Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=00efee7d5d0d7888aafbf0d2de76943ee8aca47a
Commit: 00efee7d5d0d7888aafbf0d2de76943ee8aca47a
Parent: 61a564fd2e7ab13ab11a6ce8305433baacf344ef
Author: Michael Neuling <[EMAIL PROTECTED]>
AuthorDate: Fri Aug 24 16:58:37 2007 +1000
Committer: Paul Mackerras <[EMAIL PROTECTED]>
CommitDate: Wed Sep 19 14:40:54 2007 +1000
[POWERPC] Remove barriers from the SLB shadow buffer update
After talking to an IBM POWER hypervisor (PHYP) design and development
guy, there seems to be no need for memory barriers when updating the SLB
shadow buffer provided we only update it from the current CPU, which we
do.
Also, these guys see no need in the future for these barriers.
Signed-off-by: Michael Neuling <[EMAIL PROTECTED]>
Signed-off-by: Paul Mackerras <[EMAIL PROTECTED]>
---
arch/powerpc/kernel/entry_64.S | 8 ++++----
arch/powerpc/mm/slb.c | 6 ++----
2 files changed, 6 insertions(+), 8 deletions(-)
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 952eba6..fbbd3f6 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -385,15 +385,15 @@ BEGIN_FTR_SECTION
oris r0,r6,(SLB_ESID_V)@h
ori r0,r0,(SLB_NUM_BOLTED-1)@l
- /* Update the last bolted SLB */
+ /* Update the last bolted SLB. No write barriers are needed
+ * here, provided we only update the current CPU's SLB shadow
+ * buffer.
+ */
ld r9,PACA_SLBSHADOWPTR(r13)
li r12,0
std r12,SLBSHADOW_STACKESID(r9) /* Clear ESID */
- eieio
std r7,SLBSHADOW_STACKVSID(r9) /* Save VSID */
- eieio
std r0,SLBSHADOW_STACKESID(r9) /* Save ESID */
- eieio
slbie r6
slbie r6 /* Workaround POWER5 < DD2.1 issue */
diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c
index ff1811a..4bee1cf 100644
--- a/arch/powerpc/mm/slb.c
+++ b/arch/powerpc/mm/slb.c
@@ -59,14 +59,12 @@ static inline void slb_shadow_update(unsigned long ea,
{
/*
* Clear the ESID first so the entry is not valid while we are
- * updating it.
+ * updating it. No write barriers are needed here, provided
+ * we only update the current CPU's SLB shadow buffer.
*/
get_slb_shadow()->save_area[entry].esid = 0;
- smp_wmb();
get_slb_shadow()->save_area[entry].vsid = mk_vsid_data(ea, flags);
- smp_wmb();
get_slb_shadow()->save_area[entry].esid = mk_esid_data(ea, entry);
- smp_wmb();
}
static inline void slb_shadow_clear(unsigned long entry)
-
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