From: Yazen Ghannam Date: Tue, 3 Apr 2018 09:02:28 -0500 Subject: x86/smpboot: Don't use mwait_play_dead() on AMD systems Git-commit: da6fa7ef67f07108a1b0cb9fd9e7fcaabd39c051 Patch-mainline: v4.17-rc3 References: bsc#1110006 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 Signed-off-by: Thomas Gleixner Reviewed-by: Borislav Petkov Cc: stable@vger.kernel.org Cc: Yazen Ghannam Link: https://lkml.kernel.org/r/20180403140228.58540-1-Yazen.Ghannam@amd.com Acked-by: Joerg Roedel --- arch/x86/kernel/smpboot.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 45175b81dd5b..0f1cbb042f49 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1571,6 +1571,8 @@ 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))