-)


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