Michael Ellerman wrote:
> "Naveen N. Rao" <naveen.n....@linux.vnet.ibm.com> writes:
>
>> On 2017/06/19 03:21PM, Aneesh Kumar K.V wrote:
>>> > @@ -1445,8 +1446,8 @@ do_hash_page:
>>> > handle_page_fault:
>>> > andis. r0,r4,DSISR_DABRMATCH@h
>>> > bne- handle_dabr_fault
>>> > - ld r4,_DAR(r1)
>>> > - ld r5,_DSISR(r1)
>>> > + mr r5,r4
>>> > + mr r4,r3
>>> > addi r3,r1,STACK_FRAME_OVERHEAD
>>> > bl do_page_fault
>>> > cmpdi r3,0
>>>
>>>
>>> Can we avoid that if we rearrange args of other functions calls, so that
>>> we can use r3 and r4 as it is ?
>>
>> Here's a version that does that. Again, boot tested with radix and
>> disable_radix.
>>
>> Thanks,
>> Naveen
>>
>> -
>> Change data_access_common() and instruction_access_common() to load the
>> trap number in r3, DAR in r4 and DSISR in r5 (rather than in r5, r3 and
>> r4 respectively). This change allows us to eliminate a few un-necessary
>> memory loads and register move operations in handle_page_fault(),
>> handle_dabr_fault() and label '77'.
>>
>> Signed-off-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
>> ---
>> arch/powerpc/kernel/exceptions-64s.S | 38
>> +++++++++++++++++-------------------
>> 1 file changed, 18 insertions(+), 20 deletions(-)
>
> Sorry I missed this and now it doesn't apply. Do you mind rebasing.
No problem - this is just a small refactoring after all :).
Here's a rebased version. Boot tested on mambo with/without radix.
Thanks,
Naveen
--
[PATCH v3] powerpc/exceptions64s: Eliminate a few un-necessary memory
loads
Change data_access_common() and instruction_access_common() to load the
trap number in r3, DAR in r4 and DSISR in r5 (rather than in r5, r3 and
r4 respectively). This change allows us to eliminate a few un-necessary
memory loads and register move operations in handle_page_fault(),
handle_dabr_fault() and label '77'.
Signed-off-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
---
arch/powerpc/kernel/exceptions-64s.S | 38 +++++++++++++++++-------------------
1 file changed, 18 insertions(+), 20 deletions(-)
diff --git a/arch/powerpc/kernel/exceptions-64s.S
b/arch/powerpc/kernel/exceptions-64s.S
index 72cffa0c4af6..b8166b4fa728 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -499,11 +499,11 @@ EXC_COMMON_BEGIN(data_access_common)
EXCEPTION_PROLOG_COMMON(0x300, PACA_EXGEN)
RECONCILE_IRQ_STATE(r10, r11)
ld r12,_MSR(r1)
- ld r3,PACA_EXGEN+EX_DAR(r13)
- lwz r4,PACA_EXGEN+EX_DSISR(r13)
- li r5,0x300
- std r3,_DAR(r1)
- std r4,_DSISR(r1)
+ ld r4,PACA_EXGEN+EX_DAR(r13)
+ lwz r5,PACA_EXGEN+EX_DSISR(r13)
+ li r3,0x300
+ std r4,_DAR(r1)
+ std r5,_DSISR(r1)
BEGIN_MMU_FTR_SECTION
b do_hash_page /* Try to handle as hpte fault */
MMU_FTR_SECTION_ELSE
@@ -543,11 +543,11 @@ EXC_COMMON_BEGIN(instruction_access_common)
EXCEPTION_PROLOG_COMMON(0x400, PACA_EXGEN)
RECONCILE_IRQ_STATE(r10, r11)
ld r12,_MSR(r1)
- ld r3,_NIP(r1)
- andis. r4,r12,DSISR_BAD_FAULT_64S@h
- li r5,0x400
- std r3,_DAR(r1)
- std r4,_DSISR(r1)
+ ld r4,_NIP(r1)
+ andis. r5,r12,DSISR_BAD_FAULT_64S@h
+ li r3,0x400
+ std r4,_DAR(r1)
+ std r5,_DSISR(r1)
BEGIN_MMU_FTR_SECTION
b do_hash_page /* Try to handle as hpte fault */
MMU_FTR_SECTION_ELSE
@@ -1523,7 +1523,7 @@ do_hash_page:
#ifdef CONFIG_PPC_BOOK3S_64
lis r0,DSISR_BAD_FAULT_64S@h
ori r0,r0,DSISR_BAD_FAULT_64S@l
- and. r0,r4,r0 /* weird error? */
+ and. r0,r5,r0 /* weird error? */
bne- handle_page_fault /* if not, try to insert a HPTE */
CURRENT_THREAD_INFO(r11, r1)
lwz r0,TI_PREEMPT(r11) /* If we're in an "NMI" */
@@ -1538,8 +1538,10 @@ do_hash_page:
*
* at return r3 = 0 for success, 1 for page fault, negative for error
*/
+ mr r6,r5
+ mr r5,r3
+ mr r3,r4
mr r4,r12
- ld r6,_DSISR(r1)
bl __hash_page /* build HPTE if possible */
cmpdi r3,0 /* see if __hash_page succeeded */
@@ -1549,16 +1551,15 @@ do_hash_page:
/* Error */
blt- 13f
- /* Reload DSISR into r4 for the DABR check below */
- ld r4,_DSISR(r1)
+ /* Reload DAR/DSISR for handle_page_fault */
+ ld r4,_DAR(r1)
+ ld r5,_DSISR(r1)
#endif /* CONFIG_PPC_BOOK3S_64 */
/* Here we have a page fault that hash_page can't handle. */
handle_page_fault:
-11: andis. r0,r4,DSISR_DABRMATCH@h
+ andis. r0,r5,DSISR_DABRMATCH@h
bne- handle_dabr_fault
- ld r4,_DAR(r1)
- ld r5,_DSISR(r1)
addi r3,r1,STACK_FRAME_OVERHEAD
bl do_page_fault
cmpdi r3,0
@@ -1573,8 +1574,6 @@ handle_page_fault:
/* We have a data breakpoint exception - handle it */
handle_dabr_fault:
bl save_nvgprs
- ld r4,_DAR(r1)
- ld r5,_DSISR(r1)
addi r3,r1,STACK_FRAME_OVERHEAD
bl do_break
12: b ret_from_except_lite
@@ -1600,7 +1599,6 @@ handle_dabr_fault:
* the access, or panic if there isn't a handler.
*/
77: bl save_nvgprs
- mr r4,r3
addi r3,r1,STACK_FRAME_OVERHEAD
li r5,SIGSEGV
bl bad_page_fault
--
2.15.0
