powerpc: Call do_page_fault() with interrupts off
We currently turn interrupts back to their previous state before
calling do_page_fault(). This can be annoying when debugging as
a bad fault will potentially have lost some processor state before
getting into the debugger.
We also end up calling some generic code with interrupts enabled
such as notify_page_fault() with interrupts enabled, which could
be unexpected.
This changes our code to behave more like other architectures,
and make the assembly entry code call into do_page_faults() with
interrupts disabled. They are conditionally re-enabled from
within do_page_fault() in the same spot x86 does it.
While there, add the might_sleep() test in the case of a successful
trylock of the mmap semaphore, again like x86.
Also fix a bug in the existing assembly where r12 (_MSR) could get
clobbered by C calls (the DTL accounting in the exception common
macro and DISABLE_INTS) in some cases.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
v2. Add the r12 clobber fix
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 3af80e8..d8ff6d3 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -559,6 +559,8 @@
mfspr r10,SPRN_DSISR
stw r10,PACA_EXGEN+EX_DSISR(r13)
EXCEPTION_PROLOG_COMMON(0x300, PACA_EXGEN)
+ DISABLE_INTS
+ ld r12,_MSR(r1)
ld r3,PACA_EXGEN+EX_DAR(r13)
lwz r4,PACA_EXGEN+EX_DSISR(r13)
li r5,0x300
@@ -573,6 +575,7 @@
stw r10,PACA_EXGEN+EX_DSISR(r13)
EXCEPTION_PROLOG_COMMON(0xe00, PACA_EXGEN)
bl .save_nvgprs
+ DISABLE_INTS
addi r3,r1,STACK_FRAME_OVERHEAD
bl .unknown_exception
b .ret_from_except
@@ -581,6 +584,8 @@
.globl instruction_access_common
instruction_access_common:
EXCEPTION_PROLOG_COMMON(0x400, PACA_EXGEN)
+ DISABLE_INTS
+ ld r12,_MSR(r1)
ld r3,_NIP(r1)
andis. r4,r12,0x5820
li r5,0x400
@@ -884,24 +889,6 @@
lwz r0,TI_PREEMPT(r11) /* If we're in an "NMI" */
andis. r0,r0,NMI_MASK@h /* (i.e. an irq when soft-disabled) */
bne 77f /* then don't call hash_page now */
-
- /* We run with interrupts both soft and hard disabled */
- DISABLE_INTS
-
- /*
- * Currently, trace_hardirqs_off() will be called by DISABLE_INTS
- * and will clobber volatile registers when irq tracing is enabled
- * so we need to reload them. It may be possible to be smarter here
- * and move the irq tracing elsewhere but let's keep it simple for
- * now
- */
-#ifdef CONFIG_TRACE_IRQFLAGS
- ld r3,_DAR(r1)
- ld r4,_DSISR(r1)
- ld r5,_TRAP(r1)
- ld r12,_MSR(r1)
- clrrdi r5,r5,4
-#endif /* CONFIG_TRACE_IRQFLAGS */
/*
* We need to set the _PAGE_USER bit if MSR_PR is set or if we are
* accessing a userspace segment (even from the kernel). We assume
@@ -931,17 +918,22 @@
beq fast_exc_return_irq /* Return from exception on success */
/* For a hash failure, we don't bother re-enabling interrupts */
- ble- 12f
+ ble- 13f
- /*
- * hash_page couldn't handle it, set soft interrupt enable back
- * to what it was before the trap. Note that .arch_local_irq_restore
- * handles any interrupts pending at this point.
- */
- ld r3,SOFTE(r1)
- TRACE_AND_RESTORE_IRQ_PARTIAL(r3, 11f)
- bl .arch_local_irq_restore
- b 11f
+/* Here we have a page fault that hash_page can't handle. */
+handle_page_fault:
+11: ld r4,_DAR(r1)
+ ld r5,_DSISR(r1)
+ addi r3,r1,STACK_FRAME_OVERHEAD
+ bl .do_page_fault
+ cmpdi r3,0
+ beq+ 12f
+ bl .save_nvgprs
+ mr r5,r3
+ addi r3,r1,STACK_FRAME_OVERHEAD
+ lwz r4,_DAR(r1)
+ bl .bad_page_fault
+ b .ret_from_except
/* We have a data breakpoint exception - handle it */
handle_dabr_fault:
@@ -950,30 +942,13 @@
ld r5,_DSISR(r1)
addi r3,r1,STACK_FRAME_OVERHEAD
bl .do_dabr
- b .ret_from_except_lite
+12: b .ret_from_except_lite
-/* Here we have a page fault that hash_page can't handle. */
-handle_page_fault:
- ENABLE_INTS
-11: ld r4,_DAR(r1)
- ld r5,_DSISR(r1)
- addi r3,r1,STACK_FRAME_OVERHEAD
- bl .do_page_fault
- cmpdi r3,0
- beq+ 13f
- bl .save_nvgprs
- mr r5,r3
- addi r3,r1,STACK_FRAME_OVERHEAD
- lwz r4,_DAR(r1)
- bl .bad_page_fault
- b .ret_from_except
-
-13: b .ret_from_except_lite
/* We have a page fault that hash_page could handle but HV refused
* the PTE insertion
*/
-12: bl .save_nvgprs
+13: bl .save_nvgprs
mr r5,r3
addi r3,r1,STACK_FRAME_OVERHEAD
ld r4,_DAR(r1)