linux-kernel - [PATCH 3.12 21/88] powerpc: Fix definition of SIAR and SDAR registers

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Message-Id: <18fca9e193003164ef51aaccb13f3e7e31dcfda8.1468483951.git.jslaby@suse.cz>
Date:	Thu, 14 Jul 2016 10:15:13 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Thomas Huth <thuth@...hat.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 21/88] powerpc: Fix definition of SIAR and SDAR registers

From: Thomas Huth <thuth@...hat.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit d23fac2b27d94aeb7b65536a50d32bfdc21fe01e upstream.

The SIAR and SDAR registers are available twice, one time as SPRs
780 / 781 (unprivileged, but read-only), and one time as the SPRs
796 / 797 (privileged, but read and write). The Linux kernel code
currently uses the unprivileged  SPRs - while this is OK for reading,
writing to that register of course does not work.
Since the KVM code tries to write to this register, too (see the mtspr
in book3s_hv_rmhandlers.S), the contents of this register sometimes get
lost for the guests, e.g. during migration of a VM.
To fix this issue, simply switch to the privileged SPR numbers instead.

Signed-off-by: Thomas Huth <thuth@...hat.com>
Acked-by: Paul Mackerras <paulus@...abs.org>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 arch/powerpc/include/asm/reg.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 3ce6b7b5ca19..ad261d56ae39 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -681,13 +681,13 @@
 #define SPRN_PMC6	792
 #define SPRN_PMC7	793
 #define SPRN_PMC8	794
-#define SPRN_SIAR	780
-#define SPRN_SDAR	781
 #define SPRN_SIER	784
 #define   SIER_SIPR		0x2000000	/* Sampled MSR_PR */
 #define   SIER_SIHV		0x1000000	/* Sampled MSR_HV */
 #define   SIER_SIAR_VALID	0x0400000	/* SIAR contents valid */
 #define   SIER_SDAR_VALID	0x0200000	/* SDAR contents valid */
+#define SPRN_SIAR	796
+#define SPRN_SDAR	797
 
 /* When EBB is enabled, some of MMCR0/MMCR2/SIER are user accessible */
 #define MMCR0_USER_MASK	(MMCR0_FC | MMCR0_PMXE | MMCR0_PMAO)
-- 
2.9.1