From: Scott Moser <smoser@redhat.com>
Subject: [PATCH RHEL5.1] bz249910 [ppc] DATA CORRUPTION:Axon memory does not handle double bit errors
Date: Mon, 30 Jul 2007 10:38:15 -0400 (EDT)
Bugzilla: 249910
Message-Id: <Pine.LNX.4.64.0707301037040.30310@squad5-lp1.lab.boston.redhat.com>
Changelog: [ppc] Axon memory does not handle double bit errors


RHBZ#: 249910
------
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=249910

Description:
------------
The problem is that Axon memory does not handle double bit errors (at
least detect them like it is for other eServers) and that this might lead
to corrupted data. IBM's memory policy is that single bit errors must be
detected and corrected and that double bit errors must be detected. Axon
is failing this policy. The system design today allows only Linux to react
on this (via reacting on an interrupt) too late, so the corrupted data
might be already transferred. Hence the system design must be changed that
Linux is not reacting on those interrupts, instead the firmware must route
those interrupts to a fast reacting HW instance. The attached patch will
turn off the Linux reaction for certain interrupts.

RHEL Version Found:
-------------------
This is a bug found in RHEL5u1 kernel 2.6.18-36.el5.

Upstream Status:
----------------
This upstream git-commit is, in 2.6.23-rc1:
   7fd7218610600b16f6f0af3f9d9353ba0265c09f

Test Status:
------------
To ensure cross-platform build, this code has been built with brew
--scratch against a 2.6.18-36.el5 kernel and is available at [1].

This code has been tested by Ben Herrenschmidt of IBM on top of
2.6.18-36.el5.

Proposed Patch:
----------------
Please review and ACK for RHEL5.1

--
---
 arch/powerpc/sysdev/mpic.c |   36 +++++++++++++++++++++++++++++++++++-
 include/asm-powerpc/mpic.h |    3 +++
 2 files changed, 38 insertions(+), 1 deletion(-)

Index: b/arch/powerpc/sysdev/mpic.c
===================================================================
--- a/arch/powerpc/sysdev/mpic.c
+++ b/arch/powerpc/sysdev/mpic.c
@@ -824,6 +824,8 @@ static int mpic_host_map(struct irq_host
 
 	if (hw >= mpic->irq_count)
 		return -EINVAL;
+	if (mpic->protected && test_bit(hw, mpic->protected))
+		return -EINVAL;
 
 	/* Default chip */
 	chip = &mpic->hc_irq;
@@ -948,7 +950,6 @@ struct mpic * __init mpic_alloc(struct d
 	if (node && get_property(node, "big-endian", NULL) != NULL)
 		mpic->flags |= MPIC_BIG_ENDIAN;
 
-
 #ifdef CONFIG_MPIC_WEIRD
 	mpic->hw_set = mpic_infos[MPIC_GET_REGSET(flags)];
 #endif
@@ -1125,11 +1126,35 @@ void __init mpic_init(struct mpic *mpic)
 	if ((mpic->flags & MPIC_BROKEN_U3) && (mpic->flags & MPIC_PRIMARY))
  		mpic_scan_ht_pics(mpic);
 
+	/* Look for protected sources */
+	if (mpic->of_node) {
+		unsigned int psize, mapsize;
+		const u32 *psrc =
+			get_property(mpic->of_node, "protected-sources",
+				     &psize);
+		if (psrc) {
+			psize /= 4;
+			mapsize = BITS_TO_LONGS(mpic->num_sources) *
+				sizeof(unsigned long);
+			mpic->protected = alloc_bootmem(mapsize);
+			BUG_ON(mpic->protected == NULL);
+			memset(mpic->protected, 0, mapsize);
+			for (i = 0; i < psize; i++) {
+				if (psrc[i] > mpic->num_sources)
+					continue;
+				__set_bit(psrc[i], mpic->protected);
+			}
+		}
+	}
+
 	for (i = 0; i < mpic->num_sources; i++) {
 		/* start with vector = source number, and masked */
 		u32 vecpri = MPIC_VECPRI_MASK | i |
 			(8 << MPIC_VECPRI_PRIORITY_SHIFT);
 		
+		/* check if protected */
+		if (mpic->protected && test_bit(i, mpic->protected))
+			continue;
 		/* init hw */
 		mpic_irq_write(i, MPIC_INFO(IRQ_VECTOR_PRI), vecpri);
 		mpic_irq_write(i, MPIC_INFO(IRQ_DESTINATION),
@@ -1315,6 +1340,15 @@ unsigned int mpic_get_one_irq(struct mpi
 #endif
 	if (unlikely(src == MPIC_VEC_SPURRIOUS))
 		return NO_IRQ;
+
+	if (unlikely(mpic->protected && test_bit(src, mpic->protected))) {
+		if (printk_ratelimit())
+			printk(KERN_WARNING "%s: Got protected source %d !\n",
+			       mpic->name, (int)src);
+		mpic_eoi(mpic);
+		return NO_IRQ;
+	}
+
 	return irq_linear_revmap(mpic->irqhost, src);
 }
 
Index: b/include/asm-powerpc/mpic.h
===================================================================
--- a/include/asm-powerpc/mpic.h
+++ b/include/asm-powerpc/mpic.h
@@ -295,6 +295,9 @@ struct mpic
 	unsigned int		dcr_base;
 #endif
 
+	/* Protected sources */
+	unsigned long		*protected;
+
 #ifdef CONFIG_MPIC_WEIRD
 	/* Pointer to HW info array */
 	u32			*hw_set;