Patchwork [v2,2/2,powerpc] Export memory limit via device tree

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Submitter Suzuki Poulose
Date Aug. 21, 2012, 11:42 a.m.
Message ID <>
Download mbox | patch
Permalink /patch/179049/
State Accepted, archived
Commit 4bc77a5ed215b4ec9cc39d5f55323b2e68000055
Delegated to: Benjamin Herrenschmidt
Headers show


Suzuki Poulose - Aug. 21, 2012, 11:42 a.m.
The powerpc kernel doesn't export the memory limit enforced by 'mem='
kernel parameter. This is required for building the ELF header in
kexec-tools to limit the vmcore to capture only the used memory. On
powerpc the kexec-tools depends on the device-tree for memory related
information, unlike /proc/iomem on the x86.

Without this information, the kexec-tools assumes the entire System
RAM and vmcore creates an unnecessarily larger dump.

This patch exports the memory limit, if present, via
property, so that the vmcore can be limited to the memory limit.

The prom_init seems to export this value in the same node. But doesn't
appear there.  Also the memory_limit gets adjusted with the processing of
crashkernel= parameter. This patch makes sure we get the actual limit.

The kexec-tools will use the value to limit the 'end' of the memory

Tested this patch on ppc64 and ppc32(ppc440) with a kexec-tools
patch by Mahesh.

Signed-off-by: Suzuki K. Poulose <>
Tested-by: Mahesh J. Salgaonkar <>

 arch/powerpc/kernel/machine_kexec.c |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)


diff --git a/arch/powerpc/kernel/machine_kexec.c b/arch/powerpc/kernel/machine_kexec.c
index 4074eff..fa9f6c7 100644
--- a/arch/powerpc/kernel/machine_kexec.c
+++ b/arch/powerpc/kernel/machine_kexec.c
@@ -204,6 +204,12 @@  static struct property crashk_size_prop = {
 	.value = &crashk_size,
+static struct property memory_limit_prop = {
+	.name = "linux,memory-limit",
+	.length = sizeof(unsigned long long),
+	.value = &memory_limit,
 static void __init export_crashk_values(struct device_node *node)
 	struct property *prop;
@@ -223,6 +229,12 @@  static void __init export_crashk_values(struct device_node *node)
 		crashk_size = resource_size(&crashk_res);
 		prom_add_property(node, &crashk_size_prop);
+	/*
+	 * memory_limit is required by the kexec-tools to limit the
+	 * crash regions to the actual memory used.
+	 */
+	prom_update_property(node, &memory_limit_prop);
 static int __init kexec_setup(void)