RISC-V: Add kdump support

This patch adds support for kdump, the kernel will reserve a
region for the crash kernel and jump there on panic. In order
for userspace tools (kexec-tools) to prepare the crash kernel
kexec image, we also need to expose some information on
/proc/iomem for the memory regions used by the kernel and for
the region reserved for crash kernel. Note that on userspace
the device tree is used to determine the system's memory
layout so the "System RAM" on /proc/iomem is ignored.

I tested this on riscv64 qemu and works as expected, you may
test it by triggering a crash through /proc/sysrq_trigger:

echo c > /proc/sysrq_trigger

Signed-off-by: Nick Kossifidis <mick@ics.forth.gr>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

1 files changed, 71 insertions, 0 deletions

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index a2f4c148f02e..63c94d33e18a 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -2,6 +2,8 @@
 /*
  * Copyright (C) 2012 Regents of the University of California
  * Copyright (C) 2019 Western Digital Corporation or its affiliates.
+ * Copyright (C) 2020 FORTH-ICS/CARV
+ *  Nick Kossifidis <mick@ics.forth.gr>
  */
 
 #include <linux/init.h>
@@ -14,6 +16,7 @@
 #include <linux/libfdt.h>
 #include <linux/set_memory.h>
 #include <linux/dma-map-ops.h>
+#include <linux/crash_dump.h>
 
 #include <asm/fixmap.h>
 #include <asm/tlbflush.h>
@@ -658,6 +661,71 @@ void mark_rodata_ro(void)
 }
 #endif
 
+#ifdef CONFIG_KEXEC_CORE
+/*
+ * 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)
+{
+	unsigned long long crash_base = 0;
+	unsigned long long crash_size = 0;
+	unsigned long search_start = memblock_start_of_DRAM();
+	unsigned long search_end = memblock_end_of_DRAM();
+
+	int ret = 0;
+
+	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
+				&crash_size, &crash_base);
+	if (ret || !crash_size)
+		return;
+
+	crash_size = PAGE_ALIGN(crash_size);
+
+	if (crash_base == 0) {
+		/*
+		 * Current riscv boot protocol requires 2MB alignment for
+		 * RV64 and 4MB alignment for RV32 (hugepage size)
+		 */
+		crash_base = memblock_find_in_range(search_start, search_end,
+						    crash_size, PMD_SIZE);
+
+		if (crash_base == 0) {
+			pr_warn("crashkernel: couldn't allocate %lldKB\n",
+				crash_size >> 10);
+			return;
+		}
+	} else {
+		/* User specifies base address explicitly. */
+		if (!memblock_is_region_memory(crash_base, crash_size)) {
+			pr_warn("crashkernel: requested region is not memory\n");
+			return;
+		}
+
+		if (memblock_is_region_reserved(crash_base, crash_size)) {
+			pr_warn("crashkernel: requested region is reserved\n");
+			return;
+		}
+
+
+		if (!IS_ALIGNED(crash_base, PMD_SIZE)) {
+			pr_warn("crashkernel: requested region is misaligned\n");
+			return;
+		}
+	}
+	memblock_reserve(crash_base, crash_size);
+
+	pr_info("crashkernel: reserved 0x%016llx - 0x%016llx (%lld MB)\n",
+		crash_base, crash_base + crash_size, crash_size >> 20);
+
+	crashk_res.start = crash_base;
+	crashk_res.end = crash_base + crash_size - 1;
+}
+#endif /* CONFIG_KEXEC_CORE */
+
 void __init paging_init(void)
 {
 	setup_vm_final();
@@ -670,6 +738,9 @@ void __init misc_mem_init(void)
 	arch_numa_init();
 	sparse_init();
 	zone_sizes_init();
+#ifdef CONFIG_KEXEC_CORE
+	reserve_crashkernel();
+#endif
 	memblock_dump_all();
 }