Messages in this thread Patch in this message |  | | From | Yazen Ghannam <> | Subject | [PATCH] x86/smpboot: Don't do mwait_play_dead() on AMD systems | Date | Mon, 2 Apr 2018 13:34:24 -0500 |
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From: Yazen Ghannam <yazen.ghannam@amd.com>
Recent AMD systems support using MWAIT for C1 state. However, MWAIT will not allow deeper cstates than C1 on current systems.
With play_dead() we expect the OS to use the deepest state available. The deepest state available on AMD systems is reached through SystemIO or HALT. If MWAIT is available, we use it instead of the other methods, so we never reach the deepest state.
Don't try to use MWAIT to play_dead() on AMD systems. Instead, we'll use CPUIDLE to enter the deepest state advertised by firmware. If CPUIDLE is not available then we fallback to HALT.
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com> --- arch/x86/kernel/smpboot.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index ff99e2b6fc54..67cf00b25f83 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1536,6 +1536,9 @@ static inline void mwait_play_dead(void) void *mwait_ptr; int i; + /* Don't try native MWAIT on AMD. Stick to CPUIDLE and HALT. */ + 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)) -- 2.14.1
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