When the dst buffer pointer points to the last accessible aligned addr, we
could still run another iteration of unrolled copy.
Signed-off-by: Xiao Wang <[email protected]>
---
arch/riscv/lib/uaccess.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/riscv/lib/uaccess.S b/arch/riscv/lib/uaccess.S
index 2e665f8f8fcc..1399d797d81b 100644
--- a/arch/riscv/lib/uaccess.S
+++ b/arch/riscv/lib/uaccess.S
@@ -103,7 +103,7 @@ SYM_FUNC_START(fallback_scalar_usercopy)
fixup REG_S t4, 7*SZREG(a0), 10f
addi a0, a0, 8*SZREG
addi a1, a1, 8*SZREG
- bltu a0, t0, 2b
+ bleu a0, t0, 2b
addi t0, t0, 8*SZREG /* revert to original value */
j .Lbyte_copy_tail
--
2.25.1
Hi Xiao,
On 13/03/2024 11:33, Xiao Wang wrote:
> When the dst buffer pointer points to the last accessible aligned addr, we
> could still run another iteration of unrolled copy.
>
> Signed-off-by: Xiao Wang <[email protected]>
> ---
> arch/riscv/lib/uaccess.S | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/riscv/lib/uaccess.S b/arch/riscv/lib/uaccess.S
> index 2e665f8f8fcc..1399d797d81b 100644
> --- a/arch/riscv/lib/uaccess.S
> +++ b/arch/riscv/lib/uaccess.S
> @@ -103,7 +103,7 @@ SYM_FUNC_START(fallback_scalar_usercopy)
> fixup REG_S t4, 7*SZREG(a0), 10f
> addi a0, a0, 8*SZREG
> addi a1, a1, 8*SZREG
> - bltu a0, t0, 2b
> + bleu a0, t0, 2b
>
> addi t0, t0, 8*SZREG /* revert to original value */
> j .Lbyte_copy_tail
I agree it is still safe to continue for another word_copy here.
Reviewed-by: Alexandre Ghiti <[email protected]>
Thanks,
Alex
Hi Ben,
On 03/05/2024 14:19, Ben Dooks wrote:
> On 03/05/2024 13:16, Alexandre Ghiti wrote:
>> Hi Xiao,
>>
>> On 13/03/2024 11:33, Xiao Wang wrote:
>>> When the dst buffer pointer points to the last accessible aligned
>>> addr, we
>>> could still run another iteration of unrolled copy.
>>>
>>> Signed-off-by: Xiao Wang <[email protected]>
>>> ---
>>> arch/riscv/lib/uaccess.S | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/arch/riscv/lib/uaccess.S b/arch/riscv/lib/uaccess.S
>>> index 2e665f8f8fcc..1399d797d81b 100644
>>> --- a/arch/riscv/lib/uaccess.S
>>> +++ b/arch/riscv/lib/uaccess.S
>>> @@ -103,7 +103,7 @@ SYM_FUNC_START(fallback_scalar_usercopy)
>>> fixup REG_S t4, 7*SZREG(a0), 10f
>>> addi a0, a0, 8*SZREG
>>> addi a1, a1, 8*SZREG
>>> - bltu a0, t0, 2b
>>> + bleu a0, t0, 2b
>>> addi t0, t0, 8*SZREG /* revert to original value */
>>> j .Lbyte_copy_tail
>>
>>
>> I agree it is still safe to continue for another word_copy here.
>>
>> Reviewed-by: Alexandre Ghiti <[email protected]>
>
> Out of interest, has anyone checked if causing a schedule event during
> this code breaks like the last time we had issues with the upstream
> testing?
I vaguely remember something, do you have a link to that discussion by
chance?
>
> I did propose saving the state of the user-access flag in the task
> struct
Makes sense, I just took a quick look and SR_SUM is cleared as soon as
we enter handle_exception() and it does not seem to be restored. Weird
it works, unless I missed something!
> but we mostly solved it by making sleeping functions stay
> away from the address calculation. This of course may have been done
> already or need to be done if three's long areas where the user-access
> flags can be disabled (generally only a few drivers did this, so we
> may not have come across the problem)
>
I don't understand what you mean here, would you mind expanding a bit?
Thanks,
Alex
Hello:
This patch was applied to riscv/linux.git (for-next)
by Palmer Dabbelt <[email protected]>:
On Wed, 13 Mar 2024 18:33:34 +0800 you wrote:
> When the dst buffer pointer points to the last accessible aligned addr, we
> could still run another iteration of unrolled copy.
>
> Signed-off-by: Xiao Wang <[email protected]>
> ---
> arch/riscv/lib/uaccess.S | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
Here is the summary with links:
- riscv: uaccess: Allow the last potential unrolled copy
https://git.kernel.org/riscv/c/74362d66a416
You are awesome, thank you!
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