Re: [Qemu-devel] [RFC][PATCH 42/45] msix: Introduce msix_init_simple

[Jan Kiszka <jan.kiszka@web.de>]

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On 2011-10-17 16:28, Michael S. Tsirkin wrote:
> On Mon, Oct 17, 2011 at 01:27:31PM +0200, Jan Kiszka wrote:
>> On 2011-10-17 13:22, Michael S. Tsirkin wrote:
>>> On Mon, Oct 17, 2011 at 11:28:16AM +0200, Jan Kiszka wrote:
>>>> Devices models are usually not interested in specifying MSI-X
>>>> configuration details beyond the number of vectors to provide and the
>>>> BAR number to use. Layout of an exclusively used BAR and its
>>>> registration can also be handled centrally.
>>>>
>>>> This is the purpose of msix_init_simple. It provides handy services to
>>>> the existing users. Future users like device assignment may require more
>>>> detailed setup specification. For them we will (re-)introduce msix_init
>>>> with the full list of configuration option (in contrast to the current
>>>> code).
>>>>
>>>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>>>
>>> Well, this seems a bit of a code churn then, doesn't it?
>>> We are also discussing using memory BAR for virtio-pci for other
>>> stuff besides MSI-X, so the last user of the _simple variant
>>> will be ivshmem then?
>>
>> We will surely see more MSI-X users over the time. Not sure if they all
>> mix their MSIX-X BARs with other stuff. But e.g. the e1000 variant I
>> have here does not. So there should be users in the future.
>>
>> Jan
> 
> Question is, how hard is to pass in the BAR and the offset?

That is trivial. But have a look at the final simple implementation. It
also manages the container memory region for table and PBA and
registers/unregisters that container as BAR. So there is measurable
added-value.

Jan


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