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Date: Tue, 22 Sep 2009 10:21:07 -0400
From: john cooper <john.cooper@redhat.com>
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Subject: Re: [Qemu-devel] Re: [PATCH] qemu: make virtio-blk PCI compliant
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To: Avi Kivity <avi@redhat.com>
Cc: john.cooper@redhat.com, Rusty Russell <rusty@rustcorp.com.au>, "Michael S. Tsirkin" <mst@redhat.com>, qemu-devel@nongnu.org, jens.axboe@oracle.com

Avi Kivity wrote:
> On 09/21/2009 06:47 PM, john cooper wrote:
>> Rusty Russell wrote:
>>
>>   
>>> Too late, but no big deal.  We just add another feature bit for the
>>> new method.  We can have a command virtqueue for queries such as this.
>>>
>>> (Interestingly, this same issue broke lguest, with the 8-bit limit on
>>> configuration space sizes).
>>>      
>> I believe the existing guest visible interface
>> is preservable as-is without introducing any
>> ATA specific knowledge into the driver.  A
>> trivial alternate R/O mapping for the page
>> into the guest is all that is required.
>>
>> I ran out of time last week to tie this off
>> but hopefully will do so shortly.
>>
>>    
> 
> Can we just read this page as a virtqueue command instead of having it
> mapped permanently?

Probably although I hadn't looked specifically
at doing so.   Mapping the data via an unused
pci bar is pretty trivial and seemed minimally
intrusive to the existing driver.

-john

-- 
john.cooper@redhat.com