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[Xen-devel] Query about cpuidle

To: <kevin.tian@xxxxxxxxx>
Subject: [Xen-devel] Query about cpuidle
From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Date: Fri, 9 Sep 2011 13:18:06 +0100
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
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Hello,

We have recently had a support escalation about Xen-4.1.1 being unable
to boot on HP BL460c G7 blades.  The problem turned out to be a null
function pointer deference (ns_to_tick in cpu_idle.c) during early boot
of dom0, in the set_cx_pminfo function.

I applied your patch, changeset 23662:2faba14bac13, about initializing
default C state information, and this appears to have fixed the problem.

However, I see in the patch that setting up the function pointers
(ns_to_tick, tick_to_ns etc) is predicated on the hypercall coming in on
CPU0.  What guarantees are in place to ensure that these function
pointers get set up?  I cant see anything obvious from the code, but
have to admit that the null pointer deference appears to have gone away.

Thanks in advance,

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


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