Commit 4bc77a5e authored Aug 21, 2012 by Suzuki Poulose Committed by Benjamin Herrenschmidt Sep 07, 2012

powerpc: Export memory limit via device tree



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
chosen/linux,memory-limit
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
really
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
regions.

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

Signed-off-by: Suzuki K. Poulose <suzuki@in.ibm.com>
Tested-by: Mahesh J. Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

parent a84fcd46

arch/powerpc/kernel/machine_kexec.c

+12 −0

Original line number	Diff line number	Diff line
		@@ -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)