diff options
| author | Catalin Marinas <catalin.marinas@arm.com> | 2007-02-05 14:47:40 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2007-02-08 14:49:24 +0000 |
| commit | 9d99df4b10eef130dacb5f772cd589c625b03634 (patch) | |
| tree | bf1cea618ef9380cdce9cfea8897da9fb961787b /arch/arm | |
| parent | 620879c9e33262426db0ade650be5d7a2046377b (diff) | |
[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 <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm')
| -rw-r--r-- | arch/arm/mm/context.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/arch/arm/mm/context.c b/arch/arm/mm/context.c index 79e80020242..9da43a0fdcd 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; } |