Re: [Xen-devel] [PATCH] Disable Xen PowerNow! support on Opteron 2nd gen and earlier processors

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 26/1/08 00:54, "Langsdorf, Mark" <mark.langsdorf@xxxxxxx> wrote:

>> It'd be useful to have each tracing line stamped with the CPU
>> that it comes from. As it is the tracing looks very suspect
>> because the systimes on adjacent lines are much less than
>> one second, and calibration is supposed to happen no more
>> than once per second.
> 
> Keir -
> 
> There seems to be a bug in continue_hypercall_on_cpu().
> I'm getting vcpu_set_affinity() failures with error code
> -22.  Any idea what that is?

Oh crap, of course:
 * cpufreq=dom0-kernel implies dom0_vcpus_pin
 * dom0_vcpus_pin stops dom0 from migrating its VCPUs among physical CPUs
 * The check is enforced in vcpu_set_affinity(), and unfortunately causes
continue_hypercall_on_cpu() to fail

That is such an obvious bug. :-(

vcpu_set_affinity() needs to not check dom0_vcpus_pin when called from
continue_hypercall_on_cpu(). I will cook up a patch...

 Thanks!
 Keir



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