[PATCH][for 2.6.28] powerpc/fsl-booke: Fix problem with _tlbil_va being interrupted

[PATCH][for 2.6.28] powerpc/fsl-booke: Fix problem with _tlbil_va being interrupted

[Kumar Gala]

An example calling sequence which we did see:

copy_user_highpage -> kmap_atomic -> flush_tlb_page -> _tlbil_va

We got interrupted after setting up the MAS registers before the
tlbwe and the interrupt handler that caused the interrupt also did
a kmap_atomic (ide code) and thus on returning from the interrupt
the MAS registers no longer contained the proper values.

Since we dont save/restore MAS registers for normal interrupts we
need to disable interrupts in _tlbil_va to ensure atomicity.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
---
 arch/powerpc/kernel/misc_32.S |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S
index bdc8b0e..d108715 100644
--- a/arch/powerpc/kernel/misc_32.S
+++ b/arch/powerpc/kernel/misc_32.S
@@ -479,6 +479,8 @@ _GLOBAL(_tlbil_pid)
  * (no broadcast)
  */
 _GLOBAL(_tlbil_va)
+	mfmsr	r10
+	wrteei	0
 	slwi	r4,r4,16
 	mtspr	SPRN_MAS6,r4		/* assume AS=0 for now */
 	tlbsx	0,r3
@@ -490,6 +492,7 @@ _GLOBAL(_tlbil_va)
 	tlbwe
 	msync
 	isync
+	wrtee	r10
 	blr
 #endif /* CONFIG_FSL_BOOKE */
 
-- 
1.5.6.5

Re: [PATCH][for 2.6.28] powerpc/fsl-booke: Fix problem with _tlbil_va being interrupted

[Benjamin Herrenschmidt]

On Sat, 2008-12-13 at 17:33 -0600, Kumar Gala wrote:
> An example calling sequence which we did see:
> 
> copy_user_highpage -> kmap_atomic -> flush_tlb_page -> _tlbil_va
> 
> We got interrupted after setting up the MAS registers before the
> tlbwe and the interrupt handler that caused the interrupt also did
> a kmap_atomic (ide code) and thus on returning from the interrupt
> the MAS registers no longer contained the proper values.
> 
> Since we dont save/restore MAS registers for normal interrupts we
> need to disable interrupts in _tlbil_va to ensure atomicity.
> 
> Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---

Paul, this is a 2.6.28 regression, it should probably go to Linus in
case he hasn't released yet :-)

Cheers,
Ben.