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

[takahiro.akashi@linaro.org (AKASHI Takahiro)]

Hi,

On Wed, Jul 13, 2016 at 10:12:12AM +0100, Suzuki K Poulose wrote:
> On 12/07/16 06:05, AKASHI Takahiro wrote:
> >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 <takahiro.akashi@linaro.org>
> >Signed-off-by: Mark Salter <msalter@redhat.com>
> >Signed-off-by: Pratyush Anand <panand@redhat.com>
> >Reviewed-by: James Morse <james.morse@arm.com>
> 
> Minor nits below.
> 
> >---
> > 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.

> >
> > #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,
> >+};
> >+
> 
> >+
> >+/*
> >+ * 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) {
> 
> ...
> 
> >+		memblock_reserve(crash_base, crash_size);
> >+
> >+	} else {
> 
> ...
> 
> >+
> >+		memblock_reserve(crash_base, crash_size);
> 
> >+	}
> 
> Nit: you could move the memblock_reserve() here to a single place.

Sure.

Thanks,
-Takahiro AKASHI

> >+
> >+	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.
> 
> >+}
> >+#else
> 
> Suzuki
>