[Xen-devel] Failure to Parse and Load C-States

[Tom Goetz <thomas.goetz@xxxxxxxxxx>]

Konrad,

We're seeing a failure where c-states are not parsed and loaded to the 
hypervisor.

What is happening is when the following calls happen, there are no c-states in 
the per CPU data.

[    1.954368]  [<ffffffff8157840e>] push_cxx_to_hypervisor+0x1a5/0x2d5
[    1.954374]  [<ffffffff815785ab>] upload_pm_data+0x6d/0xa2
[    1.954380]  [<ffffffff81afe101>] xen_acpi_processor_init+0x3c3/0x488

It looks like the c-state parsing should have happened in 
acpi_processor_power_init but didn't because of the following check at the top:

        if (disabled_by_idle_boot_param())
                return 0;

The preceding is true because boot_option_idle_override is set to IDLE_HALT by 
arch/x86/xen/setup.c xen_arch_setup.

Is the Xen version of acpi_processor supposed to do it's own c-state parsing or 
rely on the base acpi_processor c-state parsing? I'm assuming Xen sets 
IDLE_HALT to stop runtime usage of Linux c-state management, but it also stops 
parsing c-states.

Linux: 3.2.23
Xen: 4.0.4

Thanks for any help,

Tom Goetz
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