[tip:x86/urgent] x86/platform/UV: Fix kernel panic running RHEL kdump kernel on UV systems

[tip-bot for Mike Travis]

Commit-ID:  5a52e8f822374bebc702bb2688ed8b5515bbb55b
Gitweb:     http://git.kernel.org/tip/5a52e8f822374bebc702bb2688ed8b5515bbb55b
Author:     Mike Travis <travis@xxxxxxx>
AuthorDate: Mon, 1 Aug 2016 13:40:53 -0500
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 10 Aug 2016 15:55:39 +0200

x86/platform/UV: Fix kernel panic running RHEL kdump kernel on UV systems

The latest UV kernel support panics when RHEL7 kexec's the kdump kernel
to make a dumpfile.  This patch fixes the problem by turning off all UV
support if NUMA is off.

Tested-by: Frank Ramsay <framsay@xxxxxxx>
Tested-by: John Estabrook <estabrook@xxxxxxx>
Signed-off-by: Mike Travis <travis@xxxxxxx>
Reviewed-by: Dimitri Sivanich <sivanich@xxxxxxx>
Reviewed-by: Nathan Zimmer <nzimmer@xxxxxxx>
Cc: Alex Thorlton <athorlton@xxxxxxx>
Cc: Andrew Banman <abanman@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Russ Anderson <rja@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20160801184050.577755634@xxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/kernel/apic/x2apic_uv_x.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/kernel/apic/x2apic_uv_x.c b/arch/x86/kernel/apic/x2apic_uv_x.c
index 6aa0545..cb0673c 100644
--- a/arch/x86/kernel/apic/x2apic_uv_x.c
+++ b/arch/x86/kernel/apic/x2apic_uv_x.c
@@ -223,6 +223,11 @@ static int __init uv_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
 	if (strncmp(oem_id, "SGI", 3) != 0)
 		return 0;
 
+	if (numa_off) {
+		pr_err("UV: NUMA is off, disabling UV support\n");
+		return 0;
+	}
+
 	/* Setup early hub type field in uv_hub_info for Node 0 */
 	uv_cpu_info->p_uv_hub_info = &uv_hub_info_node0;