Re: KEXEC: allocate crash note buffers at boot time v5

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

On 02/12/11 16:11, Jan Beulich wrote:
>>>> On 02.12.11 at 16:59, Andrew Cooper <andrew.cooper3@citrix.com> wrote:
>> On 02/12/11 15:43, Jan Beulich wrote:
>>> I just had another look at the Dom0 side of things, and I fail to see why
>>> you think boot time allocation is necessary: All Dom0 does with the
>>> provided info is set up the resource tree. The data doesn't get stored
>>> for any post-boot use. What am I overlooking?
>> /sbin/kexec opens /proc/iomem and looks for "Crash note" and interprets
>> the range values.  This is how it grabs the locations to pack into its
>> magic binary package.
> So how does the hotplug scenario then get handled on native? I can't
> imagine they expect things to remain stable across CPU unplug and
> re-activation.
>
> Jan

I am not how (or even if) the hotplug condition is handled on native.  I
guess it depends on what is put into the resource tree on boot.  With my
patch, Xen will give crash areas for all pcpus up to nr_cpu_ids, which
covers all the cases.  The worst that will happen is that some crash
notes do not get written if certain cpus are offline at the time of a crash.

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