[Public] > -----Original Message----- > From: Jan Beulich <jbeul...@suse.com> > Sent: Thursday, August 28, 2025 8:10 PM > To: Penny, Zheng <penny.zh...@amd.com> > Cc: Huang, Ray <ray.hu...@amd.com>; Andrew Cooper > <andrew.coop...@citrix.com>; Roger Pau Monné <roger....@citrix.com>; > Anthony PERARD <anthony.per...@vates.tech>; Orzel, Michal > <michal.or...@amd.com>; Julien Grall <jul...@xen.org>; Stefano Stabellini > <sstabell...@kernel.org>; Juergen Gross <jgr...@suse.com>; xen- > de...@lists.xenproject.org > Subject: Re: [PATCH v8 0/8] amd-cppc CPU Performance Scaling Driver > > On 28.08.2025 12:02, Penny Zheng wrote: > > amd-cppc is the AMD CPU performance scaling driver that introduces a > > new CPU frequency control mechanism on modern AMD APU and CPU series > > in Xen. The new mechanism is based on Collaborative Processor > > Performance Control (CPPC) which provides finer grain frequency > > management than legacy ACPI hardware P-States. Current AMD CPU/APU > > platforms are using the ACPI P-states driver to manage CPU frequency > > and clocks with switching only in 3 P-states. CPPC replaces the ACPI > > P-states controls and allows a flexible, low-latency interface for Xen > > to directly communicate the performance hints to hardware. > > > > amd_cppc driver has 2 operation modes: autonomous (active) mode, and > > non-autonomous (passive) mode. We register different CPUFreq driver > > for different modes, "amd-cppc" for passive mode and "amd-cppc-epp" > > for active mode. > > > > The passive mode leverages common governors such as *ondemand*, > > *performance*, etc, to manage the performance tuning. While the active > > mode uses epp to provides a hint to the hardware if software wants to > > bias toward performance (0x0) or energy efficiency (0xff). CPPC power > > algorithm in hardware will automatically calculate the runtime > > workload and adjust the realtime cpu cores frequency according to the > > power supply and thermal, core voltage and some other hardware conditions. > > > > amd-cppc is enabled on passive mode with a top-level > > `cpufreq=amd-cppc` option, while users add extra `active` flag to select > > active > mode. > > > > With `cpufreq=amd-cppc,active`, we did a 60s sampling test to see the > > CPU frequency change, through tweaking the energy_perf preference from > > `xenpm set-cpufreq-cppc powersave` to `xenpm set-cpufreq-cppc performance`. > > The outputs are as follows: > > ``` > > Setting CPU in powersave mode > > Sampling and Outputs: > > Avg freq 580000 KHz > > Avg freq 580000 KHz > > Avg freq 580000 KHz > > Setting CPU in performance mode > > Sampling and Outputs: > > Avg freq 4640000 KHz > > Avg freq 4220000 KHz > > Avg freq 4640000 KHz > > ``` > > > > Penny Zheng (8): > > xen/cpufreq: introduce new sub-hypercall to propagate CPPC data > > xen/cpufreq: introduce "cpufreq=amd-cppc" xen cmdline and amd-cppc > > driver > > xen/cpufreq: implement amd-cppc driver for CPPC in passive mode > > xen/cpufreq: implement amd-cppc-epp driver for CPPC in active mode > > xen/cpufreq: get performance policy from governor set via xenpm > > tools/cpufreq: extract CPPC para from cpufreq para > > xen/cpufreq: bypass governor-related para for amd-cppc-epp > > xen/cpufreq: Adapt SET/GET_CPUFREQ_CPPC xen_sysctl_pm_op for amd- > cppc > > driver > > > > docs/misc/xen-command-line.pandoc | 14 +- > > tools/include/xenctrl.h | 3 +- > > tools/libs/ctrl/xc_pm.c | 25 +- > > tools/misc/xenpm.c | 94 ++- > > xen/arch/x86/acpi/cpufreq/Makefile | 1 + > > xen/arch/x86/acpi/cpufreq/amd-cppc.c | 766 ++++++++++++++++++++++ > > xen/arch/x86/acpi/cpufreq/cpufreq.c | 69 +- > > xen/arch/x86/cpu/amd.c | 8 +- > > xen/arch/x86/include/asm/amd.h | 2 + > > xen/arch/x86/include/asm/msr-index.h | 6 + > > xen/arch/x86/platform_hypercall.c | 19 + > > xen/arch/x86/x86_64/cpufreq.c | 19 + > > xen/arch/x86/x86_64/platform_hypercall.c | 3 + > > xen/drivers/acpi/pm-op.c | 68 +- > > xen/drivers/acpi/pmstat.c | 4 + > > xen/drivers/cpufreq/cpufreq.c | 137 +++- > > xen/drivers/cpufreq/utility.c | 15 + > > xen/include/acpi/cpufreq/cpufreq.h | 40 +- > > xen/include/acpi/cpufreq/processor_perf.h | 14 +- > > xen/include/public/platform.h | 26 + > > xen/include/public/sysctl.h | 5 +- > > xen/include/xen/pmstat.h | 5 + > > xen/include/xlat.lst | 1 + > > 23 files changed, 1283 insertions(+), 61 deletions(-) create mode > > 100644 xen/arch/x86/acpi/cpufreq/amd-cppc.c > > Oh, and - what is still missing is a CHANGELOG.md entry.
Thx, understood. > > Jan
