Re: [RFC] /dev/ioasid uAPI proposal

Christoph Hellwig
2021-06-30T06:57:42Z

On Mon, Jun 07, 2021 at 03:25:32AM +0000, Tian, Kevin wrote:
>
> Possibly just a naming thing, but I feel it's better to just talk about
> no-snoop or non-coherent in the uAPI. Per Intel SDM wbinvd is a
> privileged instruction. A process on the host has no privilege to
> execute it. Only when this process holds a VM, this instruction matters
> as there are guest privilege levels. But having VFIO uAPI (which is
> userspace oriented) to explicitly deal with a CPU instruction which
> makes sense only in a virtualization context sounds a bit weird...

More importantly the Intel instructions here are super weird.
Pretty much every other architecture just has plan old cache
writeback/invalidate/writeback+invalidate instructions without all these
weird implications.