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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>, Guy Zana <guy@xxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [VTD][patch 0/5] HVM device assignment using vt-d
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Sun, 03 Jun 2007 09:37:20 +0100
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On 3/6/07 09:29, "Kay, Allen M" <allen.m.kay@xxxxxxxxx> wrote:

> Base on my understanding of the Neocleus' passthrough patch, it seems
> all devices sharing that interrupt will get the double number of
> interrupts.  This means if a interrupt is shared between a NIC device
> used by a HVM guest and a SATA device used by dom0, the SATA driver in
> dom0 will also get twice the number of interrupts.  Am I correct?

No, it should be the case that the device ISRs are only invoked about as
often as in your scheme. The extra interrupts are only visible to Xen, and
tell Xen to deassert the virtual INTx wire for any hvm-attached devices
which share that physical interrupt.

 -- Keir



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