From f9d4861fc32b995b1616775614459b8f266c803c Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Fri, 20 Jan 2012 12:01:13 +0100 Subject: ARM: 7294/1: vectors: use gate_vma for vectors user mapping The current user mapping for the vectors page is inserted as a `horrible hack vma' into each task via arch_setup_additional_pages. This causes problems with the MM subsystem and vm_normal_page, as described here: https://lkml.org/lkml/2012/1/14/55 Following the suggestion from Hugh in the above thread, this patch uses the gate_vma for the vectors user mapping, therefore consolidating the horrible hack VMAs into one. Acked-and-Tested-by: Nicolas Pitre Signed-off-by: Will Deacon Signed-off-by: Russell King --- arch/arm/include/asm/mmu_context.h | 29 +---------------------------- 1 file changed, 1 insertion(+), 28 deletions(-) (limited to 'arch/arm/include/asm/mmu_context.h') diff --git a/arch/arm/include/asm/mmu_context.h b/arch/arm/include/asm/mmu_context.h index 71605d9f8e4..a0b3cac0547 100644 --- a/arch/arm/include/asm/mmu_context.h +++ b/arch/arm/include/asm/mmu_context.h @@ -18,6 +18,7 @@ #include #include #include +#include void __check_kvm_seq(struct mm_struct *mm); @@ -133,32 +134,4 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next, #define deactivate_mm(tsk,mm) do { } while (0) #define activate_mm(prev,next) switch_mm(prev, next, NULL) -/* - * We are inserting a "fake" vma for the user-accessible vector page so - * gdb and friends can get to it through ptrace and /proc//mem. - * But we also want to remove it before the generic code gets to see it - * during process exit or the unmapping of it would cause total havoc. - * (the macro is used as remove_vma() is static to mm/mmap.c) - */ -#define arch_exit_mmap(mm) \ -do { \ - struct vm_area_struct *high_vma = find_vma(mm, 0xffff0000); \ - if (high_vma) { \ - BUG_ON(high_vma->vm_next); /* it should be last */ \ - if (high_vma->vm_prev) \ - high_vma->vm_prev->vm_next = NULL; \ - else \ - mm->mmap = NULL; \ - rb_erase(&high_vma->vm_rb, &mm->mm_rb); \ - mm->mmap_cache = NULL; \ - mm->map_count--; \ - remove_vma(high_vma); \ - } \ -} while (0) - -static inline void arch_dup_mmap(struct mm_struct *oldmm, - struct mm_struct *mm) -{ -} - #endif -- cgit v1.2.3 From 7fec1b57b8a925d83c194f995f83d9f8442fd48e Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Mon, 28 Nov 2011 13:53:28 +0000 Subject: ARM: Remove __ARCH_WANT_INTERRUPTS_ON_CTXSW on ASID-capable CPUs Since the ASIDs must be unique to an mm across all the CPUs in a system, the __new_context() function needs to broadcast a context reset event to all the CPUs during ASID allocation if a roll-over occurred. Such IPIs cannot be issued with interrupts disabled and ARM had to define __ARCH_WANT_INTERRUPTS_ON_CTXSW. This patch changes the check_context() function to check_and_switch_context() called from switch_mm(). In case of ASID-capable CPUs (ARMv6 onwards), if a new ASID is needed and the interrupts are disabled, it defers the __new_context() and cpu_switch_mm() calls to the post-lock switch hook where the interrupts are enabled. Setting the reserved TTBR0 was also moved to check_and_switch_context() from cpu_v7_switch_mm(). Reviewed-by: Will Deacon Tested-by: Will Deacon Reviewed-by: Frank Rowand Tested-by: Marc Zyngier Signed-off-by: Catalin Marinas --- arch/arm/include/asm/mmu_context.h | 72 +++++++++++++++++++++++++++++--------- 1 file changed, 56 insertions(+), 16 deletions(-) (limited to 'arch/arm/include/asm/mmu_context.h') diff --git a/arch/arm/include/asm/mmu_context.h b/arch/arm/include/asm/mmu_context.h index a0b3cac0547..94e265cb514 100644 --- a/arch/arm/include/asm/mmu_context.h +++ b/arch/arm/include/asm/mmu_context.h @@ -49,39 +49,80 @@ DECLARE_PER_CPU(struct mm_struct *, current_mm); void __init_new_context(struct task_struct *tsk, struct mm_struct *mm); void __new_context(struct mm_struct *mm); +void cpu_set_reserved_ttbr0(void); -static inline void check_context(struct mm_struct *mm) +static inline void switch_new_context(struct mm_struct *mm) { - /* - * This code is executed with interrupts enabled. Therefore, - * mm->context.id cannot be updated to the latest ASID version - * on a different CPU (and condition below not triggered) - * without first getting an IPI to reset the context. The - * alternative is to take a read_lock on mm->context.id_lock - * (after changing its type to rwlock_t). - */ - if (unlikely((mm->context.id ^ cpu_last_asid) >> ASID_BITS)) - __new_context(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) +{ if (unlikely(mm->context.kvm_seq != init_mm.context.kvm_seq)) __check_kvm_seq(mm); + + /* + * 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) >> 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 (it sends IPIs). + */ + 