arm64: Process management
The patch adds support for thread creation and context switching. The
context switching CPU specific code is introduced with the CPU support
patch (part of the arch/arm64/mm/proc.S file). AArch64 supports
ASID-tagged TLBs and the ASID can be either 8 or 16-bit wide (detectable
via the ID_AA64AFR0_EL1 register).
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
new file mode 100644
index 0000000..f68465d
--- /dev/null
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -0,0 +1,152 @@
+/*
+ * Based on arch/arm/include/asm/mmu_context.h
+ *
+ * Copyright (C) 1996 Russell King.
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __ASM_MMU_CONTEXT_H
+#define __ASM_MMU_CONTEXT_H
+
+#include <linux/compiler.h>
+#include <linux/sched.h>
+
+#include <asm/cacheflush.h>
+#include <asm/proc-fns.h>
+#include <asm-generic/mm_hooks.h>
+#include <asm/cputype.h>
+#include <asm/pgtable.h>
+
+#define MAX_ASID_BITS 16
+
+extern unsigned int cpu_last_asid;
+
+void __init_new_context(struct task_struct *tsk, struct mm_struct *mm);
+void __new_context(struct mm_struct *mm);
+
+/*
+ * Set TTBR0 to empty_zero_page. No translations will be possible via TTBR0.
+ */
+static inline void cpu_set_reserved_ttbr0(void)
+{
+ unsigned long ttbr = page_to_phys(empty_zero_page);
+
+ asm(
+ " msr ttbr0_el1, %0 // set TTBR0\n"
+ " isb"
+ :
+ : "r" (ttbr));
+}
+
+static inline void switch_new_context(struct mm_struct *mm)
+{
+ unsigned long flags;
+
+ __new_context(mm);
+
+ local_irq_save(flags);
+ cpu_switch_mm(mm->pgd, mm);
+ local_irq_restore(flags);
+}
+
+static inline void check_and_switch_context(struct mm_struct *mm,
+ struct task_struct *tsk)
+{
+ /*
+ * Required during context switch to avoid speculative page table
+ * walking with the wrong TTBR.
+ */
+ cpu_set_reserved_ttbr0();
+
+ if (!((mm->context.id ^ cpu_last_asid) >> MAX_ASID_BITS))
+ /*
+ * The ASID is from the current generation, just switch to the
+ * new pgd. This condition is only true for calls from
+ * context_switch() and interrupts are already disabled.
+ */
+ cpu_switch_mm(mm->pgd, mm);
+ else if (irqs_disabled())
+ /*
+ * Defer the new ASID allocation until after the context
+ * switch critical region since __new_context() cannot be
+ * called with interrupts disabled.
+ */
+ set_ti_thread_flag(task_thread_info(tsk), TIF_SWITCH_MM);
+ else
+ /*
+ * That is a direct call to switch_mm() or activate_mm() with
+ * interrupts enabled and a new context.
+ */
+ switch_new_context(mm);
+}
+
+#define init_new_context(tsk,mm) (__init_new_context(tsk,mm),0)
+#define destroy_context(mm) do { } while(0)
+
+#define finish_arch_post_lock_switch \
+ finish_arch_post_lock_switch
+static inline void finish_arch_post_lock_switch(void)
+{
+ if (test_and_clear_thread_flag(TIF_SWITCH_MM)) {
+ struct mm_struct *mm = current->mm;
+ unsigned long flags;
+
+ __new_context(mm);
+
+ local_irq_save(flags);
+ cpu_switch_mm(mm->pgd, mm);
+ local_irq_restore(flags);
+ }
+}
+
+/*
+ * This is called when "tsk" is about to enter lazy TLB mode.
+ *
+ * mm: describes the currently active mm context
+ * tsk: task which is entering lazy tlb
+ * cpu: cpu number which is entering lazy tlb
+ *
+ * tsk->mm will be NULL
+ */
+static inline void
+enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
+{
+}
+
+/*
+ * This is the actual mm switch as far as the scheduler
+ * is concerned. No registers are touched. We avoid
+ * calling the CPU specific function when the mm hasn't
+ * actually changed.
+ */
+static inline void
+switch_mm(struct mm_struct *prev, struct mm_struct *next,
+ struct task_struct *tsk)
+{
+ unsigned int cpu = smp_processor_id();
+
+#ifdef CONFIG_SMP
+ /* check for possible thread migration */
+ if (!cpumask_empty(mm_cpumask(next)) &&
+ !cpumask_test_cpu(cpu, mm_cpumask(next)))
+ __flush_icache_all();
+#endif
+ if (!cpumask_test_and_set_cpu(cpu, mm_cpumask(next)) || prev != next)
+ check_and_switch_context(next, tsk);
+}
+
+#define deactivate_mm(tsk,mm) do { } while (0)
+#define activate_mm(prev,next) switch_mm(prev, next, NULL)
+
+#endif