Re: [PATCH v2 0/8] Initial support for SMMUv3 nested translation

Jason Gunthorpe
2024-10-16T11:57:05Z

On Wed, Oct 16, 2024 at 10:23:49AM +0800, Zhangfei Gao wrote:

> > Nesting support requires the system to either support S2FWB or the
> > stronger CANWBS ACPI flag. This is to ensure the VM cannot bypass the
> > cache and view incoherent data, currently VFIO lacks any cache flushing
> > that would make this safe.
>
> What if the system does not support S2FWB or CANWBS, any workaround to
> passthrough?

Eventually we can add the required cache flushing to VFIO, but that
would have to be a followup.

> Currently I am testing nesting by ignoring this check.

This is probably OK, but I wouldn't run it as a production environment
with a hostile VM.

Jason