3.16.60-rc1 review patch. If anyone has any objections, please let me know.
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From: Yazen Ghannam yazen.ghannam@amd.com
commit da6fa7ef67f07108a1b0cb9fd9e7fcaabd39c051 upstream.
Recent AMD systems support using MWAIT for C1 state. However, MWAIT will not allow deeper cstates than C1 on current systems.
play_dead() expects to use the deepest state available. The deepest state available on AMD systems is reached through SystemIO or HALT. If MWAIT is available, it is preferred over the other methods, so the CPU never reaches the deepest possible state.
Don't try to use MWAIT to play_dead() on AMD systems. Instead, use CPUIDLE to enter the deepest state advertised by firmware. If CPUIDLE is not available then fallback to HALT.
Signed-off-by: Yazen Ghannam yazen.ghannam@amd.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Reviewed-by: Borislav Petkov bp@suse.de Cc: Yazen Ghannam Yazen.Ghannam@amd.com Link: https://lkml.kernel.org/r/20180403140228.58540-1-Yazen.Ghannam@amd.com Signed-off-by: Ben Hutchings ben@decadent.org.uk --- arch/x86/kernel/smpboot.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1397,6 +1397,8 @@ static inline void mwait_play_dead(void) void *mwait_ptr; int i;
+ if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) + return; if (!this_cpu_has(X86_FEATURE_MWAIT)) return; if (!this_cpu_has(X86_FEATURE_CLFLUSH))