Commit 9d99df4b authored by Catalin Marinas's avatar Catalin Marinas Committed by Russell King

[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: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 620879c9
......@@ -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;
}
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