Re: Backport suggestions for Xen 4.4

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

On 24/06/14 11:38, Jan Beulich wrote:
>>>> On 24.06.14 at 12:23, <andrew.cooper3@citrix.com> wrote:
>> Some further backport suggestions, from the XenServer patch queue.
> Thanks.
>
>> Xen bugfixes:
>> * 415738e "x86/traps: make panic and reboot paths safe during early boot"
>> * d4f88fc "make the main trap handlers safe for use early during Xen boot"
> Honestly I'd rather stay away from backporting these, no matter that
> I'm convinced they're working fine.

There are pre-existing cases where it is possible to crash and attempt
to reboot before sufficiently setting up state for machine_reboot() to
be safe.  In other words, 415738e is genuine bugfix for a real customer
escalation.

>
>> ** including "\n" fix for #MC handler from b30d333
> Purely cosmetic - we're about to die anyway when this message
> gets printed, so it not being printed on its own line is the smallest
> of our problems.
>
>> * 92009d3 "x86/boot: correct CR4 setup on APs"
> This might be acceptable, but would need validation that it really
> addresses in the stable trees what it does in -unstable without the
> other early trap handling changes. The one comment it adds to
> start_secondary() suggests that this might not be the case.

The cr4 problems were completely independent from the early trap
problems, on further consideration this is not quite correct on its own
without the other early trap series (which has been backported into
XenServer)

I can do a backport to 4.4 which resolves the interaction issue with the
early trap series, if that would help.

~Andrew