Re: [PATCH] x86: keep the crash kernel below 896 MiB

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 25/04/13 10:51, Jan Beulich wrote:
>>>> On 25.04.13 at 10:57, Warner Wang <warner.wang@hp.com> wrote:
>> When use the crashkernel=size parameter without specifying a "@xM"
>> suffix, the crashkernel will be reserved at the highest suitable
>> address of memory, this will make the kexec-tools fail to work.
>> The current kexec-tools have a limitation that it can only work
>> with crashkernel reserved under 896 MiB.  we can increase this
>> limit once kexec-tools are fixed.
>> Linux kernel itself have this code for kexec-tools limitation,
>> so I think Xen code should also have it.
> Andrew,
>
> didn't you post something along those lines at some point too,
> yet there was a reason it never got applied?
>
> Jan

Jan:
I have some low crashinfo patches but they are in.  It was for
positioning of the Xen per-cpu crash notes and the console ring.

Warner:
I am curious to know what this magic 896MiB limit is.  Do you have a
reference to the problem.

~Andrew

>
>> --- a/xen/arch/x86/setup.c
>> +++ b/xen/arch/x86/setup.c
>> @@ -943,6 +943,13 @@ void __init __start_xen(unsigned long mbi_p)
>>              }
>>          }
>>  
>> +        /*
>> +         * Keep the crash kernel below this limit.  On 64 bits, kexec-tools
>> +         * currently limits us to 896 MiB; increase this limit once kexec-tools
>> +         * are fixed.
>> +         */
>> +        e = min_t(uint64_t, e, 896 << 20);
>> +
>>          /* Don't overlap with modules. */
>>          e = consider_modules(s, e, PAGE_ALIGN(kexec_crash_area.size),
>>                               mod, mbi->mods_count, -1);
>> -- 
>> 1.7.1
>
>