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From: Zhenzhong Duan <zhenzhong.duan@oracle.com>
To: linux-kernel@vger.kernel.org
Cc: x86@kernel.org, tim.c.chen@linux.intel.com,
	Zhenzhong Duan <zhenzhong.duan@oracle.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@redhat.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: [PATCH] x86: Don't use MWAIT if explicitly requested
Date: Fri, 18 Oct 2019 11:45:54 +0800	[thread overview]
Message-ID: <1571370354-17736-1-git-send-email-zhenzhong.duan@oracle.com> (raw)

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.duan@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Boris Ostrovsky <boris.ostrovsky@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


             reply	other threads:[~2019-10-18  5:55 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-18  3:45 Zhenzhong Duan [this message]
2019-10-18  7:12 ` [PATCH] x86: Don't use MWAIT if explicitly requested Peter Zijlstra
2019-10-18  8:47   ` Zhenzhong Duan

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