RE: [Xen-devel] [PATCH 1/5] Add MSI support to XEN

["Shan, Haitao" <haitao.shan@xxxxxxxxx>]

OK. I will update the patch and send it out again.

Best Regards
Haitao Shan

Keir Fraser wrote:
> On 28/3/08 09:49, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:
> 
>>> Yes, the synchronisation is pretty easy though. We just have to add
>>> a layer of emulation to PV guest accesses to 0xcf8/0xcfc.
>> 
>> Yes, a small tricky however is, the owner vcpu may be scheduled
>> out between 0xcf8 and 0xcfc access, when another pcpu is trying
>> to access PCI config space like masking MSI within do_IRQ...
>> Maybe Xen need to emulate 0xcf8/0xcfc pair without return to
>> guest in the middle. :-)
> 
> Not at all. You track the guest's 0xcf8 value in the vcpu structure,
> and issue the physical 0xcf8/0xcfc access as a pair, under a
> spinlock, whenever the guest writes 0xcfc.
> 
>  -- Keir

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