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Message-Id: <297f30d8ba75cb0e9ebe0a776d96c19750105570.1550745320.git.christophe.leroy@c-s.fr>
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References: <cover.1550745320.git.christophe.leroy@c-s.fr>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Subject: [PATCH v2 03/10] powerpc/6xx: Store PGDIR physical address in a SPRG
To:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Date:   Thu, 21 Feb 2019 10:37:55 +0000 (UTC)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Use SPRN_SPRG2 to store the current thread PGDIR and
avoid reading thread_struct.pgdir at every TLB miss.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/include/asm/reg.h      |  1 +
 arch/powerpc/kernel/cpu_setup_6xx.S |  4 ++++
 arch/powerpc/kernel/head_32.S       | 25 ++++++++++++-------------
 arch/powerpc/mm/hash_low_32.S       |  3 +--
 4 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 371ef6e8248e..1f79e1d8fb0b 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -1167,6 +1167,7 @@
 #ifdef CONFIG_PPC_BOOK3S_32
 #define SPRN_SPRG_SCRATCH0	SPRN_SPRG0
 #define SPRN_SPRG_SCRATCH1	SPRN_SPRG1
+#define SPRN_SPRG_PGDIR		SPRN_SPRG2
 #define SPRN_SPRG_603_LRU	SPRN_SPRG4
 #endif
 
diff --git a/arch/powerpc/kernel/cpu_setup_6xx.S b/arch/powerpc/kernel/cpu_setup_6xx.S
index 8c069e96c478..6f1c11e0691f 100644
--- a/arch/powerpc/kernel/cpu_setup_6xx.S
+++ b/arch/powerpc/kernel/cpu_setup_6xx.S
@@ -24,6 +24,10 @@ BEGIN_MMU_FTR_SECTION
 	li	r10,0
 	mtspr	SPRN_SPRG_603_LRU,r10		/* init SW LRU tracking */
 END_MMU_FTR_SECTION_IFSET(MMU_FTR_NEED_DTLB_SW_LRU)
+	lis	r10, (swapper_pg_dir - PAGE_OFFSET)@h
+	ori	r10, r10, (swapper_pg_dir - PAGE_OFFSET)@l
+	mtspr	SPRN_SPRG_PGDIR, r10
+
 BEGIN_FTR_SECTION
 	bl	__init_fpu_registers
 END_FTR_SECTION_IFCLR(CPU_FTR_FPU_UNAVAILABLE)
diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index 04128899a0a5..2b0a26f66115 100644
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -500,16 +500,15 @@ InstructionTLBMiss:
 	mfspr	r3,SPRN_IMISS
 	lis	r1,PAGE_OFFSET@h		/* check if kernel address */
 	cmplw	0,r1,r3
-	mfspr	r2,SPRN_SPRG_THREAD
+	mfspr	r2, SPRN_SPRG_PGDIR
 	li	r1,_PAGE_USER|_PAGE_PRESENT|_PAGE_EXEC /* low addresses tested as user */
-	lwz	r2,PGDIR(r2)
 	bge-	112f
 	mfspr	r2,SPRN_SRR1		/* and MSR_PR bit from SRR1 */
 	rlwimi	r1,r2,32-12,29,29	/* shift MSR_PR to _PAGE_USER posn */
 	lis	r2,swapper_pg_dir@ha	/* if kernel address, use */
 	addi	r2,r2,swapper_pg_dir@l	/* kernel page table */
-112:	tophys(r2,r2)
-	rlwimi	r2,r3,12,20,29		/* insert top 10 bits of address */
+	tophys(r2,r2)
+112:	rlwimi	r2,r3,12,20,29		/* insert top 10 bits of address */
 	lwz	r2,0(r2)		/* get pmd entry */
 	rlwinm.	r2,r2,0,0,19		/* extract address of pte page */
 	beq-	InstructionAddressInvalid	/* return if no mapping */
