Re: [Qemu-ppc] [RFC PATCH 08/26] ppc/xive: add flags to the XIVE interrupt source

[Cédric Le Goater]

On 07/24/2017 01:07 PM, Benjamin Herrenschmidt wrote:
> On Mon, 2017-07-24 at 19:50 +1000, David Gibson wrote:
>> On Mon, Jul 24, 2017 at 05:00:57PM +1000, Benjamin Herrenschmidt wrote:
>>> On Mon, 2017-07-24 at 14:36 +1000, David Gibson wrote:
>>>> On Wed, Jul 05, 2017 at 07:13:21PM +0200, Cédric Le Goater wrote:
>>>>> These flags define some characteristics of the source :
>>>>>
>>>>>  - XIVE_SRC_H_INT_ESB  the Event State Buffer are controlled with a
>>>>>                        specific hcall H_INT_ESB
>>>>
>>>> What's the other option?
>>>
>>> Direct MMIO access. Normally all interrupts use normal MMIOs,
>>> each interrupts has an associated MMIO page with special MMIOs
>>> to control the source state (PQ bits). This is something I added
>>> to the PAPR spec (and the OPAL <-> Linux interface) to allow firmware
>>> to work around broken HW (which happens on some P9 versions).
>>
>> Ok.. and that's something that can be decided at runtime?
> 
> Well, at this point I think nothing will set that flag.... It's there
> for workaround around HW bugs on some chips. At least in full emu it
> shouldn't happen unless we try to emulate those bugs. Hopefully direct
> MMIO will just work.

Nevertheless I have added support for the hcall in Linux and QEMU.
To use, I think we could create a specific source. 

C.