Re: [Xen-devel] Linux 3.4 dom0 kernel error loading xen-acpi-processor: Input/output error

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Mar 07, 2013 at 09:48:08AM +0200, Pasi Kärkkäinen wrote:
> On Wed, Mar 06, 2013 at 07:29:34PM -0500, Konrad Rzeszutek Wilk wrote:
> > > > 
> > > > Actually the correct path is: /sys/firmware/acpi/tables/DSDT
> > > > So the acpi tables are there.
> > > > 
> > > > .. but the problem is there's no _PCT info in them.
> > > > 
> > > 
> > > .. so on which hardware is xen-acpi-processor driver required? 
> > > 
> > > Is the actual problem that I don't have _PCT because it's not 
> > > required/supported on my hw,
> > > and thus I don't need the whole xen-acpi-processor driver? 
> > > 
> > > I checked the Xeon 5600 CPU, and also Ivy Bridge i7, and there's no _PCT 
> > > on either one..
> > 
> > I always forget which of _P* are important. I think _PPC, _PSS and _PCD
> > are the crucial ones. The _PCT is the thermal one - which I think are 
> > usually
> > found on laptops.
> > 
> 
> I don't seem to have _PCT on my Ivy Bridge i7 laptop.. 
> 
> > In your case then .. lets go back to the start - the driver failed with -EIO
> > and it was v3.4.x kernel? Now that I've figured out the regression with v3.9
> > I can take a look at this.
> > 
> 
> Ok.
> 
> So the problem for me with Linux 3.4.32 kernel is "modprobe 
> xen-acpi-processor" fails:
> initcall xen_acpi_processor_init+0x0/0x6b0 [xen_acpi_processor] returned with 
> error code -5
> 

Great :-( On my box (SandyBridge i3 2100, MS-7680) it installs just fine. This 
is
v3.4.22 with 

cat linux-build/.config|grep PROCESSOR
CONFIG_ACPI_PROCESSOR=y
CONFIG_ACPI_PROCESSOR_AGGREGATOR=m
CONFIG_XEN_ACPI_PROCESSOR=m


> The error deeper down in the ACPI internals is:
> processor_perflib-0430 [00] processor_get_performa: ACPI-based processor 
> performance control unavailable

I think looking at the code, that even on baremetal you would not have
any P-states.

I am looking at the code, and the one thing that caught my eye is this comment:

/*
 * Do a quick check if the systems looks like it should use ACPI
 * cpufreq. We look at a _PCT method being available, but don't
 * do a whole lot of sanity checks.
 */

And since your machine has no _PCT, it just bypasses it.

Is there a BIOS option for power saving? Perhaps its off? 
> 
> Function call path is this:
> 
> xen_acpi_processor_init()
>       acpi_processor_register_performance(perf, i)                    <-- 
> returns -EIO
>               acpi_processor_get_performance_info(pr)                 <-- 
> returns -ENODEV and prints the error to dmesg
>                       acpi_get_handle(pr->handle, "_PCT", &handle);   
>                               acpi_ns_get_node()                      <-- 
> doesn't find _PCT
> 
>       goto err_out;                                                   <-- 
> modprobe xen-acpi-processor fails
> 
> 
> The CPU in question is:
> Intel(R) Xeon(R) CPU L5640
> 
> ACPI DSDT.dsl is here:
> http://pasik.reaktio.net/dell-r510-acpi-dsdt.dsl

Oh wait, this is not an laptop! It is some rack-server.

> 
> -- Pasi
> 
> 
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> 

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