@@ -574,16 +573,15 @@ DataLoadTLBMiss:
 	mfspr	r3,SPRN_DMISS
 	lis	r1,PAGE_OFFSET@h		/* check if kernel address */
 	cmplw	0,r1,r3
-	mfspr	r2,SPRN_SPRG_THREAD
+	mfspr	r2, SPRN_SPRG_PGDIR
 	li	r1,_PAGE_USER|_PAGE_PRESENT /* low addresses tested as user */
-	lwz	r2,PGDIR(r2)
 	bge-	112f
 	mfspr	r2,SPRN_SRR1		/* and MSR_PR bit from SRR1 */
 	rlwimi	r1,r2,32-12,29,29	/* shift MSR_PR to _PAGE_USER posn */
 	lis	r2,swapper_pg_dir@ha	/* if kernel address, use */
 	addi	r2,r2,swapper_pg_dir@l	/* kernel page table */
-112:	tophys(r2,r2)
-	rlwimi	r2,r3,12,20,29		/* insert top 10 bits of address */
+	tophys(r2,r2)
+112:	rlwimi	r2,r3,12,20,29		/* insert top 10 bits of address */
 	lwz	r2,0(r2)		/* get pmd entry */
 	rlwinm.	r2,r2,0,0,19		/* extract address of pte page */
 	beq-	DataAddressInvalid	/* return if no mapping */
@@ -658,16 +656,15 @@ DataStoreTLBMiss:
 	mfspr	r3,SPRN_DMISS
 	lis	r1,PAGE_OFFSET@h		/* check if kernel address */
 	cmplw	0,r1,r3
-	mfspr	r2,SPRN_SPRG_THREAD
+	mfspr	r2, SPRN_SPRG_PGDIR
 	li	r1,_PAGE_RW|_PAGE_USER|_PAGE_PRESENT /* access flags */
-	lwz	r2,PGDIR(r2)
 	bge-	112f
 	mfspr	r2,SPRN_SRR1		/* and MSR_PR bit from SRR1 */
 	rlwimi	r1,r2,32-12,29,29	/* shift MSR_PR to _PAGE_USER posn */
 	lis	r2,swapper_pg_dir@ha	/* if kernel address, use */
 	addi	r2,r2,swapper_pg_dir@l	/* kernel page table */
-112:	tophys(r2,r2)
-	rlwimi	r2,r3,12,20,29		/* insert top 10 bits of address */
+	tophys(r2,r2)
+112:	rlwimi	r2,r3,12,20,29		/* insert top 10 bits of address */
 	lwz	r2,0(r2)		/* get pmd entry */
 	rlwinm.	r2,r2,0,0,19		/* extract address of pte page */
 	beq-	DataAddressInvalid	/* return if no mapping */
@@ -1024,14 +1021,16 @@ _ENTRY(switch_mmu_context)
 	li	r0,NUM_USER_SEGMENTS
 	mtctr	r0
 
+	lwz	r4, MM_PGD(r4)
 #ifdef CONFIG_BDI_SWITCH
 	/* Context switch the PTE pointer for the Abatron BDI2000.
 	 * The PGDIR is passed as second argument.
 	 */
-	lwz	r4,MM_PGD(r4)
 	lis	r5, abatron_pteptrs@ha
 	stw	r4, abatron_pteptrs@l + 0x4(r5)
 #endif
+	tophys(r4, r4)
+	mtspr	SPRN_SPRG_PGDIR, r4
 	li	r4,0
 	isync
 3:
diff --git a/arch/powerpc/mm/hash_low_32.S b/arch/powerpc/mm/hash_low_32.S
index 1e2df3e9f9ea..82e7dd0c0220 100644
--- a/arch/powerpc/mm/hash_low_32.S
+++ b/arch/powerpc/mm/hash_low_32.S
@@ -70,9 +70,8 @@ _GLOBAL(hash_page)
 	/* Get PTE (linux-style) and check access */
 	lis	r0,KERNELBASE@h		/* check if kernel address */
 	cmplw	0,r4,r0
-	mfspr	r8,SPRN_SPRG_THREAD	/* current task's THREAD (phys) */
 	ori	r3,r3,_PAGE_USER|_PAGE_PRESENT /* test low addresses as user */
-	lwz	r5,PGDIR(r8)		/* virt page-table root */
+	mfspr	r5, SPRN_SPRG_PGDIR	/* virt page-table root */
 	blt+	112f			/* assume user more likely */
 	lis	r5,swapper_pg_dir@ha	/* if kernel address, use */
 	addi	r5,r5,swapper_pg_dir@l	/* kernel page table */
-- 
2.13.3