Re: [Qemu-devel] Re: [PATCH] qemu: make virtio-blk PCI compliant by default

[john cooper]

Avi Kivity wrote:
> On 09/22/2009 05:21 PM, john cooper wrote:
>>> 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.
>>    
> 
> We'll run out of bars if we expend them like that.

Agreed.  However my motivation here was to use a
single additional bar specifically to compensate
for the PCI spec imposed 256 byte size limitation
of the config space mapping.  As we're defining the
content/size of this area, future use to accommodate
additional data should be unrestricted.

If using an additional bar is still a concern I
can certainly have a look at accomplishing the
same via virtqueue scaffolding.

-john

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