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Subject[PATCH 25/33] powerpc/64s/exception: remove lite interrupt return
Date
From: Nicholas Piggin <npiggin@gmail.com>

The difference between lite and regular returns is that the lite case
restores all NVGPRs, whereas lite skips that. This is quite clumsy
though, most interrupts want the NVGPRs saved for debugging, not to
modify in the caller, so the NVGPRs restore is not necessary most of
the time. Restore NVGPRs explicitly for one case that requires it,
and move everything else over to avoiding the restore unless the
interrupt return demands it (e.g., handling a signal).

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
arch/powerpc/kernel/entry_64.S | 4 ----
arch/powerpc/kernel/exceptions-64s.S | 21 +++++++++++----------
2 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index b2e68f5ca8f7..00173cc904ef 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -452,10 +452,6 @@ _GLOBAL(fast_interrupt_return)

.balign IFETCH_ALIGN_BYTES
_GLOBAL(interrupt_return)
- REST_NVGPRS(r1)
-
- .balign IFETCH_ALIGN_BYTES
-_GLOBAL(interrupt_return_lite)
ld r4,_MSR(r1)
andi. r0,r4,MSR_PR
beq kernel_interrupt_return
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 269edd1460be..1bccc869ebd3 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -1507,7 +1507,7 @@ EXC_COMMON_BEGIN(hardware_interrupt_common)
RUNLATCH_ON
addi r3,r1,STACK_FRAME_OVERHEAD
bl do_IRQ
- b interrupt_return_lite
+ b interrupt_return

GEN_KVM hardware_interrupt

@@ -1694,7 +1694,7 @@ EXC_COMMON_BEGIN(decrementer_common)
RUNLATCH_ON
addi r3,r1,STACK_FRAME_OVERHEAD
bl timer_interrupt
- b interrupt_return_lite
+ b interrupt_return

GEN_KVM decrementer

@@ -1785,7 +1785,7 @@ EXC_COMMON_BEGIN(doorbell_super_common)
#else
bl unknown_exception
#endif
- b interrupt_return_lite
+ b interrupt_return

GEN_KVM doorbell_super

@@ -2183,7 +2183,7 @@ EXC_COMMON_BEGIN(h_doorbell_common)
#else
bl unknown_exception
#endif
- b interrupt_return_lite
+ b interrupt_return

GEN_KVM h_doorbell

@@ -2213,7 +2213,7 @@ EXC_COMMON_BEGIN(h_virt_irq_common)
RUNLATCH_ON
addi r3,r1,STACK_FRAME_OVERHEAD
bl do_IRQ
- b interrupt_return_lite
+ b interrupt_return

GEN_KVM h_virt_irq

@@ -2260,7 +2260,7 @@ EXC_COMMON_BEGIN(performance_monitor_common)
RUNLATCH_ON
addi r3,r1,STACK_FRAME_OVERHEAD
bl performance_monitor_exception
- b interrupt_return_lite
+ b interrupt_return

GEN_KVM performance_monitor

@@ -3013,7 +3013,7 @@ do_hash_page:
cmpdi r3,0 /* see if __hash_page succeeded */

/* Success */
- beq interrupt_return_lite /* Return from exception on success */
+ beq interrupt_return /* Return from exception on success */

/* Error */
blt- 13f
@@ -3027,10 +3027,11 @@ do_hash_page:
handle_page_fault:
11: andis. r0,r5,DSISR_DABRMATCH@h
bne- handle_dabr_fault
+ bl save_nvgprs
addi r3,r1,STACK_FRAME_OVERHEAD
bl do_page_fault
cmpdi r3,0
- beq+ interrupt_return_lite
+ beq+ interrupt_return
mr r5,r3
addi r3,r1,STACK_FRAME_OVERHEAD
ld r4,_DAR(r1)
@@ -3045,9 +3046,9 @@ handle_dabr_fault:
bl do_break
/*
* do_break() may have changed the NV GPRS while handling a breakpoint.
- * If so, we need to restore them with their updated values. Don't use
- * interrupt_return_lite here.
+ * If so, we need to restore them with their updated values.
*/
+ REST_NVGPRS(r1)
b interrupt_return


--
2.23.0
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