[PATCH V4 13/14] powerpc/mm/hash64: Store task size in PACA

[Aneesh Kumar K.V]

We can optmize the slice page size array copy to paca by copying only the
range based on task size. This will require us to not look at page size
array beyond task size in PACA on slb fault. To enable that copy task size
to paca which will be used during slb fault.

We can take slb fault on an mm even before we set the task_size in
setup_new_exec. To make sure our paca have the details of default page
size, init the mm->task_size with max value early. Later we will adjust this
based on task personality.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/paca.h   | 4 +++-
 arch/powerpc/kernel/asm-offsets.c | 4 ++++
 arch/powerpc/kernel/paca.c        | 1 +
 arch/powerpc/mm/slb_low.S         | 8 +++++++-
 4 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
index f48c250339fd..25f4a1c14759 100644
--- a/arch/powerpc/include/asm/paca.h
+++ b/arch/powerpc/include/asm/paca.h
@@ -144,7 +144,9 @@ struct paca_struct {
 	u16 mm_ctx_sllp;
 #endif
 #endif
-
+#ifdef CONFIG_PPC_STD_MMU_64
+	u64 task_size;
+#endif
 	/*
 	 * then miscellaneous read-write fields
 	 */
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 4367e7df51a1..a60ef1d976ab 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -189,6 +189,10 @@ int main(void)
 #endif /* CONFIG_PPC_MM_SLICES */
 #endif
 
+#ifdef CONFIG_PPC_STD_MMU_64
+	DEFINE(PACATASKSIZE, offsetof(struct paca_struct, task_size));
+#endif
+
 #ifdef CONFIG_PPC_BOOK3E
 	OFFSET(PACAPGD, paca_struct, pgd);
 	OFFSET(PACA_KERNELPGD, paca_struct, kernel_pgd);
diff --git a/arch/powerpc/kernel/paca.c b/arch/powerpc/kernel/paca.c
index bffdbd6d6774..50b60e23d07f 100644
--- a/arch/powerpc/kernel/paca.c
+++ b/arch/powerpc/kernel/paca.c
@@ -254,6 +254,7 @@ void copy_mm_to_paca(struct mm_struct *mm)
 	get_paca()->mm_ctx_id = context->id;
 #ifdef CONFIG_PPC_MM_SLICES
 	VM_BUG_ON(!mm->task_size);
+	get_paca()->task_size = mm->task_size;
 	get_paca()->mm_ctx_low_slices_psize = context->low_slices_psize;
 	memcpy(&get_paca()->mm_ctx_high_slices_psize,
 	       &context->high_slices_psize, TASK_SLICE_ARRAY_SZ(mm));
diff --git a/arch/powerpc/mm/slb_low.S b/arch/powerpc/mm/slb_low.S
index 35e91e89640f..b09e7748856f 100644
--- a/arch/powerpc/mm/slb_low.S
+++ b/arch/powerpc/mm/slb_low.S
@@ -149,7 +149,13 @@ END_MMU_FTR_SECTION_IFCLR(MMU_FTR_1T_SEGMENT)
 	 * For userspace addresses, make sure this is region 0.
 	 */
 	cmpdi	r9, 0
-	bne	8f
+	bne-	8f
+        /*
+         * user space make sure we are within the allowed limit
+	 */
+	ld	r11,PACATASKSIZE(r13)
+	cmpld	r3,r11
+	bge-	8f
 
 	/* when using slices, we extract the psize off the slice bitmaps
 	 * and then we need to get the sllp encoding off the mmu_psize_defs
-- 
2.7.4