On Tue, Aug 02, 2011 at 02:20:28PM +0200, Alexander Graf wrote:

On 07/23/2011 09:41 AM, Paul Mackerras wrote:

quoted

This makes arch/powerpc/kvm/book3s_rmhandlers.S and
arch/powerpc/kvm/book3s_hv_rmhandlers.S be assembled as
separate compilation units rather than having them #included in
arch/powerpc/kernel/exceptions-64s.S.  We no longer have any
conditional branches between the exception prologs in
exceptions-64s.S and the KVM handlers, so there is no need to
keep their contents close together in the vmlinux image.

In their current location, they are using up part of the limited
space between the first-level interrupt handlers and the firmware
NMI data area at offset 0x7000, and with some kernel configurations
this area will overflow (e.g. allyesconfig), leading to an
"attempt to .org backwards" error when compiling exceptions-64s.S.

Moving them out requires that we add some #includes that the
book3s_{,hv_}rmhandlers.S code was previously getting implicitly
via exceptions-64s.S.

So what if your kernel binary is bigger than the 24 bits we can jump
and the KVM code happens to be at the end? Or do we just not care
here?

Actually we can jump +/- 32MB (26 bits).  I believe that the linker
inserts trampolines if the branch target is more than 32MB away, so it
should still work if the kernel is really large and the KVM code
happens to be at the end.

Stephen Rothwell has been asking me about this patch.  He wants it in
(or something like it) so that he can get his daily linux-next powerpc
allyesconfig builds to stop failing.

Paul.