Re: Workings/effectiveness of the xen-acpi-processor driver

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Tue, May 01, 2012 at 06:54:56PM -0400, Konrad Rzeszutek Wilk wrote:
> On Tue, May 01, 2012 at 06:35:45PM -0400, Boris Ostrovsky wrote:
> > On 05/01/2012 04:02 PM, Konrad Rzeszutek Wilk wrote:
> > >On Thu, Apr 26, 2012 at 06:25:28PM +0200, Stefan Bader wrote:
> > >>On 26.04.2012 17:50, Konrad Rzeszutek Wilk wrote:
> > >>>On Wed, Apr 25, 2012 at 03:00:58PM +0200, Stefan Bader wrote:
> > >>>>Since there have been requests about that driver to get backported into 3.2, I
> > >>>>was interested to find out what or how much would be gained by that.
> > >>>>
> > >>>>The first system I tried was an AMD based one (8 core Opteron 6128@2GHz). Which
> > >>>>was not very successful as the drivers bail out of the init function because the
> > >>>>first call to acpi_processor_register_performance() returns -ENODEV. There is
> > >>>>some frequency scaling when running without Xen, so I need to do some more
> > >>>>debugging there.
> > 
> > I believe this is caused by the somewhat under-enlightened xen_apic_read():
> > 
> > static u32 xen_apic_read(u32 reg)
> > {
> >         return 0;
> > }
> > 
> > This results in some data, most importantly
> > boot_cpu_physical_apicid, not being set correctly and, in turn,
> > causes x86_cpu_to_apicid to be broken.
> 
> What is the involvment of x86_cpu_to_apicid to acpi_processor_register_performance?
> Or is this more of a stab in the dark?

Ah, it is the acpi_get_cpuid that gets called by acpi_processor_add->acpi_processor_get_info.

And this one:
201 #ifdef CONFIG_SMP
202         for_each_possible_cpu(i) {
203                 if (cpu_physical_id(i) == apic_id)
204                         return i;
205         }               
206 #else   

where the cpu_physical_id(i) is per_cpu(x86_cpu_to_apicid, i).

But it is curious that it has been working for me on AMD and Intel machines.
Granted the only server boxes I've are Intel - don't have AMD server boxes at all.

Stefan, can you send the full dmesg output too please?