Hi, Laurent, I ran into a boot hang regression with latest upstream code, and it took me a while to bisect the offending commit and workaround it. Now I have tested this patch series on an Intel RaptorLake Hybrid platform (4 Pcores with HT and 4 Ecores without HT), and it works as expected. So, for patch 1~7 in this series, Tested-by: Zhang Rui <rui.zhang@xxxxxxxxx> thanks, rui On Wed, 2023-07-05 at 16:51 +0200, Laurent Dufour wrote: > I'm taking over the series Michael sent previously [1] which is > smartly > reviewing the initial series I sent [2]. This series is addressing > the > comments sent by Thomas and me on the Michael's one. > > Here is a short introduction to the issue this series is addressing: > > When a new CPU is added, the kernel is activating all its threads. > This > leads to weird, but functional, result when adding CPU on a SMT 4 > system > for instance. > > Here the newly added CPU 1 has 8 threads while the other one has 4 > threads > active (system has been booted with the 'smt-enabled=4' kernel > option): > > ltcden3-lp12:~ # ppc64_cpu --info > Core 0: 0* 1* 2* 3* 4 5 6 7 > Core 1: 8* 9* 10* 11* 12* 13* 14* 15* > > This mixed SMT level may confused end users and/or some applications. > > There is no SMT level recorded in the kernel (common code), neither > in user > space, as far as I know. Such a level is helpful when adding new CPU > or > when optimizing the energy efficiency (when reactivating CPUs). > > When SMP and HOTPLUG_SMT are defined, this series is adding a new SMT > level > (cpu_smt_num_threads) and few callbacks allowing the architecture > code to > fine control this value, setting a max and a "at boot" level, and > controling whether a thread should be onlined or not. > > v4: > Rebase on top of 6.5's updates > Remove a dependancy against the X86's symbol > cpu_primary_thread_mask > v3: > Fix a build error in the patch 6/9 > v2: > As Thomas suggested, > Reword some commit's description > Remove topology_smt_supported() > Remove topology_smt_threads_supported() > Introduce CONFIG_SMT_NUM_THREADS_DYNAMIC > Remove switch() in __store_smt_control() > Update kernel-parameters.txt > > [1] > https://lore.kernel.org/linuxppc-dev/20230524155630.794584-1-mpe@xxxxxxxxxxxxxx/ > [2] > https://lore.kernel.org/linuxppc-dev/20230331153905.31698-1-ldufour@xxxxxxxxxxxxx/ > > > Laurent Dufour (2): > cpu/hotplug: remove dependancy against cpu_primary_thread_mask > cpu/SMT: Remove topology_smt_supported() > > Michael Ellerman (8): > cpu/SMT: Move SMT prototypes into cpu_smt.h > cpu/SMT: Move smt/control simple exit cases earlier > cpu/SMT: Store the current/max number of threads > cpu/SMT: Create topology_smt_thread_allowed() > cpu/SMT: Allow enabling partial SMT states via sysfs > powerpc/pseries: Initialise CPU hotplug callbacks earlier > powerpc: Add HOTPLUG_SMT support > powerpc/pseries: Honour current SMT state when DLPAR onlining CPUs > > .../ABI/testing/sysfs-devices-system-cpu | 1 + > .../admin-guide/kernel-parameters.txt | 4 +- > arch/Kconfig | 3 + > arch/powerpc/Kconfig | 2 + > arch/powerpc/include/asm/topology.h | 15 ++ > arch/powerpc/kernel/smp.c | 8 +- > arch/powerpc/platforms/pseries/hotplug-cpu.c | 30 ++-- > arch/powerpc/platforms/pseries/pseries.h | 2 + > arch/powerpc/platforms/pseries/setup.c | 2 + > arch/x86/include/asm/topology.h | 4 +- > arch/x86/kernel/cpu/common.c | 2 +- > arch/x86/kernel/smpboot.c | 8 - > include/linux/cpu.h | 25 +-- > include/linux/cpu_smt.h | 33 ++++ > kernel/cpu.c | 142 +++++++++++++--- > -- > 15 files changed, 196 insertions(+), 85 deletions(-) > create mode 100644 include/linux/cpu_smt.h >
