Re: coretemp driver change on dual-die/package systems

[Zhang Rui <rui.zhang@intel.com>]

On 一, 2019-02-11 at 06:13 -0800, Guenter Roeck wrote:
> On 2/11/19 1:46 AM, Zhang Rui wrote:
> > 
> > Hi, Jean and Guenter,
> > 
> > Per the Intel Software Developer's Manual, which you can found at
> > www.i
> > ntel.com/sdm, when CPUID.1F is present, it is preferred over
> > CPUID.B.
> > 
> > New dual-die/package systems will see this difference:
> >     CPUID.0B enumerates the CPUs on each die as if they were in
> > different packages.
> >     CPUID.1F enumerates the CPUs on each die within the same
> > package.
> > 
> > This will manifest in the sysfs physical_package_id attribute. ie.
> > In
> > the example above, CPUID.B would cause lscpu to show 2 packages,
> > and
> > CPUID.1F will cause lscpu to show 1 package.
> > 
> > Also, with CPUID.B the concept of a package-scope MSR and a die-
> > scope
> > MSR are synonymous.  With CPUID.1F, it is possible for some MSRs to
> > have die-scope, and other MSRs to have package-scope.
> > 
> > MSR_IA32_PACKAGE_THERM_STATUS is a die-scope MSR, thus we need to
> > update the coretemp driver to become multi-die-aware when we
> > support
> > CPUID.1F.
> > 
> > Previously, we create one hwmon device for each package, now we
> > need to
> > create one hwmon device for each die.
> > But there is one problem left. For each coretemp hwmon device, the
> > "temp1_input" attribute represents the temperature got from
> > MSR_IA32_PACKAGE_THERM_STATUS, and "temp1_label" is "Package id X",
> > where X is the logical package id.
> > Now we create one hwmon device for each die, thus temp1_label can
> > not
> > use logical package id any more, because there are two dies in the
> > same
> > package.
> > To me, there are two choices,
> > 1. changing "temp1_label" from "Package id X" to "Package id Y",
> > where
> > Y is just a unique number instead of logical package id, say, using
> > ida.
> > 2. changing "temp1_label" from "Package id X" to "Package id X Die
> > id
> > Y", where Y is the die id.
> > 
> > Question is I'm not sure how temp1_label is used and if this change
> > will break any userspace, like lm-sensors?
> > 
> Please feel free to change the label as it makes sense. I would
> suggest option
> 2 to avoid confusion. The string it reports is not part of the ABI
> and
> can be changed. It can be overwritten with sensors3.conf anyway, so
> nothing
> should depend on it.

Good to know. Thanks for the clarification, Guenter!

-rui

> 
> Guenter