[tip:x86/platform] x86/platform/uv: Insert per_cpu accessor function on uv_hub_nmi

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Commit-ID:  7c52198b9c36001d47e11d50f7f1556805c5c3e3
Gitweb:     http://git.kernel.org/tip/7c52198b9c36001d47e11d50f7f1556805c5c3e3
Author:     George Beshers <gbeshers@xxxxxxx>
AuthorDate: Sat, 12 Sep 2015 21:51:05 -0500
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Sun, 13 Sep 2015 09:27:53 +0200

x86/platform/uv: Insert per_cpu accessor function on uv_hub_nmi

UV: NMI: insert this_cpu_read accessor function on uv_hub_nmi.

On SGI UV systems a 'power nmi' command from the CMC causes
all processors to drop into uv_handle_nmi().  With the 4.0
kernel this results in

    BUG: unable to handle kernel paging request

The bug is caused by the current code trying to use the PER_CPU
variable uv_cpu_nmi.hub without an appropriate accessor
function. That oversight occurred in

    commit e16321709c82 ("uv: Replace __get_cpu_var")
    Author: Christoph Lameter <cl@xxxxxxxxx>
    Date:   Sun Aug 17 12:30:41 2014 -0500

This patch inserts this_cpu_read() in the uv_hub_nmi macro
restoring the intended functionality.

Signed-off-by: George Beshers <gbeshers@xxxxxxx>
Acked-by: Mike Travis <travis@xxxxxxx>
Cc: Alex Thorlton <athorlton@xxxxxxx>
Cc: Dimitri Sivanich <sivanich@xxxxxxx>
Cc: Hedi Berriche <hedi@xxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Russ Anderson <rja@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/include/asm/uv/uv_hub.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/uv/uv_hub.h b/arch/x86/include/asm/uv/uv_hub.h
index a00ad8f..ea707478 100644
--- a/arch/x86/include/asm/uv/uv_hub.h
+++ b/arch/x86/include/asm/uv/uv_hub.h
@@ -609,7 +609,7 @@ struct uv_cpu_nmi_s {
 
 DECLARE_PER_CPU(struct uv_cpu_nmi_s, uv_cpu_nmi);
 
-#define uv_hub_nmi			(uv_cpu_nmi.hub)
+#define uv_hub_nmi			this_cpu_read(uv_cpu_nmi.hub)
 #define uv_cpu_nmi_per(cpu)		(per_cpu(uv_cpu_nmi, cpu))
 #define uv_hub_nmi_per(cpu)		(uv_cpu_nmi_per(cpu).hub)
 
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