tunables vs osxsave vs checkpointing vs _dl_runtime_resolve

[Florian Weimer]

* DJ Delorie:

> Florian Weimer <fweimer@redhat.com> writes:
>> What happens if you migrate to a machine that has XSAVE/XSAVEC, but
>> requires more storage?
>
> We'd need a new tunable to always use the maximum size, or some
> specified size, I suppose.  But there are limits to the miracles we can
> perform, and "size" is not the root problem - the layout changes too!

The layout matters only if the process is captured at a very unlucky
time.  So hopefully they can just avoid that.  I think the main issue
with the size change is that it prevents restore consistently, even in
the non-race case.

For XSAVE, it would be possible to query the size each time using CPUID.

>> I expect that this is the case that people actually care about these
>> days. 8-)
>
> In this case, they just want to disable xsave completely, so it's as
> portable as possible.

But I don't think it actually is.  Disabling XSAVE won't play nicely
with the AVX2 and later calling conventions.

Thanks,
Florian