x86, kdump: Retore crashkernel= to allocate under 896M

Vivek found old kexec-tools does not work new kernel anymore.

So change back crashkernel= back to old behavoir, and add crashkernel_high=
to let user decide if buffer could be above 4G, and also new kexec-tools will
be needed.

-v2: let crashkernel=X override crashkernel_high=
    update description about _high will be ignored by crashkernel=X
-v3: update description about kernel-parameters.txt according to Vivek.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1366089828-19692-4-git-send-email-yinghai@kernel.org
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 19 insertions, 5 deletions

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 12349202cae7..a85a144f2052 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -507,11 +507,14 @@ static void __init memblock_x86_reserve_range_setup_data(void)
 /*
  * Keep the crash kernel below this limit.  On 32 bits earlier kernels
  * would limit the kernel to the low 512 MiB due to mapping restrictions.
+ * On 64bit, old kexec-tools need to under 896MiB.
  */
 #ifdef CONFIG_X86_32
-# define CRASH_KERNEL_ADDR_MAX  (512 << 20)
+# define CRASH_KERNEL_ADDR_LOW_MAX      (512 << 20)
+# define CRASH_KERNEL_ADDR_HIGH_MAX     (512 << 20)
 #else
-# define CRASH_KERNEL_ADDR_MAX  MAXMEM
+# define CRASH_KERNEL_ADDR_LOW_MAX      (896UL<<20)
+# define CRASH_KERNEL_ADDR_HIGH_MAX     MAXMEM
 #endif
 
 static void __init reserve_crashkernel_low(void)
@@ -525,6 +528,7 @@ static void __init reserve_crashkernel_low(void)
         int ret;
 
         total_low_mem = memblock_mem_size(1UL<<(32-PAGE_SHIFT));
+        /* crashkernel_low=YM */
         ret = parse_crashkernel_low(boot_command_line, total_low_mem,
                                                 &low_size, &base);
         if (ret != 0) {
@@ -569,14 +573,22 @@ static void __init reserve_crashkernel(void)
         const unsigned long long alignment = 16<<20;    /* 16M */
         unsigned long long total_mem;
         unsigned long long crash_size, crash_base;
+        bool high = false;
         int ret;
 
         total_mem = memblock_phys_mem_size();
 
+        /* crashkernel=XM */
         ret = parse_crashkernel(boot_command_line, total_mem,
                         &crash_size, &crash_base);
-        if (ret != 0 || crash_size <= 0)
-                return;
+        if (ret != 0 || crash_size <= 0) {
+                /* crashkernel_high=XM */
+                ret = parse_crashkernel_high(boot_command_line, total_mem,
+                                &crash_size, &crash_base);
+                if (ret != 0 || crash_size <= 0)
+                        return;
+                high = true;
+        }
 
         /* 0 means: find the address automatically */
         if (crash_base <= 0) {
@@ -584,7 +596,9 @@ static void __init reserve_crashkernel(void)
                  *  kexec want bzImage is below CRASH_KERNEL_ADDR_MAX
                  */
                 crash_base = memblock_find_in_range(alignment,
-                               CRASH_KERNEL_ADDR_MAX, crash_size, alignment);
+                                        high ? CRASH_KERNEL_ADDR_HIGH_MAX :
+                                               CRASH_KERNEL_ADDR_LOW_MAX,
+                                        crash_size, alignment);
 
                 if (!crash_base) {
                         pr_info("crashkernel reservation failed - No suitable area found.\n");