Re: revert scope for 5.8, was Re: dma-pool fixes

David Rientjes via iommu
2020-08-03T18:30:53Z

On Mon, 3 Aug 2020, Christoph Hellwig wrote:

> On Sun, Aug 02, 2020 at 09:14:41PM -0700, David Rientjes wrote:
> > Christoph: since we have atomic DMA coherent pools in 5.8 now, recall our
> > previous discussions, including Greg KH, regarding backports to stable
> > trees (we are interested in 5.4 and 5.6) of this support for the purposes
> > of confidential VM users who wish to run their own SEV-enabled guests in
> > cloud.
> >
> > Would you have any objections to backports being offered for this support
> > now? We can prepare them immediately. Or, if you would prefer we hold
> > off for a while, please let me know and we can delay it until you are more
> > comfortable. (For confidential VM users, the ability to run your own
> > unmodified stable kernel is a much different security story than a guest
> > modified by the cloud provider.)
>
> Before we start backporting I think we need the two fixes from
> the "dma pool fixes" series. Can you start reviewing them? I also
> think we should probably wait at least until -rc2 for any fallout
> before starting the backport.
>

Thanks Christoph, this makes perfect sense. I see Nicolas has refreshed
the two patches:

dma-pool: fix coherent pool allocations for IOMMU mappings
dma-pool: Only allocate from CMA when in same memory zone

and posted them again today on LKML for review. I'll review those and
we'll send a full series of backports for stable consideration for 5.4 LTS
and 5.6 around 5.9-rc2 timeframe.

Thanks!