linux-kernel - [PATCH] x86, UV: initialize BAU MMRs only on hubs with cpus

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Message-Id: <E1OZmZN-0006cW-RC@eag09.americas.sgi.com>
Date:	Fri, 16 Jul 2010 10:11:21 -0500
From:	Cliff Wickman <cpw@....com>
To:	mingo@...e.hu
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] x86, UV: initialize BAU MMRs only on hubs with cpus


Remove the initialization of MMRs UVH_LB_BAU_SB_ACTIVATION_CONTROL and
UVH_BAU_DATA_BROADCAST on UV hubs that have no active cpus.
Such initialization on hubs with no active cpus would result in a kernel
page fault.

This is not of real high priority, because we don't have any such systems
(with UV hubs that have no active cpus).  But they will be coming.

Diffed against 2.6.35-rc4
Signed-off-by: Cliff Wickman <cpw@....com>
---
 arch/x86/kernel/tlb_uv.c |   16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

Index: linux/arch/x86/kernel/tlb_uv.c
===================================================================
--- linux.orig/arch/x86/kernel/tlb_uv.c
+++ linux/arch/x86/kernel/tlb_uv.c
@@ -1634,12 +1634,16 @@ static int __init uv_bau_init(void)
 	alloc_intr_gate(vector, uv_bau_message_intr1);
 
 	for_each_possible_blade(uvhub) {
-		pnode = uv_blade_to_pnode(uvhub);
-		/* INIT the bau */
-		uv_write_global_mmr64(pnode, UVH_LB_BAU_SB_ACTIVATION_CONTROL,
-				      ((unsigned long)1 << 63));
-		mmr = 1; /* should be 1 to broadcast to both sockets */
-		uv_write_global_mmr64(pnode, UVH_BAU_DATA_BROADCAST, mmr);
+		if (uv_blade_nr_possible_cpus(uvhub)) {
+			pnode = uv_blade_to_pnode(uvhub);
+			/* INIT the bau */
+			uv_write_global_mmr64(pnode,
+					UVH_LB_BAU_SB_ACTIVATION_CONTROL,
+					((unsigned long)1 << 63));
+			mmr = 1; /* should be 1 to broadcast to both sockets */
+			uv_write_global_mmr64(pnode, UVH_BAU_DATA_BROADCAST,
+						mmr);
+		}
 	}
 
 	return 0;
--
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