powerpc: Per process DSCR + some fixes (try#4)

The DSCR (aka Data Stream Control Register) is supported on some
server PowerPC chips and allow some control over the prefetch
of data streams.

This patch allows the value to be specified per thread by emulating
the corresponding mfspr and mtspr instructions. Children of such
threads inherit the value. Other threads use a default value that
can be specified in sysfs - /sys/devices/system/cpu/dscr_default.

If a thread starts with non default value in the sysfs entry,
all children threads inherit this non default value even if
the sysfs value is changed later.

Signed-off-by: Alexey Kardashevskiy <aik@au1.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/ppc-opcode.h b/arch/powerpc/include/asm/ppc-opcode.h
index 3e25b258568e..e472659d906c 100644
--- a/arch/powerpc/include/asm/ppc-opcode.h
+++ b/arch/powerpc/include/asm/ppc-opcode.h
@@ -41,6 +41,10 @@
 #define PPC_INST_RFCI                   0x4c000066
 #define PPC_INST_RFDI                   0x4c00004e
 #define PPC_INST_RFMCI                  0x4c00004c
+#define PPC_INST_MFSPR_DSCR             0x7c1102a6
+#define PPC_INST_MFSPR_DSCR_MASK        0xfc1fffff
+#define PPC_INST_MTSPR_DSCR             0x7c1103a6
+#define PPC_INST_MTSPR_DSCR_MASK        0xfc1fffff
 
 #define PPC_INST_STRING                 0x7c00042a
 #define PPC_INST_STRING_MASK            0xfc0007fe