x86/smpboot: Don't use mwait_play_dead() on AMD systems

[ Upstream commit da6fa7ef67f07108a1b0cb9fd9e7fcaabd39c051 ]

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
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index f6911cc90a815e63c74663f94d5cb2cc5d9c2ca1..a92919864e044655d2dd75a026c5e0aa8e3995ea 100644 (file)
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1400,6 +1400,8 @@ 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))