[PATCH 1/3] KVM: PPC: Assemble book3s{, _hv}_rmhandlers.S separately

[Alexander Graf]

Am 11.08.2011 um 01:58 schrieb Paul Mackerras <paulus at samba.org>:

> On Tue, Aug 02, 2011 at 02:20:28PM +0200, Alexander Graf wrote:
>> On 07/23/2011 09:41 AM, Paul Mackerras wrote:
>>> 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.

Yup, currently running autotest with this and other patches applied. Will send out a pullreq soon.


Alex

> 
> Paul.
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