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Commit e9bdc3d6 authored by Michael Neuling's avatar Michael Neuling Committed by Benjamin Herrenschmidt
Browse files

powerpc/tm: Switch out userspace PPR and DSCR sooner 



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: default avatarMichael Neuling <mikey@neuling.org>
Cc: <stable@vger.kernel.org> # 3.9+
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent c69e63b0

arch/powerpc/kernel/tm.S

+63 −31
Original line number Diff line number Diff line
@@ -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,
@@ -188,11 +193,18 @@ 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
@@ -204,15 +216,19 @@ 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 */
@@ -235,14 +251,12 @@ 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.
@@ -259,7 +273,7 @@ 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 */
@@ -275,6 +289,12 @@ 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
@@ -359,25 +379,24 @@ 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)



	mtspr	SPRN_TAR,	r4

	mtspr	SPRN_PPR,	r5

	mtspr	SPRN_DSCR,	r6

	mtctr	r4

	mtlr	r5

	mtcr	r6

	mtxer	r8



	/* ******************** CR,LR,CCR,MSR ********** */

	ld	r3, _CTR(r7)

	ld	r4, _LINK(r7)

	ld	r5, _CCR(r7)

	ld	r6, _XER(r7)

	/* ******************** TAR ******************** */

	ld	r4, THREAD_TM_TAR(r3)

	mtspr	SPRN_TAR,	r4



	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

	 */
@@ -385,19 +404,26 @@ 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
@@ -420,6 +446,12 @@ 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



	/* ****************************************************************** */