linux-kernel - Re: [PATCH 0/8] Generic IRQ entry/exit support for powerpc

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Message-ID: <5b3923ca-fd0c-4093-87fc-67fbb9634705@linux.ibm.com>
Date: Fri, 21 Nov 2025 11:18:09 +0530
From: Mukesh Kumar Chaurasiya <mkchauras@...ux.ibm.com>
To: Thomas Gleixner <tglx@...utronix.de>,
        Shrikanth Hegde <sshegde@...ux.ibm.com>, maddy@...ux.ibm.com,
        mpe@...erman.id.au, npiggin@...il.com
Cc: christophe.leroy@...roup.eu, oleg@...hat.com, kees@...nel.org,
        luto@...capital.net, wad@...omium.org, mchauras@...ux.ibm.com,
        thuth@...hat.com, akpm@...ux-foundation.org, macro@...am.me.uk,
        ldv@...ace.io, deller@....de, charlie@...osinc.com,
        bigeasy@...utronix.de, segher@...nel.crashing.org,
        thomas.weissschuh@...utronix.de, menglong8.dong@...il.com,
        ankur.a.arora@...cle.com, peterz@...radead.org, namcao@...utronix.de,
        kan.liang@...ux.intel.com, mingo@...nel.org,
        atrajeev@...ux.vnet.ibm.com, mark.barnett@....com,
        coltonlewis@...gle.com, rppt@...nel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/8] Generic IRQ entry/exit support for powerpc


On 11/19/25 11:27 PM, Thomas Gleixner wrote:
> On Fri, Nov 07 2025 at 21:53, Shrikanth Hegde wrote:
>> On 11/2/25 5:23 PM, Mukesh Kumar Chaurasiya wrote:
>> diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
>> index ce59431f977c..c7cf9a3f1202 100644
>> --- a/arch/powerpc/kernel/interrupt.c
>> +++ b/arch/powerpc/kernel/interrupt.c
>> @@ -118,16 +118,18 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
>>                   regs->exit_flags |= _TIF_RESTOREALL;
>>           }
>>    
>> -again:
>> +       local_irq_disable();
>> +
>> +       user_exit_irqoff();
>>           syscall_exit_to_user_mode(regs);
>>    
>> -       user_enter_irqoff();
>> -       if (!prep_irq_for_enabled_exit(true)) {
>> -               user_exit_irqoff();
>> -               local_irq_enable();
>> -               local_irq_disable();
>> -               goto again;
>> -       }
>> +again:
>> +       if (!prep_irq_for_enabled_exit(true)) {
>> +               local_irq_enable();
>> +               local_irq_disable();
>> +               goto again;
>> +       }
>> +
> This does not look right at all.
>
>            syscall_exit_to_user_mode(regs)
>                  syscall_exit_to_user_mode_work()
>                  exit_to_user_mode()
>                     user_exit_irqoff()
yeah we also found an issue with context tracking here. I am working on 
fixing it.
>
> What you really want to do here is:
>
>   again:
> 	syscall_exit_to_user_mode_work(regs);
>   
> 	exit_to_user_mode(regs);
>   	if (!prep_irq_for_enabled_exit(true)) {
>          	// Re-establishes the full state required
>                  // to restart
> 		enter_from_user_mode(regs);
>   		local_irq_enable();
>   		local_irq_disable();
>   		goto again;
>
> That should cure it. Same issue in the other places.
This helps. Let me try this and i'll send a new version out as soon as 
we are done with testing.
> Thanks,
>
>          tglx

Thanks for the review.

Regards,

Mukesh