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

From: Jiri Slaby
Date: Thu Jul 14 2016 - 04:43:46 EST

From: Thomas Huth <thuth@xxxxxxxxxx>

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@xxxxxxxxxx>
Acked-by: Paul Mackerras <paulus@xxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
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 */