From 23ccee22e834eca236b9a20989caf6905bd6954a Mon Sep 17 00:00:00 2001 From: Giovanni Gherdovich Date: Thu, 16 Apr 2020 07:47:43 +0200 Subject: [PATCH] x86, sched: Account for CPUs with less than 4 cores in freq. invariance If a CPU has less than 4 physical cores, MSR_TURBO_RATIO_LIMIT will rightfully report that the 4C turbo ratio is zero. In such cases, use the 1C turbo ratio instead for frequency invariance calculations. Fixes: 1567c3e3467c ("x86, sched: Add support for frequency invariance") Reported-by: Like Xu Reported-by: Neil Rickert Signed-off-by: Giovanni Gherdovich Signed-off-by: Peter Zijlstra (Intel) Acked-by: Rafael J. Wysocki Tested-by: Dave Kleikamp Link: https://lkml.kernel.org/r/20200416054745.740-3-ggherdovich@suse.cz --- arch/x86/kernel/smpboot.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 3a318ec..5d346b7 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1945,18 +1945,23 @@ static bool skx_set_max_freq_ratio(u64 *base_freq, u64 *turbo_freq, int size) static bool core_set_max_freq_ratio(u64 *base_freq, u64 *turbo_freq) { + u64 msr; int err; err = rdmsrl_safe(MSR_PLATFORM_INFO, base_freq); if (err) return false; - err = rdmsrl_safe(MSR_TURBO_RATIO_LIMIT, turbo_freq); + err = rdmsrl_safe(MSR_TURBO_RATIO_LIMIT, &msr); if (err) return false; - *base_freq = (*base_freq >> 8) & 0xFF; /* max P state */ - *turbo_freq = (*turbo_freq >> 24) & 0xFF; /* 4C turbo */ + *base_freq = (*base_freq >> 8) & 0xFF; /* max P state */ + *turbo_freq = (msr >> 24) & 0xFF; /* 4C turbo */ + + /* The CPU may have less than 4 cores */ + if (!*turbo_freq) + *turbo_freq = msr & 0xFF; /* 1C turbo */ return true; } -- 2.7.4