Re: [Qemu-devel] [RFC][PATCH 11/45] msi: Factor out delivery hook

[Jan Kiszka]

On 2011-10-17 15:48, Michael S. Tsirkin wrote:
> On Mon, Oct 17, 2011 at 03:41:44PM +0200, Avi Kivity wrote:
>> On 10/17/2011 03:41 PM, Michael S. Tsirkin wrote:
>>> On Mon, Oct 17, 2011 at 01:15:56PM +0200, Jan Kiszka wrote:
>>>> On 2011-10-17 12:56, Avi Kivity wrote:
>>>>> On 10/17/2011 11:27 AM, Jan Kiszka wrote:
>>>>>> So far we deliver MSI messages by writing them into the target MMIO
>>>>>> area. This reflects what happens on hardware, but imposes some
>>>>>> limitations on the emulation when introducing KVM in-kernel irqchip
>>>>>> models. For those we will need to track the message origin.
>>>>>
>>>>> Why do we need to track the message origin?  Emulated interrupt remapping?
>>>>
>>>> The origin holds the routing cache which we need to track if the message
>>>> already has a route (and that without searching long lists) and to
>>>> update that route instead of add another one.
>>>
>>> Hmm, yes, but if the device does stl_phys or something like this,
>>> it won't work with irqchip, will it? And it should, ideally.
>>
>> Why not?  it will fall back to the apic path, and use the local routing
>> cache entry there.
> 
> Does it still work with irqchip enabled? I didn't realize ...

Yep, as MSI requests that land in the APIC MMIO page are also fed into
msi_deliver and will take the normal path from there on.

Jan

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