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[Xen-devel] Re: [PATCH 1/2] x86, hvm: allow another vcpu to receive PIT

To: Kouya Shimura <kouya@xxxxxxxxxxxxxx>
Subject: [Xen-devel] Re: [PATCH 1/2] x86, hvm: allow another vcpu to receive PIT IRQ (support kexec/kdump on hvm)
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Wed, 01 Jul 2009 08:55:35 +0100
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On 01/07/2009 05:49, "Kouya Shimura" <kouya@xxxxxxxxxxxxxx> wrote:

> This doesn't work since the ioapic is completely disabled.
> I've found a interesting thread in LKML archives.
> Subject: [PATCH] kexec: force x86_64 arches to boot kdump kernels on boot cpu
> http://lkml.org/lkml/2007/11/26/346
> Probably we should fix the guest bios(MP table, ioapic initialization).

So... You want virtual wire through IO-APIC?

Still some logic changes to vpt.c will be required, since platform timers
only tick and generate interrupts when vpt logic is executed on vcpu0's
return-to-guest path. Same for irq passthrough (handled by your patch 2/2).

Hmmm... Okay I think this might be workable. Device passthru and vpt
subsystems could be fired off of whichever vcpu owns the LAPIC identifier
currently programmed into IOAPIC0:PIN0, rather than being hardwired to

 -- Keir

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