linux-kernel - [GIT pull] x86 fix for 4.2

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Message-ID: <alpine.DEB.2.11.1508251010350.15006@nanos>
Date:	Tue, 25 Aug 2015 10:13:55 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [GIT pull] x86 fix for 4.2

Linus,

please pull the latest x86-urgent-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-urgent-for-linus

A single fix for a APIC regression introduced in 4.0 which went
undetected until now. I screwed up the x2apic cleanup in a subtle
way. The screwup is only visible on systems which have x2apic
preenabled in the BIOS and need to disable it during boot.

Thanks,

	tglx

------------------>
Thomas Gleixner (1):
      x86/apic: Fix fallout from x2apic cleanup


 arch/x86/kernel/apic/apic.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index dcb52850a28f..cde732c1b495 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1424,7 +1424,7 @@ static inline void __x2apic_disable(void)
 {
 	u64 msr;
 
-	if (cpu_has_apic)
+	if (!cpu_has_apic)
 		return;
 
 	rdmsrl(MSR_IA32_APICBASE, msr);
@@ -1483,10 +1483,13 @@ void x2apic_setup(void)
 
 static __init void x2apic_disable(void)
 {
-	u32 x2apic_id;
+	u32 x2apic_id, state = x2apic_state;
 
-	if (x2apic_state != X2APIC_ON)
-		goto out;
+	x2apic_mode = 0;
+	x2apic_state = X2APIC_DISABLED;
+
+	if (state != X2APIC_ON)
+		return;
 
 	x2apic_id = read_apic_id();
 	if (x2apic_id >= 255)
@@ -1494,9 +1497,6 @@ static __init void x2apic_disable(void)
 
 	__x2apic_disable();
 	register_lapic_address(mp_lapic_addr);
-out:
-	x2apic_state = X2APIC_DISABLED;
-	x2apic_mode = 0;
 }
 
 static __init void x2apic_enable(void)
--
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