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Message-Id: <4c54997edd3548fa54717915e7c6ebaf60f208c0.1622712515.git.christophe.leroy@csgroup.eu>
From:   Christophe Leroy <christophe.leroy@csgroup.eu>
Subject: [PATCH v3 1/6] powerpc/nohash: Refactor update of BDI2000 pointers in
 switch_mmu_context()
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,  3 Jun 2021 09:29:02 +0000 (UTC)
Precedence: bulk

Instead of duplicating the update of BDI2000 pointers in
set_context(), do it directly from switch_mmu_context().

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
v3: Do it only for nohash platforms, book3s/32 will have its own as part of converting switch_mmu_context() to C.
---
 arch/powerpc/kernel/head_40x.S       | 14 --------------
 arch/powerpc/kernel/head_44x.S       | 16 ----------------
 arch/powerpc/kernel/head_8xx.S       |  7 -------
 arch/powerpc/kernel/head_book3s_32.S |  6 ------
 arch/powerpc/kernel/head_fsl_booke.S | 16 ----------------
 arch/powerpc/mm/nohash/8xx.c         |  6 ------
 arch/powerpc/mm/nohash/mmu_context.c |  8 ++++++++
 arch/powerpc/mm/nohash/tlb_low.S     |  8 --------
 8 files changed, 8 insertions(+), 73 deletions(-)

diff --git a/arch/powerpc/kernel/head_40x.S b/arch/powerpc/kernel/head_40x.S
index e1360b88b6cb..7ef1bbc23bed 100644
--- a/arch/powerpc/kernel/head_40x.S
+++ b/arch/powerpc/kernel/head_40x.S
@@ -703,14 +703,6 @@ _GLOBAL(abort)
         mtspr   SPRN_DBCR0,r13
 
 _GLOBAL(set_context)
-
-#ifdef CONFIG_BDI_SWITCH
-	/* Context switch the PTE pointer for the Abatron BDI2000.
-	 * The PGDIR is the second parameter.
-	 */
-	lis	r5, abatron_pteptrs@ha
-	stw	r4, abatron_pteptrs@l + 0x4(r5)
-#endif
 	sync
 	mtspr	SPRN_PID,r3
 	isync				/* Need an isync to flush shadow */
@@ -731,9 +723,3 @@ EXPORT_SYMBOL(empty_zero_page)
 	.globl	swapper_pg_dir
 swapper_pg_dir:
 	.space	PGD_TABLE_SIZE
-
-/* Room for two PTE pointers, usually the kernel and current user pointers
- * to their respective root page table.
- */
-abatron_pteptrs:
-	.space	8
diff --git a/arch/powerpc/kernel/head_44x.S b/arch/powerpc/kernel/head_44x.S
index 5c106ac36626..57509d90e409 100644
--- a/arch/powerpc/kernel/head_44x.S
+++ b/arch/powerpc/kernel/head_44x.S
@@ -781,15 +781,6 @@ _GLOBAL(__fixup_440A_mcheck)
 	blr
 
 _GLOBAL(set_context)
-
-#ifdef CONFIG_BDI_SWITCH
-	/* Context switch the PTE pointer for the Abatron BDI2000.
-	 * The PGDIR is the second parameter.
-	 */
-	lis	r5, abatron_pteptrs@h
-	ori	r5, r5, abatron_pteptrs@l
-	stw	r4, 0x4(r5)
-#endif
 	mtspr	SPRN_PID,r3
 	isync			/* Force context change */
 	blr
@@ -1259,13 +1250,6 @@ EXPORT_SYMBOL(empty_zero_page)
 swapper_pg_dir:
 	.space	PGD_TABLE_SIZE
 
-/*
- * Room for two PTE pointers, usually the kernel and current user pointers
- * to their respective root page table.
- */
-abatron_pteptrs:
-	.space	8
-
 #ifdef CONFIG_SMP
 	.align	12
 temp_boot_stack:
diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 7d445e4342c0..817df9fe7fb3 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -804,10 +804,3 @@ EXPORT_SYMBOL(empty_zero_page)
 	.globl	swapper_pg_dir
 swapper_pg_dir:
 	.space	PGD_TABLE_SIZE
-
-/* Room for two PTE table pointers, usually the kernel and current user
- * pointer to their respective root page table (pgdir).
- */
-	.globl	abatron_pteptrs
-abatron_pteptrs:
-	.space	8
diff --git a/arch/powerpc/kernel/head_book3s_32.S b/arch/powerpc/kernel/head_book3s_32.S
index 326262030279..32c27dac9b80 100644
--- a/arch/powerpc/kernel/head_book3s_32.S
+++ b/arch/powerpc/kernel/head_book3s_32.S
@@ -1282,9 +1282,3 @@ EXPORT_SYMBOL(empty_zero_page)
 	.globl	swapper_pg_dir
 swapper_pg_dir:
 	.space	PGD_TABLE_SIZE
-
-/* Room for two PTE pointers, usually the kernel and current user pointers
- * to their respective root page table.
- */
-abatron_pteptrs:
-	.space	8
diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/head_fsl_booke.S
index a1a5c3f10dc4..590f34cc5bb2 100644
--- a/arch/powerpc/kernel/head_fsl_booke.S
+++ b/arch/powerpc/kernel/head_fsl_booke.S
@@ -986,15 +986,6 @@ _GLOBAL(abort)
 	isync
 
