From: Brad Peters <bpeters@redhat.com>
Date: Tue, 1 Apr 2008 14:58:57 -0400
Subject: [ppc64] SLB shadow buffer error cause random reboots
Message-id: 47F285F1.7070100@redhat.com
O-Subject: [RHEL 5.2] SLB shadow buffer error causes random rebooting - Last minute snap4 patch, PLEASE REVIEW
Bugzilla: 440085

Description:
------------
This was a bug introduced with a new feature: "RHBZ 253112 SLB shadow buffer support".  The bug causes frequent, random system reboots on any system with SLB buffering enabled in the firmware.

The patch addresses this problem by invalidating a portion of a new shadow buffer prior to registering it as a new one.  Prior to this, we saw old buffer's with stale entries being used as valid, leading to the witnessed rebooting.

RHBZ#:
------
440085

RHEL Version Found:
------------------
RHEL 5.2

kABI Status:
------------
No symbols were harmed.

Brew:
-----
http://brewweb.devel.redhat.com/brew/taskinfo?taskID=1237642

Kernel binary rpm available at:
-----
Will provide a followup email with a link shortly.

Upstream Status:
----------------
Upstream in the following patches:

473980a99316c0e788bca50996375a2815124ce1
[POWERPC] Fix CPU hotplug when using the SLB shadow buffer

dfbe0d3b6be52596b5694b1bb75b19562e769021
[POWERPC] Fix boot failure on POWER6

Test Status:
-------------
Tested as shown to stop rebooting:
Nathan Lynch, 3/28 <nathanl@austin.ibm.com>

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

Brad Peters 1-978-392-1000 x 23183
IBM on-site partner.

Proposed Patch:
---------------
This patch is based on 2.6.18-87.el5

Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>

diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c
index c1469d6..4deeafe 100644
--- a/arch/powerpc/mm/slb.c
+++ b/arch/powerpc/mm/slb.c
@@ -255,6 +255,8 @@ void slb_initialize(void)
 
 	create_shadowed_slbe(VMALLOC_START, vflags, 1);
 
+	slb_shadow_clear(2);
+
 	/* We don't bolt the stack for the time being - we're in boot,
 	 * so the stack is in the bolted segment.  By the time it goes
 	 * elsewhere, we'll call _switch() which will bolt in the new
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 6948f5f..32d59c3 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -347,6 +347,7 @@ static void pSeries_mach_cpu_die(void)
 	local_irq_disable();
 	idle_task_exit();
 	xics_teardown_cpu();
+	unregister_slb_shadow(hard_smp_processor_id(), __pa(get_slb_shadow()));
 	rtas_stop_self();
 	/* Should never get here... */
 	BUG();