[RFC PATCH 02/14] powerpc/tm: Reclaim on unavailable exception

[Breno Leitao]

If there is a FP/VEC/Altivec touch inside a transaction and the facility is
disabled, then a facility unavailable exception is raised and ends up
calling {fp,vec,vsx}_unavailable_tm, which was reclaiming and
recheckpointing.

This is not required anymore, since the checkpointed state was reclaimed in
the exception entrance, and it will be recheckpointed by restore_tm_state
later.

Adding a WARN_ON() warning if we hit the _unavailable_tm() in suspended
mode, i.e, the reclaim was not executed somehow in the trap entrance, and
this is a bug.

Signed-off-by: Breno Leitao <lei...@debian.org>
---
 arch/powerpc/include/asm/exception-64s.h |  4 ++++
 arch/powerpc/kernel/exceptions-64s.S     |  3 +++
 arch/powerpc/kernel/traps.c              | 22 ++++------------------
 3 files changed, 11 insertions(+), 18 deletions(-)

diff --git a/arch/powerpc/include/asm/exception-64s.h 
b/arch/powerpc/include/asm/exception-64s.h
index 931a74ba037b..80f01d5683c3 100644
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -711,6 +711,10 @@ END_FTR_SECTION_IFSET(CPU_FTR_CTRL)
         * Soft disable the IRQs, otherwise it might cause a CPU hang.  \
         */                                                             \
        RECONCILE_IRQ_STATE(r10, r11);                                  \
+       /*                                                              \
+        * Although this cause will be set initially, it might be       \
+        * updated later, once the exception is better understood       \
+        */                                                             \
        li      r3, cause;                                              \
        bl      tm_reclaim_current;                                     \
        li      r3, 1;          /* Reclaim happened */                  \
diff --git a/arch/powerpc/kernel/exceptions-64s.S 
b/arch/powerpc/kernel/exceptions-64s.S
index 5c685a46202d..47e05b09eed6 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -786,6 +786,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_TM)
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 2:     /* User process was in a transaction */
        bl      save_nvgprs
+       TM_KERNEL_ENTRY(TM_CAUSE_FAC_UNAV)
        RECONCILE_IRQ_STATE(r10, r11)
        addi    r3,r1,STACK_FRAME_OVERHEAD
        bl      fp_unavailable_tm
@@ -1128,6 +1129,7 @@ BEGIN_FTR_SECTION
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 2:     /* User process was in a transaction */
        bl      save_nvgprs
+       TM_KERNEL_ENTRY(TM_CAUSE_FAC_UNAV)
        RECONCILE_IRQ_STATE(r10, r11)
        addi    r3,r1,STACK_FRAME_OVERHEAD
        bl      altivec_unavailable_tm
@@ -1164,6 +1166,7 @@ BEGIN_FTR_SECTION
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 2:     /* User process was in a transaction */
        bl      save_nvgprs
+       TM_KERNEL_ENTRY(TM_CAUSE_FAC_UNAV)
        RECONCILE_IRQ_STATE(r10, r11)
        addi    r3,r1,STACK_FRAME_OVERHEAD
        bl      vsx_unavailable_tm
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 9a86572db1ef..e74b735e974c 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -1742,23 +1742,10 @@ void fp_unavailable_tm(struct pt_regs *regs)
          * transaction, and probably retry but now with FP enabled.  So the
          * checkpointed FP registers need to be loaded.
         */
-       tm_reclaim_current(TM_CAUSE_FAC_UNAV);
-
-       /*
-        * Reclaim initially saved out bogus (lazy) FPRs to ckfp_state, and
-        * then it was overwrite by the thr->fp_state by tm_reclaim_thread().
-        *
-        * At this point, ck{fp,vr}_state contains the exact values we want to
-        * recheckpoint.
-        */
+       WARN_ON(MSR_TM_SUSPENDED(mfmsr()));
 
        /* Enable FP for the task: */
        current->thread.load_fp = 1;
-
-       /*
-        * Recheckpoint all the checkpointed ckpt, ck{fp, vr}_state registers.
-        */
-       tm_recheckpoint(&current->thread);
 }
 
 void altivec_unavailable_tm(struct pt_regs *regs)
@@ -1770,10 +1757,10 @@ void altivec_unavailable_tm(struct pt_regs *regs)
        TM_DEBUG("Vector Unavailable trap whilst transactional at 0x%lx,"
                 "MSR=%lx\n",
                 regs->nip, regs->msr);
-       tm_reclaim_current(TM_CAUSE_FAC_UNAV);
+       WARN_ON(MSR_TM_SUSPENDED(mfmsr()));
        current->thread.load_vec = 1;
-       tm_recheckpoint(&current->thread);
        current->thread.used_vr = 1;
+
 }
 
 void vsx_unavailable_tm(struct pt_regs *regs)
@@ -1792,12 +1779,11 @@ void vsx_unavailable_tm(struct pt_regs *regs)
        current->thread.used_vsr = 1;
 
        /* This reclaims FP and/or VR regs if they're already enabled */
-       tm_reclaim_current(TM_CAUSE_FAC_UNAV);
+       WARN_ON(MSR_TM_SUSPENDED(mfmsr()));
 
        current->thread.load_vec = 1;
        current->thread.load_fp = 1;
 
-       tm_recheckpoint(&current->thread);
 }
 #endif /* CONFIG_PPC_TRANSACTIONAL_MEM */
 
-- 
2.19.0