linux-kernel - [tip:x86/apic] x86/apic: Avoid open coded x2apic detection

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Date:	Thu, 22 Jan 2015 06:24:40 -0800
From:	tip-bot for Thomas Gleixner <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	tglx@...utronix.de, jiang.liu@...ux.intel.com,
	linux-kernel@...r.kernel.org, mingo@...nel.org, bp@...en8.de,
	joro@...tes.org, hpa@...or.com, tony.luck@...el.com
Subject: [tip:x86/apic] x86/apic: Avoid open coded x2apic detection

Commit-ID:  8d80696060eedf49c080c0f2cf39a20ae7e787f9
Gitweb:     http://git.kernel.org/tip/8d80696060eedf49c080c0f2cf39a20ae7e787f9
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Thu, 15 Jan 2015 21:22:09 +0000
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Thu, 22 Jan 2015 15:10:54 +0100

x86/apic: Avoid open coded x2apic detection

enable_IR_x2apic() grew a open coded x2apic detection. Implement a
proper helper function which shares the code with the already existing
x2apic_enabled().

Made it use rdmsrl_safe as suggested by Boris.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Jiang Liu <jiang.liu@...ux.intel.com>
Cc: Joerg Roedel <joro@...tes.org>
Cc: Tony Luck <tony.luck@...el.com>
Link: http://lkml.kernel.org/r/20150115211702.285038186@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/include/asm/apic.h | 19 ++++++++++---------
 arch/x86/kernel/apic/apic.c |  5 +----
 2 files changed, 11 insertions(+), 13 deletions(-)

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 465b309..1a8ba26 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -108,6 +108,15 @@ extern u64 native_apic_icr_read(void);
 
 extern int x2apic_mode;
 
+static inline bool apic_is_x2apic_enabled(void)
+{
+	u64 msr;
+
+	if (rdmsrl_safe(MSR_IA32_APICBASE, &msr))
+		return false;
+	return msr & X2APIC_ENABLE;
+}
+
 #ifdef CONFIG_X86_X2APIC
 /*
  * Make previous memory operations globally visible before
@@ -175,15 +184,7 @@ extern void check_x2apic(void);
 extern void enable_x2apic(void);
 static inline int x2apic_enabled(void)
 {
-	u64 msr;
-
-	if (!cpu_has_x2apic)
-		return 0;
-
-	rdmsrl(MSR_IA32_APICBASE, msr);
-	if (msr & X2APIC_ENABLE)
-		return 1;
-	return 0;
+	return cpu_has_x2apic && apic_is_x2apic_enabled();
 }
 
 #define x2apic_supported()	(cpu_has_x2apic)
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 35e6d09..7ecfce1 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1625,10 +1625,7 @@ void __init enable_IR_x2apic(void)
 	int ret, ir_stat;
 
 	if (!IS_ENABLED(CONFIG_X86_X2APIC)) {
-		u64 msr;
-
-		rdmsrl(MSR_IA32_APICBASE, msr);
-		if (msr & X2APIC_ENABLE)
+		if (apic_is_x2apic_enabled())
 			panic("BIOS has enabled x2apic but kernel doesn't support x2apic, please disable x2apic in BIOS.\n");
 	}
 
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