[PATCH v6 05/12] powerpc: reverse the soft_enable logic

[Nicholas Piggin]

On Mon,  9 Jan 2017 19:06:11 +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 mask value "0x2"
> for "soft_enabled" to add support to mask PMIs. When ->soft_enabled is
> set to a value "3", PMI interrupts are mask and when set to a value
> of "1", PMI are not mask. With this patch also extends soft_enabled
> interrupt disable mask.
> 
> Signed-off-by: Madhavan Srinivasan <maddy at linux.vnet.ibm.com>

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