linux-kernel - Re: [PATCH] fix ACPI induced voyager compile failure

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Message-Id: <1225474922.3264.2.camel@localhost.localdomain>
Date:	Fri, 31 Oct 2008 12:42:02 -0500
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fix ACPI induced voyager compile failure

On Thu, 2008-10-30 at 23:16 +0100, Ingo Molnar wrote: 
> * James Bottomley <James.Bottomley@...senPartnership.com> wrote:
> 
> > On Thu, 2008-10-30 at 22:58 +0100, Ingo Molnar wrote:
> > > * James Bottomley <James.Bottomley@...senPartnership.com> wrote:
> > > 
> > > > >From c339b7cdc39399855ec07dfbff67304f9c7fa49a Mon Sep 17 00:00:00 2001
> > > > From: James Bottomley <James.Bottomley@...senPartnership.com>
> > > > Date: Wed, 29 Oct 2008 10:58:13 -0500
> > > > Subject: [VOYAGER] x86: don't pull asm/acpi.h into fixmap_32.h
> > > > 
> > > > If it's not needed it causes compile failures.
> > > > 
> > > > Signed-off-by: James Bottomley <James.Bottomley@...senPartnership.com>
> > > > ---
> > > >  arch/x86/include/asm/fixmap_32.h |    2 ++
> > > >  1 files changed, 2 insertions(+), 0 deletions(-)
> > > > 
> > > > diff --git a/arch/x86/include/asm/fixmap_32.h b/arch/x86/include/asm/fixmap_32.h
> > > > index 09f29ab..c3302ee 100644
> > > > --- a/arch/x86/include/asm/fixmap_32.h
> > > > +++ b/arch/x86/include/asm/fixmap_32.h
> > > > @@ -25,7 +25,9 @@ extern unsigned long __FIXADDR_TOP;
> > > >  
> > > >  #ifndef __ASSEMBLY__
> > > >  #include <linux/kernel.h>
> > > > +#ifdef CONFIG_ACPI
> > > >  #include <asm/acpi.h>
> > > > +#endif
> > > 
> > > hm, that's quite ugly - such headers are supposed to be safe even if 
> > > CONFIG_APIC is not turned on.
> > > 
> > > What kind of compiler failures are you getting, could you send the 
> > > .config that triggers it? I'm curious what the real cause of the build 
> > > failure is - the #ifdef you are adding seems to fix a symptom, not a 
> > > real bug - and maybe we can do a better fix.
> > 
> > It's the problem of voyager wanting its own definition of
> > phys_cpu_present_map.  acpi.h pulls in mpspec.h which contaminates the
> > voyager_smp.c build.
> 
> i guess voyager could use physid_mask_t just fine?
> 
> physid_mask_t is MAX_APICS derived - but it should work out fine 
> because AFAICS voyager has a maximum of 4 cpus (but definitely less 
> than say 32), while MAX_APICS never goes below 256.

Voyager has a max of 32 actually. The CPU numbering is also fixed and
identifies the processor position (for FRU replacement), so the physical
map is what we use throughout the code.  The problem with the definition
is that it makes a rather pointless distinction between physical and
logical map types ... so there'd be a lot of code churn.   It would be
really nice if physmask_t and cpumask_t could become the same type ...
then we could do all this and no-one would notice.

James


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