[RFC PATCH 02/12] powerpc: remove arguments from interrupt handler functions

[Christophe Leroy]

On Mon, 2020-09-07 at 11:20 +0200, Christophe Leroy wrote:
> 
> Le 05/09/2020 à 19:43, Nicholas Piggin a écrit :
> > Make interrupt handlers all just take the pt_regs * argument and load
> > DAR/DSISR etc from that. Make those that return a value return long.
> 
> I like this, it will likely simplify a bit the VMAP_STACK mess.
> 
> Not sure it is that easy. My board is stuck after the start of init.
> 
> 
> On the 8xx, on Instruction TLB Error exception, we do
> 
> 	andis.	r5,r9,DSISR_SRR1_MATCH_32S at h /* Filter relevant SRR1 bits */
> 
> On book3s/32, on ISI exception we do:
> 	andis.	r5,r9,DSISR_SRR1_MATCH_32S at h /* Filter relevant SRR1 bits */
> 
> On 40x and bookE, on ISI exception we do:
> 	li	r5,0			/* Pass zero as arg3 */
> 
> 
> And regs->dsisr will just contain nothing
> 
> So it means we should at least write back r5 into regs->dsisr from there 
> ? The performance impact should be minimal as we already write _DAR so 
> the cache line should already be in the cache.
> 
> A hacky 'stw r5, _DSISR(r1)' in handle_page_fault() does the trick, 
> allthough we don't want to do it for both ISI and DSI at the end, so 
> you'll have to do it in every head_xxx.S

To get you series build and work, I did the following hacks:

diff --git a/arch/powerpc/include/asm/interrupt.h
b/arch/powerpc/include/asm/interrupt.h
index acfcc7d5779b..c11045d3113a 100644
--- a/arch/powerpc/include/asm/interrupt.h
+++ b/arch/powerpc/include/asm/interrupt.h
@@ -93,7 +93,9 @@ static inline void interrupt_nmi_exit_prepare(struct
pt_regs *regs, struct inter
 {
 	nmi_exit();
 
+#ifdef CONFIG_PPC64
 	this_cpu_set_ftrace_enabled(state->ftrace_enabled);
+#endif
 
 #ifdef CONFIG_PPC_BOOK3S_64
 	/* Check we didn't change the pending interrupt mask. */
diff --git a/arch/powerpc/kernel/entry_32.S
b/arch/powerpc/kernel/entry_32.S
index f4d0af8e1136..66f7adbe1076 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -663,6 +663,7 @@ ppc_swapcontext:
  */
 	.globl	handle_page_fault
 handle_page_fault:
+	stw	r5,_DSISR(r1)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 #ifdef CONFIG_PPC_BOOK3S_32
 	andis.  r0,r5,DSISR_DABRMATCH at h
---

Christophe