Re: [Suggestion] PowerPC: kernel: cross compiling issue with allmodconfig

Michael Neuling
2013-03-21T22:54:50Z

Chen Gang <gang.chen@asianux.com> wrote:

> Hello All:
>
> summary:
> the root cause is no enough room in exception area (0x5500 -- 0x7000).
>
> it is caused by the patches "for saving/restre PPR":
> they consumed much space of this area (0x5500 -- 0x7000).
> for pseries_defconfig and ppc64_defconfig, it is still ok.
> but for allmodconfig and "some additional config", it will cause issue.
>
> the solving patch "Make room in exception vector area" can make room larger.
> it can let "some additional config" ok.
> but for allmodconfig, it is still not enough.
>
>
> details
> reason:
> it is caused by:
> commit number: 13e7a8e846c2ea38a552b986ea49332f965bbb7a
> commit number: 44e9309f1f357794b7ae93d5f3e3e6f11d2b8a7f
> they are "for saving/restore PPR"
> by Haren Myneni <haren@linux.vnet.ibm.com> Thu, 6 Dec 2012
> compiling result:
> pseries_defconfig: pass (cpu for POWER7)
> ppc64_defconfig: pass (cpu for POWER7)
> allmodconfig: failed (cpu for POWER7)
>
> analysing:
> solving patch:
> ------------------------------------------------------------------
> commit number: 61383407677aef05928541a00678591abea2d84c
> Author: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Date: Thu Jan 10 17:44:19 2013 +1100
>
> powerpc: Make room in exception vector area
>
> The FWNMI region is fixed at 0x7000 and the vector are now
> overflowing that with some configurations. Fix that by moving
> some hash management code out of that region as it doesn't need
> to be that close to the call sites (isn't accessed using
> conditional branches).
> ------------------------------------------------------------------
>
> but for allmodconfig (not only for "some configurations"):
> it really can reduce much overflow bytes,
> (maybe from hundreds bytes to dozens bytes)
> but still not enough (still content overflow bytes)
>
> additional trying:
> after del CONFIG_VSX and CONFIG_PPC_970_NAP in allmodconfig,
> (will reduce dozens bytes in the region .0x5500 -- .0x7000)
> it can pass compiling (not overflow).
>
>
> next:
> I am sorry:
> I am not quite familiar with the detail features of powerpc.
> it seems I am not the suitable member to continue trying.
>
> I prefer Benjamin to continue trying (just like what he has done).
>
> if Benjamin will not do it (e.g. maybe no time to do)
> I should continue: "make additional room in exception vector area".
> (if get no reply within a week: before 2013-03-28, I should continue)
>
>
>
> welcome any members' (especially Benjamin) suggestions or completions.

This is great, thanks a lot.

If you want this to be picked up by the maintainer, you'll need to add
your signed-off-by.

The signed-off-by is to indicate that your happy for it to be included
and that you're legally allowed to do so. See
http://gerrit.googlecode.com/svn/documentation/2.0/user-signedoffby.html
for more info.

Mikey

>
> thanks.
>
> :-)
>
>
> On 2013年03月15日 13:14, Chen Gang wrote:
> > 于 2013年03月15日 12:52, Michael Neuling 写道:
> >> Yep it's a known problem but no one has bothered to fix it since it
> >> doesn't happen in a config that anyone cares about like
> >> pseries_defconfig and ppc64_defconfig. We've been moving code around in
> >> this area a lot recently hence the breakage.
> >>
> >> It should be fixed though. Patches welcome. :-)
> >
> > thanks, and I should try, and very glad to try.
> >
> > :-) :-)
> >
> > excuse me, I try to provide related patch within this month (2013-03-31), is it ok ?
> > the reason is:
> > I am not familiar with ppc assembly code, neither ppc kernel,
> > so need additional time resource.
> > (originally, I worked for x86(_64) core dump analysing for kernel and user programs)
> >
> > thanks.
> >
>
>
> --
> Chen Gang
>
> Asianux Corporation
>