ARC700 exception (and intr handling) didn't have auto stack switching
thus had to rely on stashing a reg temporarily (to free it up) at a
known place in memory, allowing to code up the low level stack switching.
This however was not re-entrant in SMP which thus had to repurpose the
per-cpu MMU SCRATCH DATA register otherwise used to "cache" the task pdg
pointer (vs. reading it from mm struct)
The newer HS cores do have auto-stack switching and thus even SMP builds
can use the MMU SCRATCH reg as originally intended.
This patch fixes the restriction to ARC700 SMP builds only
Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
---
arch/arc/include/asm/entry-compact.h | 4 ++--
arch/arc/include/asm/mmu.h | 4 ++++
arch/arc/include/asm/mmu_context.h | 2 +-
arch/arc/include/asm/pgtable.h | 2 +-
arch/arc/mm/tlb.c | 2 +-
arch/arc/mm/tlbex.S | 2 +-
6 files changed, 10 insertions(+), 6 deletions(-)
diff --git a/arch/arc/include/asm/entry-compact.h b/arch/arc/include/asm/entry-compact.h
index 66a292335ee6..c3aa775878dc 100644
--- a/arch/arc/include/asm/entry-compact.h
+++ b/arch/arc/include/asm/entry-compact.h
@@ -130,7 +130,7 @@
* to be saved again on kernel mode stack, as part of pt_regs.
*-------------------------------------------------------------*/
.macro PROLOG_FREEUP_REG reg, mem
-#ifdef CONFIG_SMP
+#ifndef ARC_USE_SCRATCH_REG
sr \reg, [ARC_REG_SCRATCH_DATA0]
#else
st \reg, [\mem]
@@ -138,7 +138,7 @@
.endm
.macro PROLOG_RESTORE_REG reg, mem
-#ifdef CONFIG_SMP
+#ifndef ARC_USE_SCRATCH_REG
lr \reg, [ARC_REG_SCRATCH_DATA0]
#else
ld \reg, [\mem]
diff --git a/arch/arc/include/asm/mmu.h b/arch/arc/include/asm/mmu.h
index 98cadf1a09ac..0abacb82a72b 100644
--- a/arch/arc/include/asm/mmu.h
+++ b/arch/arc/include/asm/mmu.h
@@ -40,6 +40,10 @@
#define ARC_REG_SCRATCH_DATA0 0x46c
#endif
+#if defined(CONFIG_ISA_ARCV2) || !defined(CONFIG_SMP)
+#define ARC_USE_SCRATCH_REG
+#endif
+
/* Bits in MMU PID register */
#define __TLB_ENABLE (1 << 31)
#define __PROG_ENABLE (1 << 30)
diff --git a/arch/arc/include/asm/mmu_context.h b/arch/arc/include/asm/mmu_context.h
index 035470816be5..3a5e6a5b9ed6 100644
--- a/arch/arc/include/asm/mmu_context.h
+++ b/arch/arc/include/asm/mmu_context.h
@@ -144,7 +144,7 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
*/
cpumask_set_cpu(cpu, mm_cpumask(next));
-#ifndef CONFIG_SMP
+#ifdef ARC_USE_SCRATCH_REG
/* PGD cached in MMU reg to avoid 3 mem lookups: task->mm->pgd */
write_aux_reg(ARC_REG_SCRATCH_DATA0, next->pgd);
#endif
diff --git a/arch/arc/include/asm/pgtable.h b/arch/arc/include/asm/pgtable.h
index 1d87c18a2976..210eb1df17df 100644
--- a/arch/arc/include/asm/pgtable.h
+++ b/arch/arc/include/asm/pgtable.h
@@ -351,7 +351,7 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
* Thus use this macro only when you are certain that "current" is current
* e.g. when dealing with signal frame setup code etc
*/
-#ifndef CONFIG_SMP
+#ifdef ARC_USE_SCRATCH_REG
#define pgd_offset_fast(mm, addr) \
({ \
pgd_t *pgd_base = (pgd_t *) read_aux_reg(ARC_REG_SCRATCH_DATA0); \
diff --git a/arch/arc/mm/tlb.c b/arch/arc/mm/tlb.c
index 10025e199353..417f05ac4397 100644
--- a/arch/arc/mm/tlb.c
+++ b/arch/arc/mm/tlb.c
@@ -868,7 +868,7 @@ void arc_mmu_init(void)
write_aux_reg(ARC_REG_PID, MMU_ENABLE);
/* In smp we use this reg for interrupt 1 scratch */
-#ifndef CONFIG_SMP
+#ifdef ARC_USE_SCRATCH_REG
/* swapper_pg_dir is the pgd for the kernel, used by vmalloc */
write_aux_reg(ARC_REG_SCRATCH_DATA0, swapper_pg_dir);
#endif
diff --git a/arch/arc/mm/tlbex.S b/arch/arc/mm/tlbex.S
index c55d95dd2f39..d6fbdeda400a 100644
--- a/arch/arc/mm/tlbex.S
+++ b/arch/arc/mm/tlbex.S
@@ -193,7 +193,7 @@ ex_saved_reg1:
lr r2, [efa]
-#ifndef CONFIG_SMP
+#ifdef ARC_USE_SCRATCH_REG
lr r1, [ARC_REG_SCRATCH_DATA0] ; current pgd
#else
GET_CURR_TASK_ON_CPU r1
--
2.20.1
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