linux-kernel - Re: [origin tree build failure] Re: [PULL] Please pull hwpoison code for 2.6.32

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Message-ID: <20090926181134.GT30185@one.firstfloor.org>
Date:	Sat, 26 Sep 2009 20:11:34 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>,
	fengguang.wu@...el.com, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [origin tree build failure] Re: [PULL] Please pull hwpoison code for 2.6.32

On Sat, Sep 26, 2009 at 09:35:07AM -0700, Linus Torvalds wrote:
> 
> 
> On Sat, 26 Sep 2009, Andi Kleen wrote:
> > 
> > Thanks for the report. The issue comes from NODES_SHIFT=4
> > 
> > I think I tested the NUMA case, but perhaps not with full NODES_SHIFT.
> > 
> > The easy fix would be to limit NODES_SHIFT to 3 for 32bit (8 nodes max). Do you
> > have any problems with that? I doubt there are any >8 nodes NUMAQs left.
> > (last time I heard the last machine at IBM was down to < 4)
> 
> No, just say "we don't support HWPOISON on 32-bit NUMA". 
> 
> Maybe simply using something like this.

That's a reasonable solution, but I would prefer to do it the other way round 
(MEMORY_FAILURE disabling NUMA) to minimize user confusion. Also it's not
enough to just do NUMAQ, but needs all of 32bit NUMA, otherwise the NODES_SHIFT
could be set too high again.

Here's a compile tested patch (don't have a NUMAQ) implementing this:

---

x86: Don't allow 32bit NUMA together with hwpoison to avoid page flags overflow

From: Andi Kleen <ak@...ux.intel.com>
    
Otherwise the enlarged sparsemem field in page->flags overflows 32bit,
which breaks compilation.
    
Reported by Ingo Molnar.
Originally based on a patch from Linus.
    
Signed-off-by: Andi Kleen <ak@...ux.intel.com>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 9369879..384a897 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -423,6 +423,7 @@ config X86_32_NON_STANDARD
 config X86_NUMAQ
 	bool "NUMAQ (IBM/Sequent)"
 	depends on X86_32_NON_STANDARD
+	depends on !MEMORY_FAILURE
 	select NUMA
 	select X86_MPPARSE
 	---help---
@@ -1108,6 +1109,7 @@ config NUMA
 	bool "Numa Memory Allocation and Scheduler Support"
 	depends on SMP
 	depends on X86_64 || (X86_32 && HIGHMEM64G && (X86_NUMAQ || X86_BIGSMP || X86_SUMMIT && ACPI) && EXPERIMENTAL)
+	depends on !X86_32 || !MEMORY_FAILURE
 	default y if (X86_NUMAQ || X86_SUMMIT || X86_BIGSMP)
 	---help---
 	  Enable NUMA (Non Uniform Memory Access) support.
@@ -1125,6 +1127,9 @@ config NUMA
 
 	  Otherwise, you should say N.
 
+comment "32bit NUMA support requires disabling MEMORY_FAILURE"
+	depends on X86_32 && MEMORY_FAILURE
+
 comment "NUMA (Summit) requires SMP, 64GB highmem support, ACPI"
 	depends on X86_32 && X86_SUMMIT && (!HIGHMEM64G || !ACPI)
 
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