This is a note to let you know that I've just added the patch titled
powerpc/tm: Switch out userspace PPR and DSCR sooner
to the 3.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-tm-switch-out-userspace-ppr-and-dscr-sooner.patch
and it can be found in the queue-3.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e9bdc3d6143d1c4b8d8ce5231fc958268331f983 Mon Sep 17 00:00:00 2001
From: Michael Neuling <mikey@xxxxxxxxxxx>
Date: Thu, 26 Sep 2013 13:29:09 +1000
Subject: powerpc/tm: Switch out userspace PPR and DSCR sooner
From: Michael Neuling <mikey@xxxxxxxxxxx>
commit e9bdc3d6143d1c4b8d8ce5231fc958268331f983 upstream.
When we do a treclaim or trecheckpoint we end up running with userspace
PPR and DSCR values. Currently we don't do anything special to avoid
running with user values which could cause a severe performance
degradation.
This patch moves the PPR and DSCR save and restore around treclaim and
trecheckpoint so that we run with user values for a much shorter period.
More care is taken with the PPR as it's impact is greater than the DSCR.
This is similar to user exceptions, where we run HTM_MEDIUM early to
ensure that we don't run with a userspace PPR values in the kernel.
Signed-off-by: Michael Neuling <mikey@xxxxxxxxxxx>
Signed-off-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kernel/tm.S | 94 +++++++++++++++++++++++++++++++----------------
1 file changed, 63 insertions(+), 31 deletions(-)
--- a/arch/powerpc/kernel/tm.S
+++ b/arch/powerpc/kernel/tm.S
@@ -79,6 +79,11 @@ _GLOBAL(tm_abort)
TABORT(R3)
blr
+ .section ".toc","aw"
+DSCR_DEFAULT:
+ .tc dscr_default[TC],dscr_default
+
+ .section ".text"
/* void tm_reclaim(struct thread_struct *thread,
* unsigned long orig_msr,
@@ -187,11 +192,18 @@ dont_backup_fp:
std r1, PACATMSCRATCH(r13)
ld r1, PACAR1(r13)
+ /* Store the PPR in r11 and reset to decent value */
+ std r11, GPR11(r1) /* Temporary stash */
+ mfspr r11, SPRN_PPR
+ HMT_MEDIUM
+
/* Now get some more GPRS free */
std r7, GPR7(r1) /* Temporary stash */
std r12, GPR12(r1) /* '' '' '' */
ld r12, STACK_PARAM(0)(r1) /* Param 0, thread_struct * */
+ std r11, THREAD_TM_PPR(r12) /* Store PPR and free r11 */
+
addi r7, r12, PT_CKPT_REGS /* Thread's ckpt_regs */
/* Make r7 look like an exception frame so that we
@@ -203,15 +215,19 @@ dont_backup_fp:
SAVE_GPR(0, r7) /* user r0 */
SAVE_GPR(2, r7) /* user r2 */
SAVE_4GPRS(3, r7) /* user r3-r6 */
- SAVE_4GPRS(8, r7) /* user r8-r11 */
+ SAVE_GPR(8, r7) /* user r8 */
+ SAVE_GPR(9, r7) /* user r9 */
+ SAVE_GPR(10, r7) /* user r10 */
ld r3, PACATMSCRATCH(r13) /* user r1 */
ld r4, GPR7(r1) /* user r7 */
- ld r5, GPR12(r1) /* user r12 */
- GET_SCRATCH0(6) /* user r13 */
+ ld r5, GPR11(r1) /* user r11 */
+ ld r6, GPR12(r1) /* user r12 */
+ GET_SCRATCH0(8) /* user r13 */
std r3, GPR1(r7)
std r4, GPR7(r7)
- std r5, GPR12(r7)
- std r6, GPR13(r7)
+ std r5, GPR11(r7)
+ std r6, GPR12(r7)
+ std r8, GPR13(r7)
SAVE_NVGPRS(r7) /* user r14-r31 */
@@ -234,14 +250,12 @@ dont_backup_fp:
std r6, _XER(r7)
- /* ******************** TAR, PPR, DSCR ********** */
+ /* ******************** TAR, DSCR ********** */
mfspr r3, SPRN_TAR
- mfspr r4, SPRN_PPR
- mfspr r5, SPRN_DSCR
+ mfspr r4, SPRN_DSCR
std r3, THREAD_TM_TAR(r12)
- std r4, THREAD_TM_PPR(r12)
- std r5, THREAD_TM_DSCR(r12)
+ std r4, THREAD_TM_DSCR(r12)
/* MSR and flags: We don't change CRs, and we don't need to alter
* MSR.
