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RE: [Xen-devel] [PATCH] Dom0 Kernel - Fixes for saving/restoringMSI/MSI-

To: 'Keir Fraser' <keir.fraser@xxxxxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxxxx>, "Shan, Haitao" <haitao.shan@xxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH] Dom0 Kernel - Fixes for saving/restoringMSI/MSI-X across Dom0 S3
From: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
Date: Mon, 24 Nov 2008 20:53:04 +0800
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Thread-topic: [Xen-devel] [PATCH] Dom0 Kernel - Fixes for saving/restoringMSI/MSI-X across Dom0 S3
>From: Keir Fraser
>Sent: Monday, November 24, 2008 8:04 PM
>On 24/11/08 11:41, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:
>>>>> "Shan, Haitao" <haitao.shan@xxxxxxxxx> 24.11.08 12:03 >>>
>>> With this patch, MSI/MSI-X capabilities and tables are 
>saved in Dom0 when
>>> S3 and restored when resume. Actually, this is also the 
>approach that
>>> kernel takes. The only concern is that Dom0 should not 
>touch MSI/MSI-X,
>>> they are owned by VMM itself. Maybe adding a hypercall to 
>instruct Xen to
>>> do the saving/restoring is good. I wonder whether the 
>reason is strong
>>> enough for adding a hypercall for such purpose.
>> Is it at all necessary to use a hypercall here? Shouldn't 
>Xen itself be able
>> to
>> do the necessary saving/restoring (just like it does for IO-APIC)?
>I was thinking the same thing. Haitao: shall I hold off on 
>your original
>patch while we think about this?

It's possible that given device has been placed in D3cold state,
and then no change left for Xen to save.

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