Re: [Qemu-devel] [RFC] Memory API

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2011-05-19 15:35, Anthony Liguori wrote:
> On 05/19/2011 08:26 AM, Avi Kivity wrote:
>> On 05/19/2011 04:23 PM, Anthony Liguori wrote:
>>>> Actually, things are a bit more complicated: This layer has to properly
>>>> adopt the coalescing properties of underlying regions or we cause
>>>> performance regressions to VGA emulation. That means it has to register
>>>> dispatching slots of the corresponding size and set the coalescing flag
>>>> accordingly. And it likely need to adjust them as the regions below
>>>> change.
>>>
>>>
>>> As I mentioned in another thread, I don't think we want to "design"
>>> coalescing into the API. Coalescing is something that breaks through
>>> abstractions layers and is really just a hack.
>>
>> It's impossible not to design it into the API. The layer which wants to
>> do coalescing (the device) has no idea if and where its memory is mapped.
> 
> There's two places coalescing currently matters: VGA and PCI devices.
> Since VGA is just a special PCI device, let's just focus on PCI devices.

Every frame buffer device, PCI or not, benefits from it. Don't focus on
PCI or x86.

Jan

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