@@ -258,7 +272,7 @@ dont_backup_fp:
std r3, THREAD_TM_TFHAR(r12)
std r4, THREAD_TM_TFIAR(r12)
- /* AMR and PPR are checkpointed too, but are unsupported by Linux. */
+ /* AMR is checkpointed too, but is unsupported by Linux. */
/* Restore original MSR/IRQ state & clear TM mode */
ld r14, TM_FRAME_L0(r1) /* Orig MSR */
@@ -274,6 +288,12 @@ dont_backup_fp:
mtcr r4
mtlr r0
ld r2, 40(r1)
+
+ /* Load system default DSCR */
+ ld r4, DSCR_DEFAULT@toc(r2)
+ ld r0, 0(r4)
+ mtspr SPRN_DSCR, r0
+
blr
@@ -358,25 +378,24 @@ dont_restore_fp:
restore_gprs:
- /* ******************** TAR, PPR, DSCR ********** */
- ld r4, THREAD_TM_TAR(r3)
- ld r5, THREAD_TM_PPR(r3)
- ld r6, THREAD_TM_DSCR(r3)
+ /* ******************** CR,LR,CCR,MSR ********** */
+ ld r4, _CTR(r7)
+ ld r5, _LINK(r7)
+ ld r6, _CCR(r7)
+ ld r8, _XER(r7)
+
+ mtctr r4
+ mtlr r5
+ mtcr r6
+ mtxer r8
+ /* ******************** TAR ******************** */
+ ld r4, THREAD_TM_TAR(r3)
mtspr SPRN_TAR, r4
- mtspr SPRN_PPR, r5
- mtspr SPRN_DSCR, r6
- /* ******************** CR,LR,CCR,MSR ********** */
- ld r3, _CTR(r7)
- ld r4, _LINK(r7)
- ld r5, _CCR(r7)
- ld r6, _XER(r7)
-
- mtctr r3
- mtlr r4
- mtcr r5
- mtxer r6
+ /* Load up the PPR and DSCR in GPRs only at this stage */
+ ld r5, THREAD_TM_DSCR(r3)
+ ld r6, THREAD_TM_PPR(r3)
/* Clear the MSR RI since we are about to change R1. EE is already off
*/
@@ -384,19 +403,26 @@ restore_gprs:
mtmsrd r4, 1
REST_4GPRS(0, r7) /* GPR0-3 */
- REST_GPR(4, r7) /* GPR4-6 */
- REST_GPR(5, r7)
- REST_GPR(6, r7)
+ REST_GPR(4, r7) /* GPR4 */
REST_4GPRS(8, r7) /* GPR8-11 */
REST_2GPRS(12, r7) /* GPR12-13 */
REST_NVGPRS(r7) /* GPR14-31 */
- ld r7, GPR7(r7) /* GPR7 */
+ /* Load up PPR and DSCR here so we don't run with user values for long
+ */
+ mtspr SPRN_DSCR, r5
+ mtspr SPRN_PPR, r6
+
+ REST_GPR(5, r7) /* GPR5-7 */
+ REST_GPR(6, r7)
+ ld r7, GPR7(r7)
/* Commit register state as checkpointed state: */
TRECHKPT
+ HMT_MEDIUM
+
/* Our transactional state has now changed.
*
* Now just get out of here. Transactional (current) state will be
@@ -419,6 +445,12 @@ restore_gprs:
mtcr r4
mtlr r0
ld r2, 40(r1)
+
+ /* Load system default DSCR */
+ ld r4, DSCR_DEFAULT@toc(r2)
+ ld r0, 0(r4)
+ mtspr SPRN_DSCR, r0
+
blr
/* ****************************************************************** */
Patches currently in stable-queue which might be from mikey@xxxxxxxxxxx are
queue-3.11/powerpc-tm-switch-out-userspace-ppr-and-dscr-sooner.patch
queue-3.11/powerpc-tm-turn-interrupts-hard-off-in-tm_reclaim.patch
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