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Date: Thu, 11 Nov 2010 19:47:52 +0100
From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 0/2] msi support for virtfs
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To: "Aneesh Kumar K. V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: qemu-devel@nongnu.org

On 11/11/10 16:37, Aneesh Kumar K. V wrote:
> On Thu, 11 Nov 2010 12:59:24 +0100, Gerd Hoffmann<kraxel@redhat.com>  wrote:
>>    Hi,
>>
>> This tiny patch series adds msi support for virtfs.  It's two patches
>> only because we need a compat property to stay compatible with -stable
>> and we don't have a pc-0.14 machine type yet, so this is added first.
>>
>
> Sorry for being dumb. But what does the above change help to achieve.

msi support makes the IRQ handling more efficient (no IRQ sharing, no 
need to ack the IRQ to the ioapic).  Look at /proc/interupts with and 
without the patch ...

The compat property is for migration compatibility:  qemu 0.14 should be 
able to migrate to 0.13 with -M pc-0.13.  To archive that we have to 
disable new stuff which affects the savevm format (msi support does).

HTH
   Gerd