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RE: [Xen-devel] Interrupt to CPU routing in HVM domains - again

To: "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx>, "John Levon" <levon@xxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] Interrupt to CPU routing in HVM domains - again
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Fri, 5 Sep 2008 20:25:15 +1000
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, bart brooks <bart_brooks@xxxxxxxxxxx>
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Thread-topic: [Xen-devel] Interrupt to CPU routing in HVM domains - again
> On 5/9/08 02:21, "John Levon" <levon@xxxxxxxxxxxxxxxxx> wrote:
> >> Have I understood correctly that only cpu 0 of the vcpu_info[]
array is
> >> ever used even if the interrupt actually occurs on another vcpu? Is
> this
> >> true for all versions of Xen? It seems that Bart's experience is
> exactly
> >> the opposite of mine - the change that fixed up the performance
> >> for me caused performance issues for him...
> >
> > I was just in this code. From what I can tell it's a requirement
> > all the domU's event channels be bound to VCPU0, since there's no
> > in Xen itself that will redirect evtchn_pending_sel from another
> > CPU0's vcpu_info, and the callback IRQ code assumes VCPU0.
> Yes, this is very likely the problem being observed.

Would I need to do a specific bind_vcpu hypercall to cause an event
channel to be bound to a vcpu != 0? I'm not doing that.

I'm thinking that Bart is seeing some weird interaction somewhere that
is causing the change that should break things to somehow make things


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