Re: [Xen-devel] [PATCH v4 0/4] virtio: Clean up scatterlists and use the DMA API

[Jan Kiszka <jan.kiszka@xxxxxxxxxxx>]

On 2015-07-28 18:36, Paolo Bonzini wrote:
> On 28/07/2015 15:11, Jan Kiszka wrote:
>>>>>>
>>>>>> This doesn't matter much, since the only guests that implement an IOMMU
>>>>>> in QEMU are (afaik) PPC and x86, and x86 does not yet promise any kind
>>>>>> of stability.
>>>>
>>>> Hmm I think Jan (cc) said it was already used out there.
>> Yes, no known issues with vt-d emulation for almost a year now. Error
>> reporting could be improved, and interrupt remapping is still missing,
>> but those are minor issues in this context.
> 
> On the other hand interrupt remapping is absolutely necessary for
> production use, hence my point that x86 does not promise API stability.

Well, we currently implement the features that the Q35 used to expose.
Adding interrupt remapping will require a new chipset and/or a hack
switch to ignore compatibility.

> 
> ("Any kind of stability" actually didn't include crashes; those are not
> expected :))
> 
> The Google patches for userspace PIC and IOAPIC are proceeding well, so
> hopefully we can have interrupt remapping soon.

If the day had 48 hours... I'd love to look into this, first adding QEMU
support for the new irqchip architecture.

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux

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