[PATCH v22 1/8] arm64: kdump: reserve memory for crash dump kernel

Hi,

On Wed, Jul 13, 2016 at 10:12:12AM +0100, Suzuki K Poulose wrote:

On 12/07/16 06:05, AKASHI Takahiro wrote:

quoted

On the startup of primary kernel, the memory region used by crash dump
kernel must be specified by "crashkernel=" kernel parameter.
reserve_crashkernel() will allocate and reserve the region for later use.

User space tools, like kexec-tools, will be able to find that region as
- "Crash kernel" in /proc/iomem, or
- "linux,crashkernel-base" and "linux,crashkernel-size" under
  /sys/firmware/devicetree/base/chosen

Signed-off-by: AKASHI Takahiro <redacted>
Signed-off-by: Mark Salter <redacted>
Signed-off-by: Pratyush Anand <redacted>
Reviewed-by: James Morse <james.morse@arm.com>

Minor nits below.

quoted

---
arch/arm64/kernel/setup.c |   7 ++-
arch/arm64/mm/init.c      | 115 ++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 121 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index c1509e6..cb5eee0 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c

@@ -31,7 +31,6 @@

#include <linux/screen_info.h>
#include <linux/init.h>
#include <linux/kexec.h>
-#include <linux/crash_dump.h>
#include <linux/root_dev.h>
#include <linux/cpu.h>
#include <linux/interrupt.h>

@@ -222,6 +221,12 @@ static void __init request_standard_resources(void)

		    kernel_data.end <= res->end)
			request_resource(res, &kernel_data);
	}
+
+#ifdef CONFIG_KEXEC_CORE
+	/* User space tools will find "Crash kernel" region in /proc/iomem. */
+	if (crashk_res.end)
+		insert_resource(&iomem_resource, &crashk_res);
+#endif

nit: Could we not do this from reserve_crashkernel() ?

Reserve_crashkernel() should be called before arm64_memblock_init().
If the code above is put in reserve_crashkernel(), the inserted
resource will be gone later by calling request_resource() in
request_standard_resource() because the crashkernel memory is part of
System RAM.

quoted

#include <asm/boot.h>
#include <asm/fixmap.h>

@@ -76,6 +78,117 @@ static int __init early_initrd(char *p)

early_param("initrd", early_initrd);
#endif

+#ifdef CONFIG_KEXEC_CORE
+static unsigned long long crash_size, crash_base;
+static struct property crash_base_prop = {
+	.name = "linux,crashkernel-base",
+	.length = sizeof(u64),
+	.value = &crash_base
+};
+static struct property crash_size_prop = {
+	.name = "linux,crashkernel-size",
+	.length = sizeof(u64),
+	.value = &crash_size,
+};
+

quoted

+
+/*
+ * reserve_crashkernel() - reserves memory for crash kernel
+ *
+ * This function reserves memory area given in "crashkernel=" kernel command
+ * line parameter. The memory reserved is used by dump capture kernel when
+ * primary kernel is crashing.
+ */
+static void __init reserve_crashkernel(void)
+{
+	int ret;
+
+	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
+				&crash_size, &crash_base);
+	/* no crashkernel= or invalid value specified */
+	if (ret || !crash_size)
+		return;
+
+	if (crash_base == 0) {

...

quoted

+		memblock_reserve(crash_base, crash_size);
+
+	} else {

...

quoted

+
+		memblock_reserve(crash_base, crash_size);

quoted

+	}

Nit: you could move the memblock_reserve() here to a single place.

Sure.

Thanks,
-Takahiro AKASHI

quoted

+
+	pr_info("Reserving %lldMB of memory at %lldMB for crashkernel\n",
+		crash_size >> 20, crash_base >> 20);
+
+	crashk_res.start = crash_base;
+	crashk_res.end = crash_base + crash_size - 1;

As mentioned above, may be we could move the insert_resource() here, which
would keep the generic setup.c code cleaner and is a bit more reader friendly.

quoted

+}
+#else

Suzuki