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>

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 2ca12d4c88fb462f7f698ac8da94a2db8a2a493b..b3469898717e47ffec84dce0c4c11087fe90007d 100644 (file)
--- 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)