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Re: [Qemu-devel] [PATCH 2/2] Add code to override IRQ 0 to INTI 2


From: Beth Kon
Subject: Re: [Qemu-devel] [PATCH 2/2] Add code to override IRQ 0 to INTI 2
Date: Mon, 27 Oct 2008 19:02:08 -0400

On Mon, 2008-10-27 at 14:52 -0500, Anthony Liguori wrote:
> Avi Kivity wrote:
> > Beth Kon wrote:
> >> This patch, provided by Anthony Liguori, maps IRQ0 to INTI2.
> >>
> >>   
> >
> > This will cause problems for kvm, which maps interrupts 1:1 without 
> > exceptions.  While we could add support for remapping, it would mean 
> > that older kernels would not be able to support an hpet.
> >
> > Isn't it possible to connect the hpet to pic irq 2 and ioapic irq 2, 
> > maintaining the 1:1 mapping?
> 
> The APIC spec says that the hpet must be connected to APIC IRQ 0 and 
> IOAPIC IRQ 2.  I don't understand GSI very well, but I think this is the 
> normally remapping of interrupts that would occur as opposed to 
> something device specific.
> 
Just a slight clarification to Anthony's words in order to avoid
confusion... The HPET spec says that the hpet, when replacing the PIT in
legacy mode must map to PIC IRQ 0 and APIC IRQ2.

> Regards,
> 
> Anthony Liguori
> 
> > (what's irq 2 connected to now?)
> >
> 
-- 
Elizabeth Kon (Beth)
IBM Linux Technology Center
Open Hypervisor Team
email: address@hidden





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