[PATCH][RFC] x86: override prefer_mwait_c1_over_halt to avoid loading cpuidle-haltpoll driver

[lirongqing@baidu.com]

From: Li RongQing <lirongqing@baidu.com>

x86 KVM guests with MWAIT can load cpuidle-haltpoll driver, and will
cause performance degradation, so override prefer_mwait_c1_over_halt
to a new value, aviod loading cpuidle-haltpoll driver

Signed-off-by: Li RongQing <lirongqing@baidu.com>
---
 arch/x86/include/asm/processor.h | 2 +-
 arch/x86/kernel/process.c        | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 67c9d73..6bc94fd 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -658,7 +658,7 @@ extern void amd_e400_c1e_apic_setup(void);
 extern unsigned long		boot_option_idle_override;
 
 enum idle_boot_override {IDLE_NO_OVERRIDE=0, IDLE_HALT, IDLE_NOMWAIT,
-			 IDLE_POLL};
+			 IDLE_POLL, IDLE_PREF_MWAIT};
 
 extern void enable_sep_cpu(void);
 extern int sysenter_setup(void);
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index c21b734..a16985c 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -889,6 +889,7 @@ void select_idle_routine(const struct cpuinfo_x86 *c)
 	} else if (prefer_mwait_c1_over_halt(c)) {
 		pr_info("using mwait in idle threads\n");
 		x86_idle = mwait_idle;
+		boot_option_idle_override = IDLE_PREF_MWAIT;
 	} else if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST)) {
 		pr_info("using TDX aware idle routine\n");
 		x86_idle = tdx_safe_halt;
-- 
2.9.4