From 9d99df4b10eef130dacb5f772cd589c625b03634 Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Mon, 5 Feb 2007 14:47:40 +0100 Subject: [PATCH] [ARM] 4128/1: Architecture compliant TTBR changing sequence On newer architectures (ARMv6, ARMv7), the depth of the prefetch and branch prediction is implementation defined and there is a small risk of wrong ASID tagging when changing TTBR0 before setting the new context id. The recommended solution is to set a reserved ASID during TTBR changing. This patch reserves ASID 0. Signed-off-by: Catalin Marinas Signed-off-by: Russell King --- arch/arm/mm/context.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/arch/arm/mm/context.c b/arch/arm/mm/context.c index 79e800202424..9da43a0fdcdf 100644 --- a/arch/arm/mm/context.c +++ b/arch/arm/mm/context.c @@ -19,7 +19,8 @@ unsigned int cpu_last_asid = { 1 << ASID_BITS }; /* * We fork()ed a process, and we need a new context for the child * to run in. We reserve version 0 for initial tasks so we will - * always allocate an ASID. + * always allocate an ASID. The ASID 0 is reserved for the TTBR + * register changing sequence. */ void __init_new_context(struct task_struct *tsk, struct mm_struct *mm) { @@ -38,8 +39,15 @@ void __new_context(struct mm_struct *mm) * If we've used up all our ASIDs, we need * to start a new version and flush the TLB. */ - if ((asid & ~ASID_MASK) == 0) + if ((asid & ~ASID_MASK) == 0) { + asid = ++cpu_last_asid; + /* set the reserved ASID before flushing the TLB */ + asm("mcr p15, 0, %0, c13, c0, 1 @ set reserved context ID\n" + : + : "r" (0)); + isb(); flush_tlb_all(); + } mm->context.id = asid; } -- 2.39.5