[PATCH v2 5/7] riscv: mm: accelerate pagefault when badaccess
Kefeng Wang
wangkefeng.wang at huawei.com
Wed Apr 10 01:07:41 PDT 2024
On 2024/4/10 15:32, Alexandre Ghiti wrote:
> Hi Kefeng,
>
> On 03/04/2024 10:38, Kefeng Wang wrote:
>> The access_error() of vma already checked under per-VMA lock, if it
>> is a bad access, directly handle error, no need to retry with mmap_lock
>> again. Since the page faut is handled under per-VMA lock, count it as
>> a vma lock event with VMA_LOCK_SUCCESS.
>>
>> Reviewed-by: Suren Baghdasaryan <surenb at google.com>
>> Signed-off-by: Kefeng Wang <wangkefeng.wang at huawei.com>
>> ---
>> arch/riscv/mm/fault.c | 5 ++++-
>> 1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
>> index 3ba1d4dde5dd..b3fcf7d67efb 100644
>> --- a/arch/riscv/mm/fault.c
>> +++ b/arch/riscv/mm/fault.c
>> @@ -292,7 +292,10 @@ void handle_page_fault(struct pt_regs *regs)
>> if (unlikely(access_error(cause, vma))) {
>> vma_end_read(vma);
>> - goto lock_mmap;
>> + count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
>> + tsk->thread.bad_cause = SEGV_ACCERR;
>
>
> I think we should use the cause variable here instead of SEGV_ACCERR, as
> bad_cause is a riscv internal status which describes the real fault that
> happened.
Oh, I see, it is exception causes on riscv, so it should be
diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
index b3fcf7d67efb..5224f3733802 100644
--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -293,8 +293,8 @@ void handle_page_fault(struct pt_regs *regs)
if (unlikely(access_error(cause, vma))) {
vma_end_read(vma);
count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
- tsk->thread.bad_cause = SEGV_ACCERR;
- bad_area_nosemaphore(regs, code, addr);
+ tsk->thread.bad_cause = cause;
+ bad_area_nosemaphore(regs, SEGV_ACCERR, addr);
return;
}
Hi Alex, could you help to check it?
Hi Andrew, please help to squash it after Alex ack it.
Thanks both.
>
> Thanks,
>
> Alex
>
>
>> + bad_area_nosemaphore(regs, code, addr);
>> + return;
>> }
>> fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK,
>> regs);
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