[RFC] asm code for Hypervisor Call Instrumentation

[Paul Mackerras]

Mike Kravetz writes:

> This patch is built on top of Anton's hcall cleanup patch.  One
> remaining issue is 'where should the statistic data structures
> be updated?'.  For simplicity, I have the asm code call the
> following C routine to perform the updates.

Hmmm, doing the update in assembly would avoid the need to create a
stack frame, which would be nice...  Maybe we need to add some macros
to include/asm-powerpc/percpu.h to make it easier to access per-cpu
variables from assembly code.

Alternatively, we could put a pointer to the hcall_stats array for
each cpu in its paca.  That's very easily accessed from assembly code.

Paul.