On 20.05.2025 10:28, Penny, Zheng wrote: > [Public] > >> -----Original Message----- >> From: Jan Beulich <jbeul...@suse.com> >> Sent: Monday, May 19, 2025 9:19 PM >> To: Penny, Zheng <penny.zh...@amd.com> >> Cc: Huang, Ray <ray.hu...@amd.com>; Andrew Cooper >> <andrew.coop...@citrix.com>; Anthony PERARD <anthony.per...@vates.tech>; >> Orzel, Michal <michal.or...@amd.com>; Julien Grall <jul...@xen.org>; Roger >> Pau >> Monné <roger....@citrix.com>; Stefano Stabellini <sstabell...@kernel.org>; >> xen- >> de...@lists.xenproject.org >> Subject: Re: [PATCH v4 05/15] xen/x86: introduce "cpufreq=amd-cppc" xen >> cmdline >> >> On 19.05.2025 10:36, Penny, Zheng wrote: >>> [Public] >>> >>>> -----Original Message----- >>>> From: Jan Beulich <jbeul...@suse.com> >>>> Sent: Tuesday, April 29, 2025 8:52 PM >>>> To: Penny, Zheng <penny.zh...@amd.com> >>>> Cc: Huang, Ray <ray.hu...@amd.com>; Andrew Cooper >>>> <andrew.coop...@citrix.com>; Anthony PERARD >>>> <anthony.per...@vates.tech>; Orzel, Michal <michal.or...@amd.com>; >>>> Julien Grall <jul...@xen.org>; Roger Pau Monné >>>> <roger....@citrix.com>; Stefano Stabellini <sstabell...@kernel.org>; >>>> xen- de...@lists.xenproject.org >>>> 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); >> >> I don't really see why anything would need to be added to the public header >> (and we >> really should strive to avoid unnecessary additions). > > If I put such definition > "#define XEN_PROCESSOR_PM_PUBLIC_END XEN_PROCESSOR_PM_TX" > in internal header, I'm afraid it won't be updated if new ones added in the > public in the future. > Or any other suggestions to provide build-time checking?
Imo it's sufficient to check that the new #define doesn't overlap with SIF_PM_MASK. Jan
