If 'idle=nomwait' is specified or process matching what's in
processor_idle_dmi_table, we should't use MWAIT at bootup stage before
cpuidle driver loaded, even if it's preferred by default on Intel.

Add a check so that HALT instruction is used in those cases.

Signed-off-by: Zhenzhong Duan <zhenzhong.d...@oracle.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Borislav Petkov <b...@alien8.de>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: "H. Peter Anvin" <h...@zytor.com>
Cc: Boris Ostrovsky <boris.ostrov...@oracle.com>
---
 arch/x86/kernel/process.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 5e94c43..37fc577 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -667,6 +667,10 @@ static void amd_e400_idle(void)
  */
 static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c)
 {
+       /* Don't use MWAIT-C1 if explicitly requested */
+       if (boot_option_idle_override == IDLE_NOMWAIT)
+               return 0;
+
        if (c->x86_vendor != X86_VENDOR_INTEL)
                return 0;
 
-- 
1.8.3.1

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