Le 08/09/2020 à 10:29, Christophe Leroy a écrit :
Le 08/09/2020 à 09:48, Nicholas Piggin a écrit :
Excerpts from Christophe Leroy's message of September 7, 2020 9:34 pm:
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@h /* Filter relevant SRR1
bits */
On book3s/32, on ISI exception we do:
andis. r5,r9,DSISR_SRR1_MATCH_32S@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:
Great, thanks for this.
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
This seems okay, not a hack.
#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@h
Is this what you want to do for 32, or do you want to seperate
ISI and DSI sides?
No I think we want to separate ISI and DSI sides.
And I think the specific filtering done in ISI could be done in
do_page_fault() in C. Ok, it would make a special handling for is_exec
but there are already several places where the behaviour differs based
on is_exec.
The only thing we need to keep at ASM level is the DABR stuff for
calling do_break() in handle_page_fault(), because it is used to decide
whether full regs are saved or not. But it could be a test done earlier
in the prolog and the result being kept in one of the CR bits.
Looking at it once more, I'm wondering whether we really need a full regs.
Before commit
https://github.com/linuxppc/linux/commit/d300627c6a53693fb01479b59b0cdd293761b1fa#diff-f9658f412252f3bb3093e0a95b37f3ac
do_break() was called from do_page_fault() without a full regs set.
Christophe
