powerpc: Hide some system call labels from profile tools

syscall_dotrace_cont and syscall_error_cont tend to complicate perf
output so make them local.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
(cherry picked from commit d14299dec74a094b0f26b0893eccf8aefdfbd007)
powerpc: No need to save XER in a system call

The XER is a volatile register so there is no need to save and restore
it over a system call - zero it out in the exception stack frame
instead.

This should fix a 5 cycle stall of the mfxer/std seen on POWER7.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
(cherry picked from commit 823df43552da39fd48a2dd74949363a1c8cf62bb)
powerpc: No need to preserve count register across system call

The count register is volatile so we don't need to preserve it.
Store zero to the entry in the exception frame.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
(cherry picked from commit 82087414c608440c5ca7faa5c2fb6327daebcd15)
powerpc: Better scheduling of CR save code in system call path

At the moment system call entry looks like:

crclr	so
...
mfcr	r9
...
std	r9,_CCR(r1)

commit bd19c8994a82 ([POWERPC] system call micro optimisation) put
some space between the crclr and mfcr in order to avoid a stall.

There is still a stall seen between the mfcr and std. We can avoid
the crclr by doing it in a GPR with rlwinm which gives us more room
to better schedule the sequence.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
(cherry picked from commit fd6c40f3b00a1e76d6a920cb6591907c53450afc)
powerpc: Move branch instruction from ACCOUNT_CPU_USER_ENTRY to caller

[PATCH 1/6] powerpc: Move branch instruction from ACCOUNT_CPU_USER_ENTRY to caller

The first instruction in ACCOUNT_CPU_USER_ENTRY is 'beq' which checks for
exceptions coming from kernel mode. PPR value will be saved immediately after
ACCOUNT_CPU_USER_ENTRY and is also for user level exceptions. So moved this
branch instruction in the caller code.

Signed-off-by: Haren Myneni <haren@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
(cherry picked from commit 5d75b26443aff37a7bd356f9dbd6d6e11ec122aa)
powerpc: Enable PPR save/restore

[PATCH 2/6] powerpc: Enable PPR save/restore

SMT thread status register (PPR) is used to set thread priority. This patch
enables PPR save/restore feature (CPU_FTR_HAS_PPR) on POWER7 and POWER8 systems.

Signed-off-by: Haren Myneni <haren@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
(cherry picked from commit d261386852178ce0bdf836f7c92267f21c8bb3f9)
powerpc: Increase exceptions arrays in paca struct to save PPR

[PATCH 3/6] powerpc: Increase exceptions arrays in paca struct to save PPR

Using paca to save user defined PPR value in the first level exception vector.

Signed-off-by: Haren Myneni <haren@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
(cherry picked from commit a09688cd23d477ebd9c8f57881bfe907240cb0a1)
powerpc: Define ppr in thread_struct

[PATCH 4/6] powerpc: Define ppr in thread_struct

ppr in thread_struct is used to save PPR and restore it before process exits
from kernel.

This patch sets the default priority to 3 when tasks are created such
that users can use 4 for higher priority tasks.

Signed-off-by: Haren Myneni <haren@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
(cherry picked from commit 92779245599bb3d7fb48066b11c4bfd6aa477198)
powerpc: Macros for saving/restore PPR

[PATCH 5/6] powerpc: Macros for saving/restore PPR

Several macros are defined for saving and restore user defined PPR value.

Signed-off-by: Haren Myneni <haren@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
(cherry picked from commit 13e7a8e846c2ea38a552b986ea49332f965bbb7a)
powerpc: Implement PPR save/restore

[PATCH 6/6] powerpc: Implement PPR save/restore

When the task enters in to kernel space, the user defined priority (PPR)
will be saved in to PACA at the beginning of first level exception
vector and then copy from PACA to thread_info in second level vector.
PPR will be restored from thread_info before exits the kernel space.

P7/P8 temporarily raises the thread priority to higher level during
exception until the program executes HMT_* calls. But it will not modify
PPR register. So we save PPR value whenever some register is available
to use and then calls HMT_MEDIUM to increase the priority. This feature
supports on P7 or later processors.

We save/ restore PPR for all exception vectors except system call entry.
GLIBC will be saving / restore for system calls. So the default PPR
value (3) will be set for the system call exit when the task returned
to the user space.

Signed-off-by: Haren Myneni <haren@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
(cherry picked from commit 44e9309f1f357794b7ae93d5f3e3e6f11d2b8a7f)