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authorYazen Ghannam <yazen.ghannam@amd.com>2018-04-03 09:02:28 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-05-01 12:58:26 -0700
commitb319531024d9b3c4d63965efc92d8e04803f42ce (patch)
parentce911a5b1fea9700f797c3bd5dc9d9d94c996ac3 (diff)
x86/smpboot: Don't use mwait_play_dead() on AMD systems
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: 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 2651ca2112c4..6b841262b790 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1613,6 +1613,8 @@ 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))
if (!this_cpu_has(X86_FEATURE_CLFLUSH))