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Re: [Xen-devel] Kernel crash with acpi_processor, cpu_idle and intel_idle =y

Hi Konrad,

> > CONFIG_INTEL_IDLE to y then I cannot boot Xen; there is a crash. If
> > I turn CONFIG_INTEL_IDLE off then the boot goes well and, after
> > dom0 has booted, xenpm works and gives some sane output, see below.
> > I have tested this with kernels 3.2 to 3.4.6. 
> > 
> > Is it impossible to use INTEL_IDLE with Xen? If this is a known
> > issue then maybe someone can add info to the INTEL_IDLE help text
> > in the kernel configuration...
> Could be - without a serial crash it is hard to figure out.

Alright, I will enable INTEL_IDLE again so that I can report the crash
message. Won't be now but it will be within the next few days.

> Why do you want to use the intel idle driver? Can't you use
> the xen-acpi-processor driver which does the job of uploading
> the power management data to the hypervisor.
> (CONFIG_XEN_ACPI_PROCESSOR is the option you need to have enabled).

I just checked - I have enabled this option. It is in Device Drivers ->
Xen driver support which did confuse me somewhat, partially because the
rest of the ACPI options are under 'Power management and ACPI
options', also because the options look alike so much, I suppose
fatigue kicked in. :)

Anyway, It seems that CONFIG_XEN_ACPI_PROCESSOR depends on
ACPI_PROCESSOR, see below.

To answer your question about why I want to use the intel idle driver.
Actually I don't want/need to use it per se.. I simply thought it was
the logical choice to enable it in order to be able to use Intel
specific idle instructions.

> > I am using this on a dual CPU motherboard, it has two Xeon W3530
> > CPUs (i.e. family 6, model 26, stepping 5). I have also tested this
> > with a single-CPU Core2 Quad Q6600 and the same situation occurs
> > here, but the below output is of the W3530 Xeon system.
> > 
> > While I'm not that familiar with CPUidle, one thing that seems to be
> > not right is that the maximum idle state here is C3 while the
> > processor should be able to reach as far as C7.
> Right, it won't unless you don't compile acpi_pad
> your .config?

No, and this is where I start to wonder. I have built in the CPUFREQ
drivers and the kernel help text says that when this is the case,
CONFIG_XEN_ACPI_PROCESSOR must be Y as well. For this to work I have to

Depends on: XEN [=y] && X86 [=y] && ACPI_PROCESSOR [=y] && CPU_FREQ [=y]

The full .config is here:

What I am after: cpu scheduling (xenpm set-cpufreq-governor) and
maximum idle states. But you can see that I am not as knowledgable as
yourself, so further hints or requests for debugging are welcome (the
INTEL_IDLE boot crash message will be posted when I am able to fiddle
with the kernel again) and thanks so far for your answers.


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