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Re: [Xen-devel] [PATCH 0 of 5] PV on HVM Xen

To: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 0 of 5] PV on HVM Xen
From: Sheng Yang <sheng@xxxxxxxxxxxxxxx>
Date: Wed, 17 Mar 2010 17:38:37 +0800
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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On Monday 15 March 2010 20:22:23 Stefano Stabellini wrote:
> On Mon, 15 Mar 2010, Sheng Yang wrote:
> > Hi Stefano
> >
> > I've checked your patches. And one point puzzled me(I am looking into
> > pv_ops dom0 code): seems if it depends on PIRQ, it would still require to
> > do EOI(then result in vmexit) for edge triggered interrupt? (through
> > xen_pirq_chip->end). And unmask is still a heavy work required
> > vmexit?(seems it need twice vmexit, even heavier than current HVM
> > solution)
> Only when pirq_needs_eoi(irq) returns true, and this happens when
> PIRQ_NEEDS_EOI is set.
> In my patch series I am making sure PIRQ_NEEDS_EOI is never set for any
> pirq on HVM.

I would like to work on the PIRQ porting upstream Linux(I would try ACPI but 
not sure if it would make code much more complex, e.g. cpu hotplug, PCI 
hotplug... A simple version would be just using PIRQ instead of VIRQ in my 
patches, but PIRQ is flexible, I would see if I can do more with it). And we 
may not get a version exactly the same as pv_ops dom0 code in the end... I 
would try to make them similar and make the HVM part small enough, then reduce 
Jeremy's maintain effort.

Yang, Sheng

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