[PATCH] powerpc/8xx: Fix software emulation interrupt

For unimplemented instructions or unimplemented SPRs, the 8xx triggers
a "Software Emulation Exception" (0x1000). That interrupt doesn't set
reason bits in SRR1 as the "Program Check Exception" does.

Go through emulation_assist_interrupt() to set REASON_ILLEGAL.

Fixes: fbbcc3bb139e ("powerpc/8xx: Remove SoftwareEmulation()")
Signed-off-by: Christophe Leroy <redacted>
---
I'm wondering whether it wouldn't be better to set REASON_ILLEGAL
in the exception prolog and still call program_check_exception.
And do the same in book3s/64 to avoid the nightmare of an
INTERRUPT_HANDLER calling another INTERRUPT_HANDLER.
---
 arch/powerpc/kernel/head_8xx.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 52702f3db6df..9eb63cf6ac38 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S

@@ -165,7 +165,7 @@ SystemCall:
 /* On the MPC8xx, this is a software emulation interrupt.  It occurs
  * for all unimplemented and illegal instructions.
  */
-	EXCEPTION(0x1000, SoftEmu, program_check_exception, EXC_XFER_STD)
+	EXCEPTION(0x1000, SoftEmu, emulation_assist_interrupt, EXC_XFER_STD)
 
 	. = 0x1100
 /*

-- 
2.25.0

Excerpts from Christophe Leroy's message of February 5, 2021 6:56 pm:

For unimplemented instructions or unimplemented SPRs, the 8xx triggers
a "Software Emulation Exception" (0x1000). That interrupt doesn't set
reason bits in SRR1 as the "Program Check Exception" does.

Go through emulation_assist_interrupt() to set REASON_ILLEGAL.

Fixes: fbbcc3bb139e ("powerpc/8xx: Remove SoftwareEmulation()")
Signed-off-by: Christophe Leroy <redacted>
---
I'm wondering whether it wouldn't be better to set REASON_ILLEGAL
in the exception prolog and still call program_check_exception.
And do the same in book3s/64 to avoid the nightmare of an
INTERRUPT_HANDLER calling another INTERRUPT_HANDLER.

Hmm, I missed this. We just change program_check_exception to
a common function which is called by both.

Thanks,
Nick

On Fri, 5 Feb 2021 08:56:13 +0000 (UTC), Christophe Leroy wrote:

For unimplemented instructions or unimplemented SPRs, the 8xx triggers
a "Software Emulation Exception" (0x1000). That interrupt doesn't set
reason bits in SRR1 as the "Program Check Exception" does.

Go through emulation_assist_interrupt() to set REASON_ILLEGAL.

Applied to powerpc/next.

[1/1] powerpc/8xx: Fix software emulation interrupt
      https://git.kernel.org/powerpc/c/903178d0ce6bb30ef80a3604ab9ee2b57869fbc9

cheers