linux-kernel - [PATCH] Subject: x86: Move crashkernel reservation before dma32_reserve

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Message-ID: <20080825125639.26874.80623.stgit@dev.haskins.net>
Date:	Mon, 25 Aug 2008 08:58:31 -0400
From:	Gregory Haskins <ghaskins@...ell.com>
To:	srostedt@...hat.com, mingo@...e.hu, tglx@...utronix.de
Cc:	linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
	Bernhard Walle <bwalle@...e.de>,
	Gregory Haskins <ghaskins@...ell.com>
Subject: [PATCH] Subject: x86: Move crashkernel reservation before
	dma32_reserve_bootmem()

Hi Steven, Ingo, Thomas,
  Bernard (cc'd) sent me this patch for 26.3-rt3 to fix an issue where a kdump
  kernel will fail to load, thereby disabling the crashdump feature.  Please
  consider this patch for -rt4.  IIUC, this patch is already upstream in the
  .27 series.

-Greg

-----------------
From: Bernhard Walle <bernhard.walle@....de>

On a x86-64 machine (nothing special I could encounter) I had the problem that
crashkernel reservation with the usual "64M@16M" failed. While debugging that,
I encountered that dma32_reserve_bootmem() reserves a memory region which is in
that area.

Because dma32_reserve_bootmem() does not rely on a specific offset but
crashkernel does, it makes sense to move the crashkernel reservation up a bit.
I tested that patch and it works without problems. I don't see any negative
effects of that move, but maybe I oversaw something ...

While the long-term solution is to make the crashkernel reservation dynamic
(which is already done in -tip), this bug should be fixed also short-term for
2.6.26 (or 2.6.26-stable if it's too short), and that's why I made that patch.

Signed-off-by: Bernhard Walle <bwalle@...e.de>
Signed-off-by: Gregory Haskins <ghaskins@...ell.com>
---

 arch/x86/kernel/setup_64.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/setup_64.c b/arch/x86/kernel/setup_64.c
index 6dff128..158cefe 100644
--- a/arch/x86/kernel/setup_64.c
+++ b/arch/x86/kernel/setup_64.c
@@ -444,6 +444,12 @@ void __init setup_arch(char **cmdline_p)
 	contig_initmem_init(0, end_pfn);
 #endif

+	/*
+	 * dma32_reserve_bootmem() allocates bootmem which may conflict
+	 * with the crashkernel command line, so do that before
+	 */
+	reserve_crashkernel();
+
 	dma32_reserve_bootmem();

 #ifdef CONFIG_ACPI_SLEEP
@@ -484,7 +490,6 @@ void __init setup_arch(char **cmdline_p)
 		}
 	}
 #endif
-	reserve_crashkernel();

 	reserve_ibft_region();

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