mainline inclusion from mainline-5.2 commit 987ddbe4870b53623d76ac64044c55a13e368113 category: x86/power

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For new Centaur CPUs the ucode will take care of the preservation of cache coherence between CPU cores in C-states regardless of how deep the C-states are. So, it is not necessary to flush the caches in software befor entering C3. This useless operation will cause performance drop for the cores which share some caches with the idling core.

Signed-off-by: David Wang davidwang@zhaoxin.com Reviewed-by: Thomas Gleixner tglx@linutronix.de Acked-by: Pavel Machek pavel@ucw.cz Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: brucechang@via-alliance.com Cc: cooperyan@zhaoxin.com Cc: len.brown@intel.com Cc: linux-pm@kernel.org Cc: qiyuanwang@zhaoxin.com Cc: rjw@rjwysocki.net Cc: timguo@zhaoxin.com Link: http://lkml.kernel.org/r/1545900110-2757-1-git-send-email-davidwang@zhaoxin.... [ Tidy up the comment. ] Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: LeoLiu-oc LeoLiu-oc@zhaoxin.com --- arch/x86/kernel/acpi/cstate.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)

diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c index 92539a1c3e31..45745ecaa624 100644 --- a/arch/x86/kernel/acpi/cstate.c +++ b/arch/x86/kernel/acpi/cstate.c @@ -51,6 +51,18 @@ void acpi_processor_power_init_bm_check(struct acpi_processor_flags *flags, if (c->x86_vendor == X86_VENDOR_INTEL && (c->x86 > 0xf || (c->x86 == 6 && c->x86_model >= 0x0f))) flags->bm_control = 0; + /* + * For all recent Centaur CPUs, the ucode will make sure that each + * core can keep cache coherence with each other while entering C3 + * type state. So, set bm_check to 1 to indicate that the kernel + * doesn't need to execute a cache flush operation (WBINVD) when + * entering C3 type state. + */ + if (c->x86_vendor == X86_VENDOR_CENTAUR) { + if (c->x86 > 6 || (c->x86 == 6 && c->x86_model == 0x0f && + c->x86_stepping >= 0x0e)) + flags->bm_check = 1; + } } EXPORT_SYMBOL(acpi_processor_power_init_bm_check);