The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 9c7d9017a49fb8516c13b7bff59b7da2abed23e1 Mon Sep 17 00:00:00 2001
From: "Rafael J. Wysocki" rafael.j.wysocki@intel.com Date: Fri, 8 Jan 2021 19:05:59 +0100 Subject: [PATCH] x86: PM: Register syscore_ops for scale invariance
On x86 scale invariace tends to be disabled during resume from suspend-to-RAM, because the MPERF or APERF MSR values are not as expected then due to updates taking place after the platform firmware has been invoked to complete the suspend transition.
That, of course, is not desirable, especially if the schedutil scaling governor is in use, because the lack of scale invariance causes it to be less reliable.
To counter that effect, modify init_freq_invariance() to register a syscore_ops object for scale invariance with the ->resume callback pointing to init_counter_refs() which will run on the CPU starting the resume transition (the other CPUs will be taken care of the "online" operations taking place later).
Fixes: e2b0d619b400 ("x86, sched: check for counters overflow in frequency invariant accounting") Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Acked-by: Giovanni Gherdovich ggherdovich@suse.cz Link: https://lkml.kernel.org/r/1803209.Mvru99baaF@kreacher
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 8ca66af96a54..117e24fbfd8a 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -56,6 +56,7 @@ #include <linux/numa.h> #include <linux/pgtable.h> #include <linux/overflow.h> +#include <linux/syscore_ops.h>
#include <asm/acpi.h> #include <asm/desc.h> @@ -2083,6 +2084,23 @@ static void init_counter_refs(void) this_cpu_write(arch_prev_mperf, mperf); }
+#ifdef CONFIG_PM_SLEEP +static struct syscore_ops freq_invariance_syscore_ops = { + .resume = init_counter_refs, +}; + +static void register_freq_invariance_syscore_ops(void) +{ + /* Bail out if registered already. */ + if (freq_invariance_syscore_ops.node.prev) + return; + + register_syscore_ops(&freq_invariance_syscore_ops); +} +#else +static inline void register_freq_invariance_syscore_ops(void) {} +#endif + static void init_freq_invariance(bool secondary, bool cppc_ready) { bool ret = false; @@ -2109,6 +2127,7 @@ static void init_freq_invariance(bool secondary, bool cppc_ready) if (ret) { init_counter_refs(); static_branch_enable(&arch_scale_freq_key); + register_freq_invariance_syscore_ops(); pr_info("Estimated ratio of average max frequency by base frequency (times 1024): %llu\n", arch_max_freq_ratio); } else { pr_debug("Couldn't determine max cpu frequency, necessary for scale-invariant accounting.\n");