x86: find offset for crashkernel reservation automatically

This patch removes the need of the crashkernel=...@offset parameter to define
a fixed offset for crashkernel reservation. That feature can be used together
with a relocatable kernel where the kexec-tools relocate the kernel and
get the actual offset from /proc/iomem.

The use case is a kernel where the .text+.data+.bss is after 16M physical
memory (debug kernel with lockdep on x86_64 can cause that) which caused a
major pain in autoconfiguration in our distribution.

Also, that patch unifies crashdump architectures a bit since IA64 has
that semantics from the very beginning of the kdump port.

Signed-off-by: Bernhard Walle <bwalle@suse.de>
Cc: vgoyal@redhat.com
Cc: Bernhard Walle <bwalle@suse.de>
Cc: kexec@lists.infradead.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 52 insertions, 18 deletions

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 2ca12d4c88fb..b3469898717e 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -422,6 +422,34 @@ static void __init reserve_setup_data(void)
  */
 
 #ifdef CONFIG_KEXEC
+
+/**
+ * Reserve @size bytes of crashkernel memory at any suitable offset.
+ *
+ * @size: Size of the crashkernel memory to reserve.
+ * Returns the base address on success, and -1ULL on failure.
+ */
+unsigned long long find_and_reserve_crashkernel(unsigned long long size)
+{
+        const unsigned long long alignment = 16<<20;    /* 16M */
+        unsigned long long start = 0LL;
+
+        while (1) {
+                int ret;
+
+                start = find_e820_area(start, ULONG_MAX, size, alignment);
+                if (start == -1ULL)
+                        return start;
+
+                /* try to reserve it */
+                ret = reserve_bootmem_generic(start, size, BOOTMEM_EXCLUSIVE);
+                if (ret >= 0)
+                        return start;
+
+                start += alignment;
+        }
+}
+
 static inline unsigned long long get_total_mem(void)
 {
         unsigned long long total;
@@ -444,30 +472,36 @@ static void __init reserve_crashkernel(void)
 
         ret = parse_crashkernel(boot_command_line, total_mem,
                         &crash_size, &crash_base);
-        if (ret == 0 && crash_size > 0) {
-                if (crash_base <= 0) {
-                        printk(KERN_INFO "crashkernel reservation failed - "
-                                        "you have to specify a base address\n");
+        if (ret != 0 || crash_size <= 0)
+                return;
+
+        /* 0 means: find the address automatically */
+        if (crash_base <= 0) {
+                crash_base = find_and_reserve_crashkernel(crash_size);
+                if (crash_base == -1ULL) {
+                        pr_info("crashkernel reservation failed. "
+                                "No suitable area found.\n");
                         return;
                 }
-
-                if (reserve_bootmem_generic(crash_base, crash_size,
-                                        BOOTMEM_EXCLUSIVE) < 0) {
-                        printk(KERN_INFO "crashkernel reservation failed - "
-                                        "memory is in use\n");
+        } else {
+                ret = reserve_bootmem_generic(crash_base, crash_size,
+                                        BOOTMEM_EXCLUSIVE);
+                if (ret < 0) {
+                        pr_info("crashkernel reservation failed - "
+                                "memory is in use\n");
                         return;
                 }
+        }
 
-                printk(KERN_INFO "Reserving %ldMB of memory at %ldMB "
-                                "for crashkernel (System RAM: %ldMB)\n",
-                                (unsigned long)(crash_size >> 20),
-                                (unsigned long)(crash_base >> 20),
-                                (unsigned long)(total_mem >> 20));
+        printk(KERN_INFO "Reserving %ldMB of memory at %ldMB "
+                        "for crashkernel (System RAM: %ldMB)\n",
+                        (unsigned long)(crash_size >> 20),
+                        (unsigned long)(crash_base >> 20),
+                        (unsigned long)(total_mem >> 20));
 
-                crashk_res.start = crash_base;
-                crashk_res.end   = crash_base + crash_size - 1;
-                insert_resource(&iomem_resource, &crashk_res);
-        }
+        crashk_res.start = crash_base;
+        crashk_res.end   = crash_base + crash_size - 1;
+        insert_resource(&iomem_resource, &crashk_res);
 }
 #else
 static void __init reserve_crashkernel(void)