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) -#else +#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)) + switch_new_context(current->mm); +} -static inline void check_context(struct mm_struct *mm) +#else /* !CONFIG_CPU_HAS_ASID */ + +static inline void check_and_switch_context(struct mm_struct *mm, + struct task_struct *tsk) { #ifdef CONFIG_MMU if (unlikely(mm->context.kvm_seq != init_mm.context.kvm_seq)) __check_kvm_seq(mm); + cpu_switch_mm(mm->pgd, mm); #endif } #define init_new_context(tsk,mm) 0 -#endif +#define finish_arch_post_lock_switch() do { } while (0) + +#endif /* CONFIG_CPU_HAS_ASID */ #define destroy_context(mm) do { } while(0) @@ -123,8 +164,7 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next, struct mm_struct **crt_mm = &per_cpu(current_mm, cpu); *crt_mm = next; #endif - check_context(next); - cpu_switch_mm(next->pgd, next); + check_and_switch_context(next, tsk); if (cache_is_vivt()) cpumask_clear_cpu(cpu, mm_cpumask(prev)); } -- cgit v1.2.3 From e323969ccda2d69f02e047c08b03faa09215c72a Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Mon, 28 Nov 2011 15:59:10 +0000 Subject: ARM: Remove current_mm per-cpu variable The current_mm variable was used to store the new mm between the switch_mm() and switch_to() calls where an IPI to reset the context could have set the wrong mm. Since the interrupts are disabled during context switch, there is no need for this variable, current->active_mm already points to the current mm when interrupts are re-enabled. Reviewed-by: Will Deacon Tested-by: Will Deacon Reviewed-by: Frank Rowand Tested-by: Marc Zyngier Signed-off-by: Catalin Marinas --- arch/arm/include/asm/mmu_context.h | 7 ------- 1 file changed, 7 deletions(-) (limited to 'arch/arm/include/asm/mmu_context.h') diff --git a/arch/arm/include/asm/mmu_context.h b/arch/arm/include/asm/mmu_context.h index 94e265cb514..8da4b9c042f 100644 --- a/arch/arm/include/asm/mmu_context.h +++ b/arch/arm/include/asm/mmu_context.h @@ -43,9 +43,6 @@ void __check_kvm_seq(struct mm_struct *mm); #define ASID_FIRST_VERSION (1 << ASID_BITS) extern unsigned int cpu_last_asid; -#ifdef CONFIG_SMP -DECLARE_PER_CPU(struct mm_struct *, current_mm); -#endif void __init_new_context(struct task_struct *tsk, struct mm_struct *mm); void __new_context(struct mm_struct *mm); @@ -160,10 +157,6 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next, __flush_icache_all(); #endif if (!cpumask_test_and_set_cpu(cpu, mm_cpumask(next)) || prev != next) { -#ifdef CONFIG_SMP - struct mm_struct **crt_mm = &per_cpu(current_mm, cpu); - *crt_mm = next; -#endif check_and_switch_context(next, tsk); if (cache_is_vivt()) cpumask_clear_cpu(cpu, mm_cpumask(prev)); -- cgit v1.2.3 From b9d4d42ad901cc848ac87f1cb8923fded3645568 Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Mon, 28 Nov 2011 21:57:24 +0000 Subject: ARM: Remove __ARCH_WANT_INTERRUPTS_ON_CTXSW on pre-ARMv6 CPUs This patch removes the __ARCH_WANT_INTERRUPTS_ON_CTXSW definition for ARMv5 and earlier processors. On such processors, the context switch requires a full cache flush. To avoid high interrupt latencies, this patch defers the mm switching to the post-lock switch hook if the interrupts are disabled. Reviewed-by: Will Deacon Tested-by: Will Deacon Reviewed-by: Frank Rowand Tested-by: Marc Zyngier Signed-off-by: Catalin Marinas --- arch/arm/include/asm/mmu_context.h | 31 ++++++++++++++++++++++++++----- 1 file changed, 26 insertions(+), 5 deletions(-) (limited to 'arch/arm/include/asm/mmu_context.h') diff --git a/arch/arm/include/asm/mmu_context.h b/arch/arm/include/asm/mmu_context.h index 8da4b9c042f..0306bc642c0 100644 --- a/arch/arm/include/asm/mmu_context.h +++ b/arch/arm/include/asm/mmu_context.h @@ -105,19 +105,40 @@ static inline void finish_arch_post_lock_switch(void) #else /* !CONFIG_CPU_HAS_ASID */ +#ifdef CONFIG_MMU + static inline void check_and_switch_context(struct mm_struct *mm, struct task_struct *tsk) { -#ifdef CONFIG_MMU if (unlikely(mm->context.kvm_seq != init_mm.context.kvm_seq)) __check_kvm_seq(mm); - cpu_switch_mm(mm->pgd, mm); -#endif + + if (irqs_disabled()) + /* + * cpu_switch_mm() needs to flush the VIVT caches. To avoid + * high interrupt latencies, defer the call and continue + * running with the old mm. Since we only support UP systems + * on non-ASID CPUs, the old mm will remain valid until the + * finish_arch_post_lock_switch() call. + */ + set_ti_thread_flag(task_thread_info(tsk), TIF_SWITCH_MM); + else + cpu_switch_mm(mm->pgd, mm); } -#define init_new_context(tsk,mm) 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; + cpu_switch_mm(mm->pgd, mm); + } +} -#define finish_arch_post_lock_switch() do { } while (0) +#endif /* CONFIG_MMU */ + +#define init_new_context(tsk,mm) 0 #endif /* CONFIG_CPU_HAS_ASID */ -- cgit v1.2.3