On 06.02.2025 09:32, Penny Zheng wrote:
> --- a/docs/misc/xen-command-line.pandoc
> +++ b/docs/misc/xen-command-line.pandoc
> @@ -515,7 +515,7 @@ If set, force use of the performance counters for
> oprofile, rather than detectin
> available support.
>
> ### cpufreq
> -> `= none | {{ <boolean> | xen } {
> [:[powersave|performance|ondemand|userspace][,[<maxfreq>]][,[<minfreq>]]] }
> [,verbose]} | dom0-kernel | hwp[:[<hdc>][,verbose]] | amd-cppc[:[verbose]]`
> +> `= none | {{ <boolean> | xen } {
> [:[powersave|performance|ondemand|userspace][,[<maxfreq>]][,[<minfreq>]]] }
> [,verbose]} | dom0-kernel | hwp[:[<hdc>][,verbose]] |
> amd-cppc[:[active][,verbose]]`
>
> > Default: `xen`
>
> @@ -538,6 +538,12 @@ choice of `dom0-kernel` is deprecated and not supported
> by all Dom0 kernels.
> on supported AMD hardware to provide finer grained frequency control
> mechanism.
> The default is disabled. If `amd-cppc` is selected, but hardware support
> is not available, Xen will fallback to cpufreq=xen.
> +* `active` is a boolean to enable amd-cppc driver in active(autonomous) mode.
> + In this mode, users could provide a hint with energy performance preference
> + register to the hardware if they want to bias toward performance(0x0) or
> + energy efficiency(0xff), then CPPC power algorithm will calculate the
> runtime
> + workload and adjust the realtime cores frequency according to the power
> supply
> + and thermal, core voltage and some other hardware conditions.
All the option offers to the user is a boolean. The description wants to be
written based on that; to be honest, with what is there and with the new
variable not actually consumed anywhere, I have no real idea what this is
about. Hex numbers in particular don't belong here at all, imo. And "users
could provide a hint" needs to be more practical: Users don't directly write
to the "energy performance preference register" (or any other one).
> --- a/xen/arch/x86/acpi/cpufreq/amd-cppc.c
> +++ b/xen/arch/x86/acpi/cpufreq/amd-cppc.c
> @@ -33,6 +33,8 @@
> #define amd_cppc_warn(fmt, args...) \
> printk(XENLOG_WARNING "AMD_CPPC: CPU%u warning: " fmt, cpu, ## args)
>
> +static bool __ro_after_init opt_cpufreq_active;
The name is ambiguous. It reads as if this was a global enable/disable for
the cpufreq subsystem. opt_active_mode perhaps, seeing this is local to
the CPPC driver?
Jan
