fadump: Reserve the memory for firmware assisted dump.

Reserve the memory during early boot to preserve CPU state data, HPTE region
and RMA (real mode area) region data in case of kernel crash. At the time of
crash, powerpc firmware will store CPU state data, HPTE region data and move
RMA region data to the reserved memory area.

If the firmware-assisted dump fails to reserve the memory, then fallback
to existing kexec-based kdump.

Most of the code implementation to reserve memory has been
adapted from phyp assisted dump implementation written by Linas Vepstas
and Manish Ahuja

This patch also introduces a config option CONFIG_FA_DUMP for firmware
assisted dump feature on Powerpc (ppc64) architecture.

Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 246 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
new file mode 100644
index 0000000..deb276a
--- /dev/null
+++ b/arch/powerpc/kernel/fadump.c
@@ -0,0 +1,246 @@
+/*
+ * Firmware Assisted dump: A robust mechanism to get reliable kernel crash
+ * dump with assistance from firmware. This approach does not use kexec,
+ * instead firmware assists in booting the kdump kernel while preserving
+ * memory contents. The most of the code implementation has been adapted
+ * from phyp assisted dump implementation written by Linas Vepstas and
+ * Manish Ahuja
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright 2011 IBM Corporation
+ * Author: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
+ */
+
+#undef DEBUG
+#define pr_fmt(fmt) "fadump: " fmt
+
+#include <linux/string.h>
+#include <linux/memblock.h>
+
+#include <asm/page.h>
+#include <asm/prom.h>
+#include <asm/rtas.h>
+#include <asm/fadump.h>
+
+static struct fw_dump fw_dump;
+
+/* Scan the Firmware Assisted dump configuration details. */
+int __init early_init_dt_scan_fw_dump(unsigned long node,
+			const char *uname, int depth, void *data)
+{
+	__be32 *sections;
+	int i, num_sections;
+	unsigned long size;
+	const int *token;
+
+	if (depth != 1 || strcmp(uname, "rtas") != 0)
+		return 0;
+
+	/*
+	 * Check if Firmware Assisted dump is supported. if yes, check
+	 * if dump has been initiated on last reboot.
+	 */
+	token = of_get_flat_dt_prop(node, "ibm,configure-kernel-dump", NULL);
+	if (!token)
+		return 0;
+
+	fw_dump.fadump_supported = 1;
+	fw_dump.ibm_configure_kernel_dump = *token;
+
+	/*
+	 * The 'ibm,kernel-dump' rtas node is present only if there is
+	 * dump data waiting for us.
+	 */
+	if (of_get_flat_dt_prop(node, "ibm,kernel-dump", NULL))
+		fw_dump.dump_active = 1;
+
+	/* Get the sizes required to store dump data for the firmware provided
+	 * dump sections.
+	 * For each dump section type supported, a 32bit cell which defines
+	 * the ID of a supported section followed by two 32 bit cells which
+	 * gives teh size of the section in bytes.
+	 */
+	sections = of_get_flat_dt_prop(node, "ibm,configure-kernel-dump-sizes",
+					&size);
+
+	if (!sections)
+		return 0;
+
+	num_sections = size / (3 * sizeof(u32));
+
+	for (i = 0; i < num_sections; i++, sections += 3) {
+		u32 type = (u32)of_read_number(sections, 1);
+
+		switch (type) {
+		case FADUMP_CPU_STATE_DATA:
+			fw_dump.cpu_state_data_size =
+					of_read_ulong(&sections[1], 2);
+			break;
+		case FADUMP_HPTE_REGION:
+			fw_dump.hpte_region_size =
+					of_read_ulong(&sections[1], 2);
+			break;
+		}
+	}
+	return 1;
+}
+
+/**
+ * fadump_calculate_reserve_size(): reserve variable boot area 5% of System RAM
+ *
+ * Function to find the largest memory size we need to reserve during early
+ * boot process. This will be the size of the memory that is required for a
+ * kernel to boot successfully.
+ *
+ * This function has been taken from phyp-assisted dump feature implementation.
+ *
+ * returns larger of 256MB or 5% rounded down to multiples of 256MB.
+ *
+ * TODO: Come up with better approach to find out more accurate memory size
