linux-kernel - [PATCH 1/2] x86: fix keeping track of AMD C1E

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Message-ID: <20100713185957.2866.50995.stgit@localhost.localdomain>
Date:	Tue, 13 Jul 2010 20:59:58 +0200
From:	Michal Schmidt <mschmidt@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Shaohua Li <shaohua.li@...el.com>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH 1/2] x86: fix keeping track of AMD C1E

On my system with AMD Phenom II X6 I am seeing pauses at boot (usually during
udev startup) which require a key press to continue. It only happens if C1E is
enabled in the BIOS.

It's caused by the APIC timer's inability to wake up the CPU from C1E (AMD
erratum #400). Linux has a workaround for it, but it's not being applied
correctly in this case. Though c1e_idle() detects C1E just fine, by the time
acpi_idle ('processor.ko' module) takes over, it is forgotten.

After AMD C1E is detected, it is not sufficient to flag it in boot_cpu_data,
because the flag will get cleared in identify_cpu() when more CPUs are brought
up later. The fix is to mark the flag as forced.

The additional call to set_cpu_cap() is just to make sure the flag is set even
on the CPUs that are already up and /proc/cpuinfo shows 'amdc1e' on all.

Also fix indentation in the function.

Signed-off-by: Michal Schmidt <mschmidt@...hat.com>
---

 arch/x86/kernel/process.c |    9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index e7e3521..f3520a8 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -589,7 +589,7 @@ static void c1e_idle(void)
 			if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
 				mark_tsc_unstable("TSC halt in AMD C1E");
 			printk(KERN_INFO "System has AMD C1E enabled\n");
-			set_cpu_cap(&boot_cpu_data, X86_FEATURE_AMDC1E);
+			setup_force_cpu_cap(X86_FEATURE_AMDC1E);
 		}
 	}

@@ -605,6 +605,7 @@ static void c1e_idle(void)
 					   &cpu);
 			printk(KERN_INFO "Switch to broadcast mode on CPU%d\n",
 			       cpu);
+			set_cpu_cap(&current_cpu_data, X86_FEATURE_AMDC1E);
 		}
 		clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);

@@ -614,9 +615,9 @@ static void c1e_idle(void)
 		 * The switch back from broadcast mode needs to be
 		 * called with interrupts disabled.
 		 */
-		 local_irq_disable();
-		 clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
-		 local_irq_enable();
+		local_irq_disable();
+		clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
+		local_irq_enable();
 	} else
 		default_idle();
 }

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