linux-kernel - Re: [PATCH -next v4 04/19] arm64: entry: Remove __enter_from_kernel

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Message-ID: <49e78df6-91bf-7c63-b2d0-f36a301535da@huawei.com>
Date: Thu, 31 Oct 2024 11:56:25 +0800
From: Jinjie Ruan <ruanjinjie@...wei.com>
To: Mark Rutland <mark.rutland@....com>
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Subject: Re: [PATCH -next v4 04/19] arm64: entry: Remove
 __enter_from_kernel_mode()



On 2024/10/29 22:37, Mark Rutland wrote:
> On Fri, Oct 25, 2024 at 06:06:45PM +0800, Jinjie Ruan wrote:
>> The __enter_from_kernel_mode() is only called by enter_from_kernel_mode(),
>> remove it.
> 
> The point of this split is to cleanly separate the raw entry logic (in
> __enter_from_kernel_mode() from pieces that run later and can safely be
> instrumented (later in enter_from_kernel_mode()).

Hi, Mark,

I reviewed your commit bc29b71f53b1 ("arm64: entry: clarify entry/exit
helpers"), and keep these functions is to make instrumentation
boundaries more clear, and will not change them.

> 
> I had expected that a later patch would replace
> __enter_from_kernel_mode() with the generic equivalent, leaving
> enter_from_kernel_mode() unchanged. It looks like patch 16 could do that
> without this patch being necessary -- am I missing something?

Yes, you are right! these useless cleanup patches will be removed.

And when switched to generic syscall, I found that proper refactoring
would also facilitate clear code switching.

Thank you.

> 
> Mark.
> 
>>
>> No functional changes.
>>
>> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
>> ---
>>  arch/arm64/kernel/entry-common.c | 9 +--------
>>  1 file changed, 1 insertion(+), 8 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
>> index ccf59b44464d..a7fd4d6c7650 100644
>> --- a/arch/arm64/kernel/entry-common.c
>> +++ b/arch/arm64/kernel/entry-common.c
>> @@ -36,7 +36,7 @@
>>   * This is intended to match the logic in irqentry_enter(), handling the kernel
>>   * mode transitions only.
>>   */
>> -static __always_inline irqentry_state_t __enter_from_kernel_mode(struct pt_regs *regs)
>> +static noinstr irqentry_state_t enter_from_kernel_mode(struct pt_regs *regs)
>>  {
>>  	irqentry_state_t ret = {
>>  		.exit_rcu = false,
>> @@ -55,13 +55,6 @@ static __always_inline irqentry_state_t __enter_from_kernel_mode(struct pt_regs
>>  	rcu_irq_enter_check_tick();
>>  	trace_hardirqs_off_finish();
>>  
>> -	return ret;
>> -}
>> -
>> -static noinstr irqentry_state_t enter_from_kernel_mode(struct pt_regs *regs)
>> -{
>> -	irqentry_state_t ret = __enter_from_kernel_mode(regs);
>> -
>>  	mte_check_tfsr_entry();
>>  	mte_disable_tco_entry(current);
>>  
>> -- 
>> 2.34.1
>>
>