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

David Rientjes via iommu
2020-08-03T04:14:46Z

On Sun, 2 Aug 2020, Amit Pundir wrote:

> > > > Hi, I found the problematic memory region. It was a memory
> > > > chunk reserved/removed in the downstream tree but was
> > > > seemingly reserved upstream for different drivers. I failed to
> > > > calculate the length of the total region reserved downstream
> > > > correctly. And there was still a portion of memory left unmarked,
> > > > which I should have marked as reserved in my testing earlier
> > > > today.
> > > >
> > > > Sorry for all the noise and thanks Nicolas, Christoph and David
> > > > for your patience.
> > >
> > > So you'll need to patch the upstream DTS to fix this up? Do you also
> > > need my two fixes? What about the Oneplus phones? Can you send a
> > > mail with a summary of the status?
> >
> > Poco's DTS is not upstreamed yet. I have updated it for this fix
> > and sent out a newer version for review.
> > https://lkml.org/lkml/2020/8/1/184
> >
> > I didn't need to try your two add-on fixes. I'll give them a spin
> > later today.
>
> Hi Christoph,
>
> I see no obvious regressions with your twin dma-pool fixes on my
> PocoF1 phone.
>
> Caleb also confirmed that a similar reserved-memory region fix in his
> One Plus 6 device-tree worked for him too.
>

Thanks very much for the update, Amit.

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.)