Re: [PATCH 0/3] Fix virtio-blk issue with SWIOTLB

[Jason Wang]

On 2019/1/14 äå5:50, Christoph Hellwig wrote:
> On Mon, Jan 14, 2019 at 05:41:56PM +0800, Jason Wang wrote:
> > On 2019/1/11 äå5:15, Joerg Roedel wrote:
> > > On Fri, Jan 11, 2019 at 11:29:31AM +0800, Jason Wang wrote:
> > > > Just wonder if my understanding is correct IOMMU_PLATFORM must be set for
> > > > all virtio devices under AMD-SEV guests?
> > > Yes, that is correct. Emulated DMA can only happen on the SWIOTLB
> > > aperture, because that memory is not encrypted. The guest bounces the
> > > data then to its encrypted memory.
> > >
> > > Regards,
> > >
> > > 	Joerg
> >
> > Thanks, have you tested vhost-net in this case. I suspect it may not work
> Which brings me back to my pet pevee that we need to take actions
> that virtio uses the proper dma mapping API by default with quirks
> for legacy cases.  The magic bypass it uses is just causing problems
> over problems.


Yes, I fully agree with you. This is probably an exact example of such 
problem.

Thanks