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From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	 npiggin@gmail.com, dja@axtens.net
Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH v3 09/15] powerpc/8xx: Use alternative scratch registers in DTLB miss handler
Date: Tue, 10 Sep 2019 09:16:28 +0000 (UTC)
Message-ID: <7d8bd54fcdd927cbe492a9178f7dc7ca136f9238.1568106758.git.christophe.leroy@c-s.fr> (raw)
In-Reply-To: <cover.1568106758.git.christophe.leroy@c-s.fr>

In preparation of handling CONFIG_VMAP_STACK, DTLB miss handler need
to use different scratch registers than other exception handlers in
order to not jeopardise exception entry on stack DTLB misses.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/kernel/head_8xx.S | 27 ++++++++++++++-------------
 arch/powerpc/perf/8xx-pmu.c    | 12 ++++++++----
 2 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 25e19af49705..3de9c5f1746c 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -193,8 +193,9 @@ SystemCall:
 0:	lwz	r10, (dtlb_miss_counter - PAGE_OFFSET)@l(0)
 	addi	r10, r10, 1
 	stw	r10, (dtlb_miss_counter - PAGE_OFFSET)@l(0)
-	mfspr	r10, SPRN_SPRG_SCRATCH0
-	mfspr	r11, SPRN_SPRG_SCRATCH1
+	mfspr	r10, SPRN_DAR
+	mtspr	SPRN_DAR, r11	/* Tag DAR */
+	mfspr	r11, SPRN_M_TW
 	rfi
 #endif
 
@@ -337,8 +338,8 @@ ITLBMissLinear:
 
 	. = 0x1200
 DataStoreTLBMiss:
-	mtspr	SPRN_SPRG_SCRATCH0, r10
-	mtspr	SPRN_SPRG_SCRATCH1, r11
+	mtspr	SPRN_DAR, r10
+	mtspr	SPRN_M_TW, r11
 	mfcr	r11
 
 	/* If we are faulting a kernel address, we have to use the
@@ -403,10 +404,10 @@ DataStoreTLBMiss:
 	mtspr	SPRN_MD_RPN, r10	/* Update TLB entry */
 
 	/* Restore registers */
-	mtspr	SPRN_DAR, r11	/* Tag DAR */
 
-0:	mfspr	r10, SPRN_SPRG_SCRATCH0
-	mfspr	r11, SPRN_SPRG_SCRATCH1
+0:	mfspr	r10, SPRN_DAR
+	mtspr	SPRN_DAR, r11	/* Tag DAR */
+	mfspr	r11, SPRN_M_TW
 	rfi
 	patch_site	0b, patch__dtlbmiss_exit_1
 
@@ -422,10 +423,10 @@ DTLBMissIMMR:
 	mtspr	SPRN_MD_RPN, r10	/* Update TLB entry */
 
 	li	r11, RPN_PATTERN
-	mtspr	SPRN_DAR, r11	/* Tag DAR */
 
-0:	mfspr	r10, SPRN_SPRG_SCRATCH0
-	mfspr	r11, SPRN_SPRG_SCRATCH1
+0:	mfspr	r10, SPRN_DAR
+	mtspr	SPRN_DAR, r11	/* Tag DAR */
+	mfspr	r11, SPRN_M_TW
 	rfi
 	patch_site	0b, patch__dtlbmiss_exit_2
 
@@ -459,10 +460,10 @@ DTLBMissLinear:
 	mtspr	SPRN_MD_RPN, r10	/* Update TLB entry */
 
 	li	r11, RPN_PATTERN
-	mtspr	SPRN_DAR, r11	/* Tag DAR */
 
-0:	mfspr	r10, SPRN_SPRG_SCRATCH0
-	mfspr	r11, SPRN_SPRG_SCRATCH1
+0:	mfspr	r10, SPRN_DAR
+	mtspr	SPRN_DAR, r11	/* Tag DAR */
+	mfspr	r11, SPRN_M_TW
 	rfi
 	patch_site	0b, patch__dtlbmiss_exit_3
 
diff --git a/arch/powerpc/perf/8xx-pmu.c b/arch/powerpc/perf/8xx-pmu.c
index 19124b0b171a..1ad03c55c88c 100644
--- a/arch/powerpc/perf/8xx-pmu.c
+++ b/arch/powerpc/perf/8xx-pmu.c
@@ -157,10 +157,6 @@ static void mpc8xx_pmu_read(struct perf_event *event)
 
 static void mpc8xx_pmu_del(struct perf_event *event, int flags)
 {
-	/* mfspr r10, SPRN_SPRG_SCRATCH0 */
-	unsigned int insn = PPC_INST_MFSPR | __PPC_RS(R10) |
-			    __PPC_SPR(SPRN_SPRG_SCRATCH0);
-
 	mpc8xx_pmu_read(event);
 