+ * that is required for a kernel to boot successfully.
+ *
+ */
+static inline unsigned long fadump_calculate_reserve_size(void)
+{
+	unsigned long size;
+
+	/*
+	 * Check if the size is specified through fadump_reserve_mem= cmdline
+	 * option. If yes, then use that.
+	 */
+	if (fw_dump.reserve_bootvar)
+		return fw_dump.reserve_bootvar;
+
+	/* divide by 20 to get 5% of value */
+	size = memblock_end_of_DRAM() / 20;
+
+	/* round it down in multiples of 256 */
+	size = size & ~0x0FFFFFFFUL;
+
+	/* Truncate to memory_limit. We don't want to over reserve the memory.*/
+	if (memory_limit && size > memory_limit)
+		size = memory_limit;
+
+	return (size > MIN_BOOT_MEM ? size : MIN_BOOT_MEM);
+}
+
+/*
+ * Calculate the total memory size required to be reserved for
+ * firmware-assisted dump registration.
+ */
+static unsigned long get_fadump_area_size(void)
+{
+	unsigned long size = 0;
+
+	size += fw_dump.cpu_state_data_size;
+	size += fw_dump.hpte_region_size;
+	size += fw_dump.boot_memory_size;
+
+	size = PAGE_ALIGN(size);
+	return size;
+}
+
+int __init fadump_reserve_mem(void)
+{
+	unsigned long base, size, memory_boundary;
+
+	if (!fw_dump.fadump_enabled)
+		return 0;
+
+	if (!fw_dump.fadump_supported) {
+		printk(KERN_INFO "Firmware-assisted dump is not supported on"
+				" this hardware\n");
+		fw_dump.fadump_enabled = 0;
+		return 0;
+	}
+	/* Initialize boot memory size */
+	fw_dump.boot_memory_size = fadump_calculate_reserve_size();
+
+	/*
+	 * Calculate the memory boundary.
+	 * If memory_limit is less than actual memory boundary then reserve
+	 * the memory for fadump beyond the memory_limit and adjust the
+	 * memory_limit accordingly, so that the running kernel can run with
+	 * specified memory_limit.
+	 */
+	if (memory_limit && memory_limit < memblock_end_of_DRAM()) {
+		size = get_fadump_area_size();
+		if ((memory_limit + size) < memblock_end_of_DRAM())
+			memory_limit += size;
+		else
+			memory_limit = memblock_end_of_DRAM();
+		printk(KERN_INFO "Adjusted memory_limit for firmware-assisted"
+				" dump, now %#016llx\n",
+				(unsigned long long)memory_limit);
+	}
+	if (memory_limit)
+		memory_boundary = memory_limit;
+	else
+		memory_boundary = memblock_end_of_DRAM();
+
+	if (fw_dump.dump_active) {
+		printk(KERN_INFO "Firmware-assisted dump is active.\n");
+		/*
+		 * If last boot has crashed then reserve all the memory
+		 * above boot_memory_size so that we don't touch it until
+		 * dump is written to disk by userspace tool. This memory
+		 * will be released for general use once the dump is saved.
+		 */
+		base = fw_dump.boot_memory_size;
+		size = memory_boundary - base;
+		memblock_reserve(base, size);
+		printk(KERN_INFO "Reserved %ldMB of memory at %ldMB "
+				"for saving crash dump\n",
+				(unsigned long)(size >> 20),
+				(unsigned long)(base >> 20));
+	} else {
+		/* Reserve the memory at the top of memory. */
+		size = get_fadump_area_size();
+		base = memory_boundary - size;
+		memblock_reserve(base, size);
+		printk(KERN_INFO "Reserved %ldMB of memory at %ldMB "
+				"for firmware-assisted dump\n",
+				(unsigned long)(size >> 20),
+				(unsigned long)(base >> 20));
+	}
+	fw_dump.reserve_dump_area_start = base;
+	fw_dump.reserve_dump_area_size = size;
+	return 1;
+}
+
+/* Look for fadump= cmdline option. */
+static int __init early_fadump_param(char *p)
+{
+	if (!p)
+		return 1;
+
+	if (strncmp(p, "on", 2) == 0)
+		fw_dump.fadump_enabled = 1;
+	else if (strncmp(p, "off", 3) == 0)
+		fw_dump.fadump_enabled = 0;
+
+	return 0;
+}
+early_param("fadump", early_fadump_param);
+
+/* Look for fadump_reserve_mem= cmdline option */
+static int __init early_fadump_reserve_mem(char *p)
+{
+	if (p)
+		fw_dump.reserve_bootvar = memparse(p, &p);
+	return 0;
+}
+early_param("fadump_reserve_mem", early_fadump_reserve_mem);