This patch assumes that if a package state is disabled, the corresponding core state must be disabled. That assumption is false. Indeed, that is a very popular and useful configuration.
But even if that were not the case, this software is not necessary, since the hardware handles demotion "c-state clipping" automatically. Yes, there is a case where a certain version of a certain processor has broken demotion, but this isn't the right fix for that. The right fix for that is here: https://bugzilla.kernel.org/show_bug.cgi?id=109081 and will be upstream shortly. thanks, -Len On Mon, Mar 21, 2016 at 8:49 AM, Prarit Bhargava <pra...@redhat.com> wrote: > Some Intel processors have cstates limited by MSR_PKG_CST_CONFIG_CONTROL > (0xE2), which specifies the lowest processor-specific C-state code name > (consuming the least power). The intel_idle driver does not query this MSR to > see if states are limited by hardware. In the case of the i7-6700HQ the value > of bits 3:0 on the MSR are 0x6, meaning that C9-SKL (0x7) and C10-SKL (0x8) > should have been disabled. > > This patch adds a limit field to the cpuidle_state struct to hold the > cstate encodings for each processor, and queries the values the values > to confirm support. > > After applying this patchset the system now boots and reports that > some states have been disabled: > > [root@dhcp40-125 ~]# dmesg | grep intel_idle > [ 1.163367] intel_idle: MWAIT substates: 0x11142120 > [ 1.163368] intel_idle: v0.4 model 0x5E > [ 1.163369] intel_idle: lapic_timer_reliable_states 0xffffffff > [ 1.163370] intel_idle: state C9-SKL (0x7) is disabled. Max Package limit > is 0x6. > [ 1.163371] intel_idle: state C10-SKL (0x8) is disabled. Max Package > limit is 0x6. > > Cc: x...@kernel.org > Cc: Len Brown <l...@kernel.org> > Cc: "Peter Zijlstra (Intel)" <pet...@infradead.org> > Cc: Borislav Petkov <b...@suse.de> > Cc: Andi Kleen <a...@linux.intel.com> > Cc: Alexander Shishkin <alexander.shish...@linux.intel.com> > Cc: Dasaratharaman Chandramouli <dasaratharaman.chandramo...@intel.com> > Cc: linux...@vger.kernel.org > Signed-off-by: Prarit Bhargava <pra...@redhat.com> > > Prarit Bhargava (3): > idle, rename MSR_NHM_SNB_PKG_CST_CFG_CTL to > MSR_PKG_CST_CONFIG_CONTROL > intel_idle, Introduce cstate limits and fix hardware cstate disable > value > cpuidle, Prevent users from enabling cstates that are disabled in > Hardware > > arch/x86/include/asm/msr-index.h | 2 +- > drivers/cpuidle/governors/ladder.c | 3 ++ > drivers/cpuidle/governors/menu.c | 4 ++ > drivers/cpuidle/sysfs.c | 34 +++++++++++- > drivers/idle/intel_idle.c | 93 > ++++++++++++++++++++++++++++++++- > include/linux/cpuidle.h | 11 +++- > tools/power/x86/turbostat/turbostat.8 | 2 +- > tools/power/x86/turbostat/turbostat.c | 10 ++-- > 8 files changed, 146 insertions(+), 13 deletions(-) > > -- > 1.7.9.3 > -- Len Brown, Intel Open Source Technology Center
