Years ago, I fixed an R5000 O2 instability by implementing a workaround for

a chip bug, which was supposed to be fixed in that particular revision of
the die but wasn't (tlbhandler.S 1.16).

Being lazy, I did not write a runtime selection of the appropriate TLB
handler code, although this was on my list.

It turns out that this fix confuses the hell of R10000 processors revision 3
(but not earlier 2.x revisions), to the point of making the Origin 200 here
hang so hard it would not even enter the NMI handler (don't ask me how I
figured this was the cause).

So it's time to choose the appropriate TLB handling flavour at runtime,
building the trampoline code from the fixed exception handler location
jumping to the handler address at runtime. As a bonus, kernels linked in
KSEG0 get the address computation optimized and thus a smaller trampoline
than before.

1 files changed, 20 insertions, 55 deletions

diff --git a/sys/arch/mips64/mips64/tlbhandler.S b/sys/arch/mips64/mips64/tlbhandler.S
index c8141037618..3dce155233e 100644
--- a/sys/arch/mips64/mips64/tlbhandler.S
+++ b/sys/arch/mips64/mips64/tlbhandler.S
@@ -1,4 +1,4 @@
-/*	$OpenBSD: tlbhandler.S,v 1.17 2009/05/22 20:37:53 miod Exp $ */
+/*	$OpenBSD: tlbhandler.S,v 1.18 2009/05/25 17:10:38 miod Exp $ */
 
 /*
  * Copyright (c) 1995-2004 Opsycon AB  (www.opsycon.se / www.opsycon.com)
@@ -37,8 +37,6 @@
 #include <machine/regnum.h>
 #include <machine/cpustate.h>
 
-#define	HAIRY_R5000_ERRATA
-
 #include "assym.h"
 
 	.set	mips3
@@ -53,12 +51,11 @@
  *	available storage. If the startup code finds out that it
  *	is larger, the trampoline code is copied instead of panicing.
  */
-/*****************************  Start of code copied to exception vector */
-	.globl	tlb_miss	/* 0xffffffff80000000 */
 	.set	noat
-	.ent	tlb_miss, 0
-tlb_miss:
-#ifdef HAIRY_R5000_ERRATA
+
+	.globl	tlb_miss_err_r5k
+	.ent	tlb_miss_err_r5k, 0
+tlb_miss_err_r5k:
 	/*
 	 * R5000 errata: edge cases can trigger a TLB miss exception
 	 * instead of an invalid TLB exception. Servicing the TLB miss
@@ -75,12 +72,15 @@ tlb_miss:
 	 */
 	tlbp
 	mfc0	k1, COP_0_TLB_INDEX
-	bltz	k1, 1f			# missing!
+	bltz	k1, tlb_miss		# missing!
 	 nop
 	j	k_tlb_inv
 	 nop
-1:
-#endif
+	.end	tlb_miss_err_r5k
+
+	.globl	tlb_miss
+	.ent	tlb_miss, 0
+tlb_miss:
 	PTR_L	k1, curprocpaddr
 	dmfc0	k0, COP_0_BAD_VADDR
 	bltz	k0, _k_miss		# kernel address space
@@ -115,26 +115,24 @@ tlb_load:
 	eret				# RM7000 need 4 for JTLB usage.
 	.end	tlb_miss
 
-	.globl	e_tlb_miss
-e_tlb_miss:
-
 /*---------------------------------------------------------------- xtlb_miss
  *	Low level XTLB exception handler.
  */
-	.globl	xtlb_miss	/* 0xffffffff80000080 */
-	.set	noat
-	.ent	xtlb_miss, 0
-xtlb_miss:
-#ifdef HAIRY_R5000_ERRATA
+	.globl	xtlb_miss_err_r5k
+	.ent	xtlb_miss_err_r5k, 0
+xtlb_miss_err_r5k:
 	/* See errata comments in tlb_miss above */
 	tlbp
 	mfc0	k1, COP_0_TLB_INDEX
-	bltz	k1, 1f			# missing!
+	bltz	k1, xtlb_miss		# missing!
 	 nop
 	j	k_tlb_inv
 	 nop
-1:
-#endif
+	.end	xtlb_miss_err_r5k
+
+	.globl	xtlb_miss
+	.ent	xtlb_miss, 0
+xtlb_miss:
 	dmfc0	k0, COP_0_BAD_VADDR
 	bltz	k0, _k_miss		# kernel address space
 	PTR_SRL	k0, k0, SEGSHIFT
@@ -162,15 +160,9 @@ _k_miss:
 	dmfc0	k0, COP_0_BAD_VADDR	# must reload.
 	.end	xtlb_miss
 
-	.globl	e_xtlb_miss
-e_xtlb_miss:
-	.set	at
-/*****************************  End of code copied to exception vector */
-
 	.globl	tlb_miss_nopt
 	.ent	tlb_miss_nopt, 0
 tlb_miss_nopt:
-	.set	noat
 	mfc0	k0, COP_0_STATUS_REG
 	andi	k0, SR_KSU_USER
 	bne	k0, zero, go_u_general
@@ -178,35 +170,8 @@ tlb_miss_nopt:
 	j	k_general
 	nop
 	.end	tlb_miss_nopt
-	.set	at
 
-/*
- * Trampolines copied to exception vectors when code is too big.
- */
-	.globl	tlb_miss_tramp
-	.ent	tlb_miss_tramp, 0
-tlb_miss_tramp:
-	.set	noat
-	LA	k0, tlb_miss
-	jr	k0
-	nop
-	.end	tlb_miss_tramp
 	.set	at
-	.globl	e_tlb_miss_tramp
-e_tlb_miss_tramp:
-
-	.globl	xtlb_miss_tramp
-	.ent	xtlb_miss_tramp, 0
-xtlb_miss_tramp:
-	.set	noat
-	LA	k0, xtlb_miss
-	jr	k0
-	nop
-	.end	xtlb_miss_tramp
-	.set	at
-	.globl	e_xtlb_miss_tramp
-e_xtlb_miss_tramp:
-
 
 /*---------------------------------------------------------------- k_tlb_inv
  *	Handle a TLB invalid exception from kernel mode in kernel