linux-kernel - [10/30] x86, apic: use physical mode for IBM summit platforms

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Message-Id: <20100121041833.780502526@mini.kroah.org>
Date:	Wed, 20 Jan 2010 20:15:31 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Chris McDermott <lcm@...ux.vnet.ibm.com>,
	Yinghai Lu <yinghai@...nel.org>
Subject: [10/30] x86, apic: use physical mode for IBM summit platforms

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Suresh Siddha <suresh.b.siddha@...el.com>

commit dfea91d5a7c795fd6f4e1a97489a98e4e767463e upstream.

Chris McDermott from IBM confirmed that hurricane chipset in IBM summit
platforms doesn't support logical flat mode.  Irrespective of the other
things like apic_id's, total number of logical cpu's, Linux kernel
should default to physical mode for this system.

The 32-bit kernel does so using the OEM checks for the IBM summit
platform.  Add a similar OEM platform check for the 64bit kernel too.

Otherwise the linux kernel boot can hang on this platform under certain
bios/platform settings.

Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>
Tested-by: Ananth N Mavinakayanahalli <ananth@...ibm.com>
Cc: Chris McDermott <lcm@...ux.vnet.ibm.com>
Cc: Yinghai Lu <yinghai@...nel.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 arch/x86/kernel/apic/apic_flat_64.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/arch/x86/kernel/apic/apic_flat_64.c
+++ b/arch/x86/kernel/apic/apic_flat_64.c
@@ -240,6 +240,11 @@ static int physflat_acpi_madt_oem_check(
 		printk(KERN_DEBUG "system APIC only can use physical flat");
 		return 1;
 	}
+
+	if (!strncmp(oem_id, "IBM", 3) && !strncmp(oem_table_id, "EXA", 3)) {
+		printk(KERN_DEBUG "IBM Summit detected, will use apic physical");
+		return 1;
+	}
 #endif
 
 	return 0;


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