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RE: [PATCH v4 05/15] xen/x86: introduce "cpufreq=amd-cppc" xen cmdline
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: "Penny, Zheng" <penny.zheng@xxxxxxx>
- Date: Mon, 19 May 2025 08:36:44 +0000
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- Cc: "Huang, Ray" <Ray.Huang@xxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, "Orzel, Michal" <Michal.Orzel@xxxxxxx>, Julien Grall <julien@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Mon, 19 May 2025 08:37:12 +0000
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- Thread-topic: [PATCH v4 05/15] xen/x86: introduce "cpufreq=amd-cppc" xen cmdline
[Public]
> -----Original Message-----
> From: Jan Beulich <jbeulich@xxxxxxxx>
> Sent: Tuesday, April 29, 2025 8:52 PM
> To: Penny, Zheng <penny.zheng@xxxxxxx>
> Cc: Huang, Ray <Ray.Huang@xxxxxxx>; Andrew Cooper
> <andrew.cooper3@xxxxxxxxxx>; Anthony PERARD <anthony.perard@xxxxxxxxxx>;
> Orzel, Michal <Michal.Orzel@xxxxxxx>; Julien Grall <julien@xxxxxxx>; Roger Pau
> Monné <roger.pau@xxxxxxxxxx>; Stefano Stabellini <sstabellini@xxxxxxxxxx>;
> xen-
> devel@xxxxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH v4 05/15] xen/x86: introduce "cpufreq=amd-cppc" xen
> cmdline
>
> On 14.04.2025 09:40, Penny Zheng wrote:
> > --- a/xen/include/acpi/cpufreq/processor_perf.h
> > +++ b/xen/include/acpi/cpufreq/processor_perf.h
> > @@ -5,6 +5,9 @@
> > #include <public/sysctl.h>
> > #include <xen/acpi.h>
> >
> > +/* ability bits */
> > +#define XEN_PROCESSOR_PM_CPPC 8
>
> This needs correlating (at least via commentary, better by build-time
> checking) with
> the other XEN_PROCESSOR_PM_* values. Otherwise someone adding a new
> #define in the public header may not (easily) notice a possible conflict.
> With that in
> mind I also question whether 8 is actually a good choice: That's the obvious
> next
> value to use in the public interface. SIF_PM_MASK is 8 bits wide, so a
> sensible
> value to use here would by e.g. 0x100.
>
I've added a public flag anchor "XEN_PROCESSOR_PM_PUBLIC_END" in public header:
#define XEN_PROCESSOR_PM_PUBLIC_END XEN_PROCESSOR_PM_TX
and will do the following build-time checking:
BUILD_BUG_ON(XEN_PROCESSOR_PM_CPPC <= XEN_PROCESSOR_PM_PUBLIC_END);
> Jan
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