Re: [RFC] KEXEC: allocate crash note buffers at boot time v4

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

On 02/12/11 08:02, Jan Beulich wrote:
>>>> On 01.12.11 at 18:14, Andrew Cooper <andrew.cooper3@citrix.com> wrote:
> Looks good to me now except for one minor thing (below), and the
> fact that you still decided to retain the two duplicates of the size
> calculation (I'll have to remember to clean this up if you don't, unless
> Keir explicitly agrees with the duplication).

Ok - I will turn them into a start,size pair

>> +    /* Try once again to allocate room for the crash notes.  It is just possible
>> +     * that more space has become available since we last tried.  If space has
>> +     * already been allocated, kexec_init_cpu_notes() will return early with 0.
>> +     */
>> +    if ( kexec_init_cpu_notes(nr) )
>>         return -EINVAL;
> The function can fail only with -ENOMEM, so why not return this here?
>
> Jan
>

Actually, returning -EINVAL here is counter productive.  -EINVAL is used
by dom0 to work out when it has asked for each CPU.  This in itself is a
little broken because there is nothing stopping a middle CPU from being
offline at the time these hypercalls are made.  The other thing is that
there is nothing stopping an offline cpu from having a valid notes
section.  Therefore, the test of online should be removed, so -EINVAL
only gets returned for cpu out of range, or not set up notes at all in
the first place.

-- 
Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com