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>

3 files changed, 26 insertions, 18 deletions

diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index 391e01387248..370298a0bca3 100644
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -147,8 +147,9 @@ END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,943)
 
 #define __EXCEPTION_PROLOG_1(area, extra, vec)                          \
         GET_PACA(r13);                                                  \
-        std     r9,area+EX_R9(r13);     /* save r9 - r12 */             \
-        std     r10,area+EX_R10(r13);                                   \
+        std     r9,area+EX_R9(r13);     /* save r9 */                   \
+        HMT_MEDIUM_PPR_SAVE(area, r9);                                  \
+        std     r10,area+EX_R10(r13);   /* save r10 - r12 */            \
         BEGIN_FTR_SECTION_NESTED(66);                                   \
         mfspr   r10,SPRN_CFAR;                                          \
         std     r10,area+EX_CFAR(r13);                                  \
@@ -264,6 +265,7 @@ do_kvm_##n:								\
         std     r10,GPR1(r1);           /* save r1 in stackframe        */ \
         beq     4f;                     /* if from kernel mode          */ \
         ACCOUNT_CPU_USER_ENTRY(r9, r10);                                   \
+        SAVE_PPR(area, r9, r10);                                           \
 4:      std     r2,GPR2(r1);            /* save r2 in stackframe        */ \
         SAVE_4GPRS(3, r1);              /* save r3 - r6 in stackframe   */ \
         SAVE_2GPRS(7, r1);              /* save r7, r8 in stackframe    */ \
@@ -305,7 +307,7 @@ do_kvm_##n:								\
         . = loc;                                        \
         .globl label##_pSeries;                         \
 label##_pSeries:                                        \
-        HMT_MEDIUM;                                     \
+        HMT_MEDIUM_PPR_DISCARD;                         \
         SET_SCRATCH0(r13);              /* save r13 */          \
         EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, label##_common,    \
                                  EXC_STD, KVMTEST_PR, vec)
@@ -314,7 +316,7 @@ label##_pSeries:					\
         . = loc;                                        \
         .globl label##_hv;                              \
 label##_hv:                                             \
-        HMT_MEDIUM;                                     \
+        HMT_MEDIUM_PPR_DISCARD;                         \
         SET_SCRATCH0(r13);      /* save r13 */                  \
         EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, label##_common,    \
                                  EXC_HV, KVMTEST, vec)
@@ -323,7 +325,7 @@ label##_hv:						\
         . = loc;                                        \
         .globl label##_relon_pSeries;                   \
 label##_relon_pSeries:                                  \
-        HMT_MEDIUM;                                     \
+        HMT_MEDIUM_PPR_DISCARD;                         \
         /* No guest interrupts come through here */     \
         SET_SCRATCH0(r13);              /* save r13 */  \
         EXCEPTION_RELON_PROLOG_PSERIES(PACA_EXGEN, label##_common, \
@@ -333,7 +335,7 @@ label##_relon_pSeries:					\
         . = loc;                                        \
         .globl label##_relon_hv;                        \
 label##_relon_hv:                                       \
-        HMT_MEDIUM;                                     \
+        HMT_MEDIUM_PPR_DISCARD;                         \
         /* No guest interrupts come through here */     \
         SET_SCRATCH0(r13);      /* save r13 */          \
         EXCEPTION_RELON_PROLOG_PSERIES(PACA_EXGEN, label##_common, \
@@ -371,7 +373,7 @@ label##_relon_hv:					\
 #define SOFTEN_NOTEST_HV(vec)           _SOFTEN_TEST(EXC_HV, vec)
 
 #define __MASKABLE_EXCEPTION_PSERIES(vec, label, h, extra)              \
-        HMT_MEDIUM;                                                     \
+        HMT_MEDIUM_PPR_DISCARD;                                         \
         SET_SCRATCH0(r13);    /* save r13 */                            \
         __EXCEPTION_PROLOG_1(PACA_EXGEN, extra, vec);           \
         EXCEPTION_PROLOG_PSERIES_1(label##_common, h);
@@ -393,7 +395,7 @@ label##_hv:								\
                                     EXC_HV, SOFTEN_TEST_HV)
 
 #define __MASKABLE_RELON_EXCEPTION_PSERIES(vec, label, h, extra)        \
-        HMT_MEDIUM;                                                     \
+        HMT_MEDIUM_PPR_DISCARD;                                         \
         SET_SCRATCH0(r13);    /* save r13 */                            \
         __EXCEPTION_PROLOG_1(PACA_EXGEN, extra, vec);           \
         EXCEPTION_RELON_PROLOG_PSERIES_1(label##_common, h);
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 7a70d0a6df3e..6faf51e165a5 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -227,6 +227,7 @@ END_FTR_SECTION_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
 
         beq-    1f
         ACCOUNT_CPU_USER_EXIT(r11, r12)
+        HMT_MEDIUM_LOW_HAS_PPR
         ld      r13,GPR13(r1)   /* only restore r13 if returning to usermode */
 1:      ld      r2,GPR2(r1)
         ld      r1,GPR1(r1)
@@ -303,6 +304,7 @@ syscall_exit_work:
         subi    r12,r12,TI_FLAGS
 
 4:      /* Anything else left to do? */
+        SET_DEFAULT_THREAD_PPR(r3, r9)          /* Set thread.ppr = 3 */
         andi.   r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP)
         beq     .ret_from_except_lite
 
@@ -758,6 +760,7 @@ fast_exception_return:
         andi.   r0,r3,MSR_PR
         beq     1f
         ACCOUNT_CPU_USER_EXIT(r2, r4)
+        RESTORE_PPR(r2, r4)
         REST_GPR(13, r1)
 1:
         mtspr   SPRN_SRR1,r3
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 32fc04f78890..3425aba8da51 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -104,7 +104,7 @@ __start_interrupts:
 
