Re: [PATCH 5/7] riscv: mm: accelerate pagefault when badaccess

[Suren Baghdasaryan]

On Tue, Apr 2, 2024 at 12:53 AM Kefeng Wang  wrote:
>
> The vm_flags of vma already checked under per-VMA lock, if it is a
> bad access, directly handle error and return, there is no need to
> lock_mm_and_find_vma() and check vm_flags again.
>
> Signed-off-by: Kefeng Wang 

Reviewed-by: Suren Baghdasaryan 

> ---
>  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;
> +   bad_area_nosemaphore(regs, code, addr);
> +   return;
> }
>
> fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
> --
> 2.27.0
>

[PATCH 5/7] riscv: mm: accelerate pagefault when badaccess

[Kefeng Wang]

The vm_flags of vma already checked under per-VMA lock, if it is a
bad access, directly handle error and return, there is no need to
lock_mm_and_find_vma() and check vm_flags again.

Signed-off-by: Kefeng Wang 
---
 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;
+   bad_area_nosemaphore(regs, code, addr);
+   return;
}
 
fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
-- 
2.27.0