From: Yazen Ghannam <yazen.ghannam@amd.com>
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 <yazen.ghannam@amd.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: stable@vger.kernel.org
Cc: Yazen Ghannam <Yazen.Ghannam@amd.com>
Link: https://lkml.kernel.org/r/20180403140228.58540-1-Yazen.Ghannam@amd.com

Acked-by: Joerg Roedel <jroedel@suse.de>
---
 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))