 _GLOBAL(set_context)
-
-#ifdef CONFIG_BDI_SWITCH
-	/* Context switch the PTE pointer for the Abatron BDI2000.
-	 * The PGDIR is the second parameter.
-	 */
-	lis	r5, abatron_pteptrs@h
-	ori	r5, r5, abatron_pteptrs@l
-	stw	r4, 0x4(r5)
-#endif
 	mtspr	SPRN_PID,r3
 	isync			/* Force context change */
 	blr
@@ -1242,10 +1233,3 @@ EXPORT_SYMBOL(empty_zero_page)
 	.globl	swapper_pg_dir
 swapper_pg_dir:
 	.space	PGD_TABLE_SIZE
-
-/*
- * Room for two PTE pointers, usually the kernel and current user pointers
- * to their respective root page table.
- */
-abatron_pteptrs:
-	.space	8
diff --git a/arch/powerpc/mm/nohash/8xx.c b/arch/powerpc/mm/nohash/8xx.c
index 71bfdbedacee..f749acba5473 100644
--- a/arch/powerpc/mm/nohash/8xx.c
+++ b/arch/powerpc/mm/nohash/8xx.c
@@ -224,12 +224,6 @@ void set_context(unsigned long id, pgd_t *pgd)
 {
 	s16 offset = (s16)(__pa(swapper_pg_dir));
 
-	/* Context switch the PTE pointer for the Abatron BDI2000.
-	 * The PGDIR is passed as second argument.
-	 */
-	if (IS_ENABLED(CONFIG_BDI_SWITCH))
-		abatron_pteptrs[1] = pgd;
-
 	/* Register M_TWB will contain base address of level 1 table minus the
 	 * lower part of the kernel PGDIR base address, so that all accesses to
 	 * level 1 table are done relative to lower part of kernel PGDIR base
diff --git a/arch/powerpc/mm/nohash/mmu_context.c b/arch/powerpc/mm/nohash/mmu_context.c
index aac81c9f84a5..eae48635a9ac 100644
--- a/arch/powerpc/mm/nohash/mmu_context.c
+++ b/arch/powerpc/mm/nohash/mmu_context.c
@@ -50,6 +50,12 @@
 
 #include <mm/mmu_decl.h>
 
+/*
+ * Room for two PTE table pointers, usually the kernel and current user
+ * pointer to their respective root page table (pgdir).
+ */
+void *abatron_pteptrs[2];
+
 /*
  * The MPC8xx has only 16 contexts. We rotate through them on each task switch.
  * A better way would be to keep track of tasks that own contexts, and implement
@@ -357,6 +363,8 @@ void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next,
 
 	/* Flick the MMU and release lock */
 	pr_hardcont(" -> %d\n", id);
+	if (IS_ENABLED(CONFIG_BDI_SWITCH))
+		abatron_pteptrs[1] = next->pgd;
 	set_context(id, next->pgd);
 	raw_spin_unlock(&context_lock);
 }
diff --git a/arch/powerpc/mm/nohash/tlb_low.S b/arch/powerpc/mm/nohash/tlb_low.S
index 68797e072f55..b3d0f0127828 100644
--- a/arch/powerpc/mm/nohash/tlb_low.S
+++ b/arch/powerpc/mm/nohash/tlb_low.S
@@ -362,14 +362,6 @@ _GLOBAL(_tlbivax_bcast)
 	blr
 
 _GLOBAL(set_context)
-#ifdef CONFIG_BDI_SWITCH
-	/* Context switch the PTE pointer for the Abatron BDI2000.
-	 * The PGDIR is the second parameter.
-	 */
-	lis	r5, abatron_pteptrs@h
-	ori	r5, r5, abatron_pteptrs@l
-	stw	r4, 0x4(r5)
-#endif
 	mtspr	SPRN_PID,r3
 	isync			/* Force context change */
 	blr
-- 
2.25.0