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Re: [Xen-devel] [VTD][patch 0/5] HVM device assignment using vt-d

To: "Kay, Allen M" <allen.m.kay@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [VTD][patch 0/5] HVM device assignment using vt-d
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Thu, 31 May 2007 07:49:54 +0100
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On 30/5/07 23:02, "Kay, Allen M" <allen.m.kay@xxxxxxxxx> wrote:

>> How does this new scheme work? Can it supplant the
>> ioapic_ack=new method?
>> Clearly requiring the use of a hacky command-line option to
>> make use of a
>> new core feature is not very nice to say the least.
> Basically, the calls to mask_IO_APIC_irq()/unMask_IO_APIC_irq()
> in arch/x86/io_apic.c were replaced with
> write_fake_IO_APIC_vector()/restore_real_IO_APIC_vector
> - where the fake vector is an unused vector.
> Since the global interrupt from chipset only occurs during
> masked interrupts, this avoids that chipset bug that cause
> you to switch to ioapic_ack=new last year.  I believe it can
> supplant ioapic_ack=new method.

I'm not against removing the 'new' ioapic-ack method entirely if this is
better. I just don't fully understand this replacement method yet. I'll need
a walkthrough of the new mask/unmask replacements, most likely!

 -- Keir

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