Re: kexec load failure introduced by "x86, memblock: Replace e820_/_earlystring with memblock_"

[Yinghai Lu]

On 09/27/2010 04:21 AM, caiqian@xxxxxxxxxx wrote:
> 
> ----- "CAI Qian" <caiqian@xxxxxxxxxx> wrote:
> 
>> ----- "Yinghai Lu" <yinghai@xxxxxxxxxx> wrote:
>>
>>> Please check this one on top of tip or next.
>> This failed for both trees.
>> [root@localhost linux-next]# patch -Np1 <memblock.patch
>> patching file arch/x86/kernel/setup.c
>> Hunk #1 FAILED at 516.
>> 1 out of 1 hunk FAILED -- saving rejects to file
>> arch/x86/kernel/setup.c.rej
> After manually applied the patch on the top of the latest mmotm tree, now there was no /proc/vmcore exported to the second kernel anymore. It could be the results of other recent commits in mmotm though. It said,
> 
> Warning: Core image elf header is notsane
> Kdump: vmcore not initialized
> 
> Here is the dmesg from the second kernel,
> 
> Initializing cgroup subsys cpuset
> Linux version 2.6.36-rc5-mm1+ (root@xxxxxxxxxxxxxxxxxxxxx) (gcc version 4.4.4 20100726 (Red Hat 4.4.4-13) (GCC) ) #6 SMP Mon Sep 27 07:00:15 EDT 2010
> Command line: ro root=/dev/mapper/VolGroup-lv_root rd_LVM_LV=VolGroup/lv_root rd_LVM_LV=VolGroup/lv_swap rd_NO_LUKS rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us rhgb quiet console=tty0 console=ttyS0,115200 crashkernel=128M irqpoll maxcpus=1 reset_devices cgroup_disable=memory  memmap=exactmap memmap=640K@0K memmap=130408K@32768K elfcorehdr=163176K kexec_jump_back_entry=0x000000000232f063
> BIOS-provided physical RAM map:
>  BIOS-e820: 0000000000000100 - 000000000009f400 (usable)
>  BIOS-e820: 000000000009f400 - 00000000000a0000 (reserved)
>  BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
>  BIOS-e820: 0000000000100000 - 00000000dfffb000 (usable)
>  BIOS-e820: 00000000dfffb000 - 00000000e0000000 (reserved)
>  BIOS-e820: 00000000fffbc000 - 0000000100000000 (reserved)
>  BIOS-e820: 0000000100000000 - 0000000ca0000000 (usable)
> last_pfn = 0xca0000 max_arch_pfn = 0x400000000
> NX (Execute Disable) protection: active
> user-defined physical RAM map:
>  user: 0000000000000000 - 00000000000a0000 (usable)
>  user: 0000000002000000 - 0000000009f5a000 (usable)
...

> Dquot-cache hash table entries: 512 (order 0, 4096 bytes)
> Warning: Core image elf header is notsane
> Kdump: vmcore not initialized
> 
>>

it should work on tip..., I tested on RHEL 6.0 beta.
with
/etc/init.d/kdump restart

BTW, second kernel is not supposed to take crashkernel=128M again.
/etc/init.d/kdump scripts remove that while using /proc/cmdline.

please refer
http://people.redhat.com/mingo/tip.git/readme.txt
to get tip/master

and apply attached patch
cat crashkernel_limit.patch | patch -p1

Thanks

Yinghai

[PATCH -v2] x86, memblock: Fix crashkernel allocation

Cai Qian found crashkernel is broken with x86 memblock changes
1. crashkernel=128M@32M always reported that range is used, even first kernel is small
   no one use that range
2. always get following report when using "kexec -p"
	Could not find a free area of memory of a000 bytes...
	locate_hole failed

The root cause is that generic memblock_find_in_range() will try to get range from top_down.
But crashkernel do need from low and specified range.

Let's limit the target range with rash_base + crash_size to make sure that
We get range from bottom.

-v2: don't limit it with 0xffffffff, in case kexec will use bzImage 64bit entry or vmlinux,
     and try to allocate huge area for crashkernel.

Reported-and-Bisected-by: CAI Qian <caiqian@xxxxxxxxxx>
Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>

---
 arch/x86/kernel/setup.c |   19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

Index: linux-2.6/arch/x86/kernel/setup.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/setup.c
+++ linux-2.6/arch/x86/kernel/setup.c
@@ -516,19 +516,28 @@ static void __init reserve_crashkernel(v
 
 	/* 0 means: find the address automatically */
 	if (crash_base <= 0) {
+		unsigned long long start = 0;
 		const unsigned long long alignment = 16<<20;	/* 16M */
 
-		crash_base = memblock_find_in_range(alignment, ULONG_MAX, crash_size,
-				 alignment);
-		if (crash_base == MEMBLOCK_ERROR) {
+		crash_base = alignment;
+		while ((crash_base + crash_size) <= total_mem) {
+			start = memblock_find_in_range(crash_base,
+				crash_base + crash_size, crash_size, alignment);
+
+			if (start == crash_base)
+				break;
+
+			crash_base += alignment;
+		}
+		if (start != crash_base) {
 			pr_info("crashkernel reservation failed - No suitable area found.\n");
 			return;
 		}
 	} else {
 		unsigned long long start;
 
-		start = memblock_find_in_range(crash_base, ULONG_MAX, crash_size,
-				 1<<20);
+		start = memblock_find_in_range(crash_base,
+				 crash_base + crash_size, crash_size, 1<<20);
 		if (start != crash_base) {
 			pr_info("crashkernel reservation failed - memory is in use.\n");
 			return;