Re: [Qemu-devel] [PATCH 00/13] IOMMU: Enable interrupt remapping for Intel IOMMU

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

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On 2016-02-19 10:58, Paolo Bonzini wrote:
> 
> 
> On 19/02/2016 10:29, Peter Xu wrote:
>> On Fri, Feb 19, 2016 at 09:34:40AM +0100, Jan Kiszka wrote:
>>> On 2016-02-19 08:43, Peter Xu wrote:
>>>> Actually there are several people within my working team knows that
>>>> I would be working on this, and I believe none of us do know your
>>>> work too... Or there must be someone telling me so...
>>>
>>> I guess we would have to match sets of people know to find out who
>>> forgot to mention the outreachy project ;) - anyway, this can always happen.
> 
> I knew about the outreachy project and forgot to mention it... but then,
> I only learnt about your effort yesterday.  :)
> 
>>> I didn't look into your approach in all details yet, and Rita also just
>>> started, she told me. So one question on yours - which looks appealing
>>> from the invasiveness POV - is how you determine the MSI source with
>>> only a single target region? I do find your changes on the IOAPIC, but
>>> none on the PCI infrastructure, which is confusing given that you say
>>> that works, no?
>>
>> Do we need to know the source of the MSI interrupt to
>> translate/deliver it? Maybe I got something missing, but could you
>> explain why we need it?
> 
> I think you're not verifying the SVT, SID and SQ fields in the IRTE.

Exactly.

> 
> The source ID can be passed to the IOMMU using the MemTxAttrs mechanism.

Ah, that's a nice new channel, resolving the need for using/passing
source-specific target memory regions for this. At least for PCI
devices, it should already be populated with the required information,
others (IOAPIC, HPET) probably require additional work to pass what I
defined as Q35_PSEUDO_BUS_PLATFORM, Q35_PSEUDO_DEVFN_IOAPIC/HPET.

Jan


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