 	/* If it was the last user, stop counting to avoid useles overhead */
@@ -173,6 +169,10 @@ static void mpc8xx_pmu_del(struct perf_event *event, int flags)
 		break;
 	case PERF_8xx_ID_ITLB_LOAD_MISS:
 		if (atomic_dec_return(&itlb_miss_ref) == 0) {
+			/* mfspr r10, SPRN_SPRG_SCRATCH0 */
+			unsigned int insn = PPC_INST_MFSPR | __PPC_RS(R10) |
+					    __PPC_SPR(SPRN_SPRG_SCRATCH0);
+
 			patch_instruction_site(&patch__itlbmiss_exit_1, insn);
 #ifndef CONFIG_PIN_TLB_TEXT
 			patch_instruction_site(&patch__itlbmiss_exit_2, insn);
@@ -181,6 +181,10 @@ static void mpc8xx_pmu_del(struct perf_event *event, int flags)
 		break;
 	case PERF_8xx_ID_DTLB_LOAD_MISS:
 		if (atomic_dec_return(&dtlb_miss_ref) == 0) {
+			/* mfspr r10, SPRN_DAR */
+			unsigned int insn = PPC_INST_MFSPR | __PPC_RS(R10) |
+					    __PPC_SPR(SPRN_DAR);
+
 			patch_instruction_site(&patch__dtlbmiss_exit_1, insn);
 			patch_instruction_site(&patch__dtlbmiss_exit_2, insn);
 			patch_instruction_site(&patch__dtlbmiss_exit_3, insn);
-- 
2.13.3


  parent reply index

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-10  9:16 [PATCH v3 00/15] Enable CONFIG_VMAP_STACK on PPC32 Christophe Leroy
2019-09-10  9:16 ` [PATCH v3 01/15] powerpc/32: replace MTMSRD() by mtmsr Christophe Leroy
2019-09-10  9:16 ` [PATCH v3 02/15] powerpc/32: Add EXCEPTION_PROLOG_0 in head_32.h Christophe Leroy
2019-09-10  9:16 ` [PATCH v3 03/15] powerpc/32: save DEAR/DAR before calling handle_page_fault Christophe Leroy
2019-09-10  9:16 ` [PATCH v3 04/15] powerpc/32: move MSR_PR test into EXCEPTION_PROLOG_0 Christophe Leroy
2019-09-10  9:16 ` [PATCH v3 05/15] powerpc/32: add a macro to get and/or save DAR and DSISR on stack Christophe Leroy
2019-09-10  9:16 ` [PATCH v3 06/15] powerpc/32: prepare for CONFIG_VMAP_STACK Christophe Leroy
2019-10-17  7:36   ` Andrew Donnellan
2019-10-18  6:46     ` Christophe Leroy
2019-10-18  7:09       ` Andrew Donnellan
2019-09-10  9:16 ` [PATCH v3 07/15] powerpc: align stack to 2 * THREAD_SIZE with VMAP_STACK Christophe Leroy
2019-09-10  9:16 ` [PATCH v3 08/15] powerpc/32: Add early stack overflow detection with VMAP stack Christophe Leroy
2019-09-10  9:16 ` Christophe Leroy [this message]
2019-09-10  9:16 ` [PATCH v3 10/15] powerpc/8xx: drop exception entries for non-existing exceptions Christophe Leroy
2019-09-10  9:16 ` [PATCH v3 11/15] powerpc/8xx: move DataStoreTLBMiss perf handler Christophe Leroy
2019-09-10  9:16 ` [PATCH v3 12/15] powerpc/8xx: split breakpoint exception Christophe Leroy
2019-09-10  9:16 ` [PATCH v3 13/15] powerpc/8xx: Enable CONFIG_VMAP_STACK Christophe Leroy
2019-09-10  9:16 ` [PATCH v3 14/15] powerpc/32s: reorganise DSI handler Christophe Leroy
2019-09-10  9:16 ` [PATCH v3 15/15] powerpc/32s: Activate CONFIG_VMAP_STACK Christophe Leroy

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