Re: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and allocation APIs

Auger Eric
2021-04-16T15:00:45Z

Hi Jason,

On 4/16/21 4:34 PM, Jason Gunthorpe wrote:
> On Fri, Apr 16, 2021 at 04:26:19PM +0200, Auger Eric wrote:
>
>> This was largely done during several confs including plumber, KVM forum,
>> for several years. Also API docs were shared on the ML. I don't remember
>> any voice was raised at those moments.
>
> I don't think anyone objects to the high level ideas, but
> implementation does matter. I don't think anyone presented "hey we
> will tunnel an uAPI through VFIO to the IOMMU subsystem" - did they?

At minimum
https://events19.linuxfoundation.cn/wp-content/uploads/2017/11/Shared-Virtual-Memory-in-KVM_Yi-Liu.pdf

But most obviously everything is documented in
Documentation/userspace-api/iommu.rst where the VFIO tunneling is
clearly stated ;-)

But well let's work together to design a better and more elegant
solution then.

Thanks

Eric
>
> Look at the fairly simple IMS situation, for example. This was
> presented at plumbers too, and the slides were great - but the
> implementation was too hacky. It required a major rework of the x86
> interrupt handling before it was OK.
>
> Jason
>