Re: [PATCH v2] SEV: QMP support for Inject-Launch-Secret

[James Bottomley <jejb@linux.ibm.com>]

On Fri, 2020-07-03 at 12:11 +0100, Dr. David Alan Gilbert wrote:
> * Tobin Feldman-Fitzthum (tobin@linux.vnet.ibm.com) wrote:
[...]
> > +    input.trans_uaddr = (uint64_t)data;
> > +    input.trans_len = data_sz;
> > +
> > +    input.guest_uaddr = (uint64_t)hva;
> 
> Thanks for changing these; although it fails a 32bit build (which is
> probably mostly pointless for SEV, but it fails the build rather than
> building it out). The easy fix here seems to be:
>    (uint64_t)(uintptr_t)

That's a pointer width issue.  The recommended way to communicate to
the compiler that we really want to cast a 32 bit pointer to a 64 bit
value is actually to cast to unsigned long before casting to pointer,
so

(uint64_t)(unsigned long)hva

Many other things work, of course, but if you follow the recommendation
you (hopefully) don't trip future compiler warnings.

James