         .globl system_reset_pSeries;
 system_reset_pSeries:
-        HMT_MEDIUM;
+        HMT_MEDIUM_PPR_DISCARD
         SET_SCRATCH0(r13)
 #ifdef CONFIG_PPC_P7_NAP
 BEGIN_FTR_SECTION
@@ -158,7 +158,7 @@ machine_check_pSeries_1:
         . = 0x300
         .globl data_access_pSeries
 data_access_pSeries:
-        HMT_MEDIUM
+        HMT_MEDIUM_PPR_DISCARD
         SET_SCRATCH0(r13)
 BEGIN_FTR_SECTION
         b       data_access_check_stab
@@ -170,7 +170,7 @@ END_MMU_FTR_SECTION_IFCLR(MMU_FTR_SLB)
         . = 0x380
         .globl data_access_slb_pSeries
 data_access_slb_pSeries:
-        HMT_MEDIUM
+        HMT_MEDIUM_PPR_DISCARD
         SET_SCRATCH0(r13)
         EXCEPTION_PROLOG_1(PACA_EXSLB, KVMTEST, 0x380)
         std     r3,PACA_EXSLB+EX_R3(r13)
@@ -201,7 +201,7 @@ data_access_slb_pSeries:
         . = 0x480
         .globl instruction_access_slb_pSeries
 instruction_access_slb_pSeries:
-        HMT_MEDIUM
+        HMT_MEDIUM_PPR_DISCARD
         SET_SCRATCH0(r13)
         EXCEPTION_PROLOG_1(PACA_EXSLB, KVMTEST_PR, 0x480)
         std     r3,PACA_EXSLB+EX_R3(r13)
@@ -324,10 +324,11 @@ vsx_unavailable_pSeries_1:
         . = 0x1500
         .global denorm_exception_hv
 denorm_exception_hv:
-        HMT_MEDIUM
+        HMT_MEDIUM_PPR_DISCARD
         mtspr   SPRN_SPRG_HSCRATCH0,r13
         mfspr   r13,SPRN_SPRG_HPACA
         std     r9,PACA_EXGEN+EX_R9(r13)
+        HMT_MEDIUM_PPR_SAVE(PACA_EXGEN, r9)
         std     r10,PACA_EXGEN+EX_R10(r13)
         std     r11,PACA_EXGEN+EX_R11(r13)
         std     r12,PACA_EXGEN+EX_R12(r13)
@@ -369,7 +370,7 @@ denorm_exception_hv:
 machine_check_pSeries:
         .globl machine_check_fwnmi
 machine_check_fwnmi:
-        HMT_MEDIUM
+        HMT_MEDIUM_PPR_DISCARD
         SET_SCRATCH0(r13)               /* save r13 */
         EXCEPTION_PROLOG_PSERIES(PACA_EXMC, machine_check_common,
                                  EXC_STD, KVMTEST, 0x200)
@@ -498,6 +499,7 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_ARCH_206)
         mtspr   SPRN_HSRR0,r11
         mtcrf   0x80,r9
         ld      r9,PACA_EXGEN+EX_R9(r13)
+        RESTORE_PPR_PACA(PACA_EXGEN, r10)
         ld      r10,PACA_EXGEN+EX_R10(r13)
         ld      r11,PACA_EXGEN+EX_R11(r13)
         ld      r12,PACA_EXGEN+EX_R12(r13)
@@ -603,7 +605,7 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_HVMODE)
         .globl system_reset_fwnmi
       .align 7
 system_reset_fwnmi:
-        HMT_MEDIUM
+        HMT_MEDIUM_PPR_DISCARD
         SET_SCRATCH0(r13)               /* save r13 */
         EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, system_reset_common, EXC_STD,
                                  NOTEST, 0x100)
@@ -716,7 +718,7 @@ machine_check_common:
         . = 0x4380
         .globl data_access_slb_relon_pSeries
 data_access_slb_relon_pSeries:
-        HMT_MEDIUM
+        HMT_MEDIUM_PPR_DISCARD
         SET_SCRATCH0(r13)
         EXCEPTION_PROLOG_1(PACA_EXSLB, NOTEST, 0x380)
         std     r3,PACA_EXSLB+EX_R3(r13)
@@ -741,7 +743,7 @@ data_access_slb_relon_pSeries:
         . = 0x4480
         .globl instruction_access_slb_relon_pSeries
 instruction_access_slb_relon_pSeries:
-        HMT_MEDIUM
+        HMT_MEDIUM_PPR_DISCARD
         SET_SCRATCH0(r13)
         EXCEPTION_PROLOG_1(PACA_EXSLB, NOTEST, 0x480)
         std     r3,PACA_EXSLB+EX_R3(r13)
@@ -1062,6 +1064,7 @@ _GLOBAL(slb_miss_realmode)
         mtcrf   0x01,r9         /* slb_allocate uses cr0 and cr7 */
 .machine        pop
 
+        RESTORE_PPR_PACA(PACA_EXSLB, r9)
         ld      r9,PACA_EXSLB+EX_R9(r13)
         ld      r10,PACA_EXSLB+EX_R10(r13)
         ld      r11,PACA_EXSLB+EX_R11(r13)
@@ -1411,7 +1414,7 @@ initial_stab:
 
 #ifdef CONFIG_PPC_POWERNV
 _GLOBAL(opal_mc_secondary_handler)
-        HMT_MEDIUM
+        HMT_MEDIUM_PPR_DISCARD
         SET_SCRATCH0(r13)
         GET_PACA(r13)
         clrldi  r3,r3,2