[PATCH 06/13] powerpc: reverse the soft_enable logic

[Madhavan Srinivasan]

On Friday 16 September 2016 03:35 PM, Nicholas Piggin wrote:
> On Thu, 15 Sep 2016 18:31:56 +0530
> Madhavan Srinivasan <maddy at linux.vnet.ibm.com> wrote:
>
>> "paca->soft_enabled" is used as a flag to mask some of interrupts.
>> Currently supported flags values and their details:
>>
>> soft_enabled    MSR[EE]
>>
>> 0               0       Disabled (PMI and HMI not masked)
>> 1               1       Enabled
>>
>> "paca->soft_enabled" is initialized to 1 to make the interripts as
>> enabled. arch_local_irq_disable() will toggle the value when interrupts
>> needs to disbled. At this point, the interrupts are not actually disabled,
>> instead, interrupt vector has code to check for the flag and mask it when it occurs.
>> By "mask it", it update interrupt paca->irq_happened and return.
>> arch_local_irq_restore() is called to re-enable interrupts, which checks and
>> replays interrupts if any occured.
>>
>> Now, as mentioned, current logic doesnot mask "performance monitoring interrupts"
>> and PMIs are implemented as NMI. But this patchset depends on local_irq_*
>> for a successful local_* update. Meaning, mask all possible interrupts during
>> local_* update and replay them after the update.
>>
>> So the idea here is to reserve the "paca->soft_enabled" logic. New values and
>> details:
>>
>> soft_enabled    MSR[EE]
>>
>> 1               0       Disabled  (PMI and HMI not masked)
>> 0               1       Enabled
>>
>> Reason for the this change is to create foundation for a third flag value "2"
>> for "soft_enabled" to add support to mask PMIs. When ->soft_enabled is
>> set to a value "2", PMI interrupts are mask and when set to a value
>> of "1", PMI are not mask.
>>
>> Signed-off-by: Madhavan Srinivasan <maddy at linux.vnet.ibm.com>
>> ---
>>   arch/powerpc/include/asm/hw_irq.h | 4 ++--
>>   arch/powerpc/kernel/entry_64.S    | 5 ++---
>>   2 files changed, 4 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h
>> index dc3c248f9244..fd9b421f9020 100644
>> --- a/arch/powerpc/include/asm/hw_irq.h
>> +++ b/arch/powerpc/include/asm/hw_irq.h
>> @@ -30,8 +30,8 @@
>>   /*
>>    * flags for paca->soft_enabled
>>    */
>> -#define IRQ_DISABLE_MASK_NONE		1
>> -#define IRQ_DISABLE_MASK_LINUX		0
>> +#define IRQ_DISABLE_MASK_NONE		0
>> +#define IRQ_DISABLE_MASK_LINUX		1
>>   
>>   #endif /* CONFIG_PPC64 */
>>   
>> diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
>> index aef7b64cbbeb..879aeb11ad29 100644
>> --- a/arch/powerpc/kernel/entry_64.S
>> +++ b/arch/powerpc/kernel/entry_64.S
>> @@ -131,8 +131,7 @@ END_FW_FTR_SECTION_IFSET(FW_FEATURE_SPLPAR)
>>   	 */
>>   #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_BUG)
>>   	lbz	r10,PACASOFTIRQEN(r13)
>> -	xori	r10,r10,IRQ_DISABLE_MASK_NONE
>> -1:	tdnei	r10,0
>> +1:	tdnei	r10,IRQ_DISABLE_MASK_NONE
>>   	EMIT_BUG_ENTRY 1b,__FILE__,__LINE__,BUGFLAG_WARNING
>>   #endif
>>   
>> @@ -1012,7 +1011,7 @@ _GLOBAL(enter_rtas)
>>   	 * check it with the asm equivalent of WARN_ON
>>   	 */
>>   	lbz	r0,PACASOFTIRQEN(r13)
>> -1:	tdnei	r0,IRQ_DISABLE_MASK_LINUX
>> +1:	tdeqi	r0,IRQ_DISABLE_MASK_NONE
>>   	EMIT_BUG_ENTRY 1b,__FILE__,__LINE__,BUGFLAG_WARNING
>>   #endif
>>   	
> We specifically want to ensure that _LINUX interrupts are disabled
> here. Not that we allow masking of others without _LINUX now, but
> current behavior is checking that LINUX ones are masked.
>
> Otherwise it seems okay.
>
> It might be nice after this series to do a pass and rename
> soft_enabled to soft_masked.

Yes definitely, I do have it in my todo.

Maddy

>
> Reviewed-by: Nicholas Piggin <npiggin at gmail.com>
>