RE: [EXTERNAL] Re: [PATCH v2 0/2] vhost-vdpa: Add support for NO-IOMMU mode

Srujana Challa
2024-10-14T13:23:14Z

> On Fri, Sep 20, 2024 at 07:35:28PM +0530, Srujana Challa wrote:
> > This patchset introduces support for an UNSAFE, no-IOMMU mode in the
> > vhost-vdpa driver. When enabled, this mode provides no device
> > isolation, no DMA translation, no host kernel protection, and cannot
> > be used for device assignment to virtual machines. It requires RAWIO
> > permissions and will taint the kernel.
> >
> > This mode requires enabling the
> "enable_vhost_vdpa_unsafe_noiommu_mode"
> > option on the vhost-vdpa driver and also negotiate the feature flag
> > VHOST_BACKEND_F_NOIOMMU. This mode would be useful to get better
> > performance on specifice low end machines and can be leveraged by
> > embedded platforms where applications run in controlled environment.
>
> ... and is completely broken and dangerous.
Based on the discussions in this thread https://www.spinics.net/lists/kvm/msg357569.html,
we have decided to proceed with this implementation. Could you please share any
alternative ideas or suggestions you might have?
Thanks.