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

On Friday 16 September 2016 03:35 PM, Nicholas Piggin wrote:

On Thu, 15 Sep 2016 18:31:56 +0530
Madhavan Srinivasan [off-list ref] wrote:

quoted

"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 <redacted>
---
  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@gmail.com>