Re: [PATCH v2 1/1] fs/splice: add missing callback for inaccessible pages

[Christian Borntraeger]

On 05.05.20 14:34, Dave Hansen wrote:[...]
>> I'm not sure what exactly the requirements for your use case are; if those
>> are significantly differently, maybe we can work together to find an
>> approach that works for both?
> 
> I'm actually trying to figure out what to do with AMD's SEV.  The
> current state isn't great and, for instance, allows userspace to read
> guest ciphertext.  But, the pages come and go out of the encrypted state
> at the behest of the guest, and the kernel needs *some* mapping for the
> pages to do things like instruction emulation.
> 
> I started looking at s390 because someone said there was a similar
> problem there and suggested the hooks might work.  I couldn't figure out
> how they worked comprehensively on s390, and that's how we got here.

We are certainly not married to our approach. I would happily extend/change
this to anything that works for your case and the s390 case. So can you outline
your requirements a  bit more?