[ 09/60] powerpc/tm: Fix context switching TAR, PPR and DSCR SPRs

Greg Kroah-Hartman
2013-08-13T06:48:05Z

From: Michael Neuling <mikey@neuling.org>

commit 28e61cc466d8daace4b0f04ba2b83e0bd68f5832 upstream.

If a transaction is rolled back, the Target Address Register (TAR), Processor
Priority Register (PPR) and Data Stream Control Register (DSCR) should be
restored to the checkpointed values before the transaction began. Any changes
to these SPRs inside the transaction should not be visible in the abort
handler.

Currently Linux doesn't save or restore the checkpointed TAR, PPR or DSCR. If
we preempt a processes inside a transaction which has modified any of these, on
process restore, that same transaction may be aborted we but we won't see the
checkpointed versions of these SPRs.

This adds checkpointed versions of these SPRs to the thread_struct and adds the
save/restore of these three SPRs to the treclaim/trechkpt code.

Without this if any of these SPRs are modified during a transaction, users may
incorrectly see a speculated SPR value even if the transaction is aborted.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/powerpc/include/asm/processor.h | 4 ++++
arch/powerpc/kernel/asm-offsets.c | 3 +++
arch/powerpc/kernel/tm.S | 20 ++++++++++++++++++++
3 files changed, 27 insertions(+)

--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -247,6 +247,10 @@ struct thread_struct {
unsigned long tm_orig_msr; /* Thread's MSR on ctx switch */
struct pt_regs ckpt_regs; /* Checkpointed registers */

+ unsigned long tm_tar;
+ unsigned long tm_ppr;
+ unsigned long tm_dscr;
+
/*
* Transactional FP and VSX 0-31 register set.
* NOTE: the sense of these is the opposite of the integer ckpt_regs!
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -139,6 +139,9 @@ int main(void)
DEFINE(THREAD_TM_TFHAR, offsetof(struct thread_struct, tm_tfhar));
DEFINE(THREAD_TM_TEXASR, offsetof(struct thread_struct, tm_texasr));
DEFINE(THREAD_TM_TFIAR, offsetof(struct thread_struct, tm_tfiar));
+ DEFINE(THREAD_TM_TAR, offsetof(struct thread_struct, tm_tar));
+ DEFINE(THREAD_TM_PPR, offsetof(struct thread_struct, tm_ppr));
+ DEFINE(THREAD_TM_DSCR, offsetof(struct thread_struct, tm_dscr));
DEFINE(PT_CKPT_REGS, offsetof(struct thread_struct, ckpt_regs));
DEFINE(THREAD_TRANSACT_VR0, offsetof(struct thread_struct,
transact_vr[0]));
--- a/arch/powerpc/kernel/tm.S
+++ b/arch/powerpc/kernel/tm.S
@@ -224,6 +224,16 @@ dont_backup_fp:
std r5, _CCR(r7)
std r6, _XER(r7)

+
+ /* ******************** TAR, PPR, DSCR ********** */
+ mfspr r3, SPRN_TAR
+ mfspr r4, SPRN_PPR
+ mfspr r5, SPRN_DSCR
+
+ std r3, THREAD_TM_TAR(r12)
+ std r4, THREAD_TM_PPR(r12)
+ std r5, THREAD_TM_DSCR(r12)
+
/* MSR and flags: We don't change CRs, and we don't need to alter
* MSR.
*/
@@ -338,6 +348,16 @@ dont_restore_fp:
mtmsr r6 /* FP/Vec off again! */

restore_gprs:
+
+ /* ******************** TAR, PPR, DSCR ********** */
+ ld r4, THREAD_TM_TAR(r3)
+ ld r5, THREAD_TM_PPR(r3)
+ ld r6, THREAD_TM_DSCR(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)