[PATCH 00/13] powerpc: Backport 8xx TLB to 2.4

[Joakim Tjernlund]

Joakim Tjernlund/Transmode wrote on 2011/01/11 09:12:44:
>
> Willy Tarreau <w at 1wt.eu> wrote on 2011/01/11 07:09:26:
> >
> > Hi Joakim,
> >
> > On Mon, Jan 10, 2011 at 10:37:46PM +0100, Joakim Tjernlund wrote:
> > > This is a backport from 2.6 which I did to overcome 8xx CPU
> > > bugs. 8xx does not update the DAR register when taking a TLB
> > > error caused by dcbX and icbi insns which makes it very
> > > tricky to use these insns. Also the dcbst wrongly sets the
> > > the store bit when faulting into DTLB error.
> > > A few more bugs very found during development.
> > >
> > > I know 2.4 is in strict maintenance mode and 8xx is obsolete
> > > but as it is still in use I wanted 8xx to age with grace.
> >
> > Thank you very much for taking care of this, that's very much appreciated.
> > I'll look at this ASAP. Just a quick question in order to be certain, did
> > you have the opportunity to test all of these changes on real hardware ?

> I tested these on real 8xx HW but I used an older 2.4 linux as we haven't
> moved forward on 2.4 for quite some time.
> The affected files were almost identical though. Would be great if
> Scott could give them a spin on 8xx with current 2.4.

BTW, it occurred to me that the following 8xx quirk is best
done in 8xx code:

>From c1985a3b8b16d96ddce5ef90d5a15e70fb8a2aec Mon Sep 17 00:00:00 2001
From: Joakim Tjernlund <Joakim.Tjernlund at transmode.se>
Date: Tue, 11 Jan 2011 11:24:22 +0100
Subject: [PATCH] 8xx: Move invalidation of non present TLBs

8xx does not invalidate ~PRESENT TLBs, move the workaround
in mm/fault.c here to keep 8xx quirks localized.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund at transmode.se>
---
 arch/ppc/kernel/head_8xx.S |   12 ++++++++++--
 arch/ppc/mm/fault.c        |    7 -------
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/arch/ppc/kernel/head_8xx.S b/arch/ppc/kernel/head_8xx.S
index 75acaa0..24b206c 100644
--- a/arch/ppc/kernel/head_8xx.S
+++ b/arch/ppc/kernel/head_8xx.S
@@ -221,7 +221,11 @@ DataAccess:
 	mr	r5,r20
 	mfspr	r4,DAR
 	stw	r4,_DAR(r21)
-	li	r20,0x00f0
+	/* invalidate ~PRESENT TLBs, 8xx MMU don't do this */
+	andis.	r20,r5,0x4000
+	beq+	1f
+	tlbie	r4
+1:	li	r20,0x00f0
 	mtspr	DAR,r20	/* Tag DAR */
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	li	r20,MSR_KERNEL
@@ -238,7 +242,11 @@ InstructionAccess:
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	mr	r4,r22
 	mr	r5,r23
-	li	r20,MSR_KERNEL
+	/* invalidate ~PRESENT TLBs, 8xx MMU don't do this */
+	andis.	r20,r5,0x4000
+	beq+	1f
+	tlbie	r4
+1:	li	r20,MSR_KERNEL
 	rlwimi	r20,r23,0,16,16		/* copy EE bit from saved MSR */
 	FINISH_EXCEPTION(do_page_fault)

diff --git a/arch/ppc/mm/fault.c b/arch/ppc/mm/fault.c
index 874005a..8819fb1 100644
--- a/arch/ppc/mm/fault.c
+++ b/arch/ppc/mm/fault.c
@@ -116,13 +116,6 @@ void do_page_fault(struct pt_regs *regs, unsigned long address,
 	else
 		is_write = error_code & 0x02000000;
 #endif /* CONFIG_4xx || CONFIG_BOOKE */
-#if defined(CONFIG_8xx)
-	/* 8xx does no invalidate TLBs that are ~PRESENT,
-	 * do it here.
-	 */
-	if (error_code & 0x40000000)
-		_tlbie(address);
-#endif
 #if defined(CONFIG_XMON) || defined(CONFIG_KGDB)
 	if (debugger_fault_handler && regs->trap == 0x300) {
 		debugger_fault_handler(regs);
--
1.7.3.4

Scott, what do you think of this? Is it safe to call tlbie in this context?

    Jocke