diff options
| author | Jean-Philippe Brucker <jean-philippe.brucker@arm.com> | 2016-06-17 17:33:00 (GMT) |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2016-06-21 19:10:18 (GMT) |
| commit | f7e0efc9b50266f5317b50732efff98d40fc879a (patch) | |
| tree | cdbf55c7e1202782c62e3377557564bb023499d8 /arch | |
| parent | 33688abb2802ff3a230bd2441f765477b94cc89e (diff) | |
| download | linux-f7e0efc9b50266f5317b50732efff98d40fc879a.tar.xz | |
arm64: update ASID limit
During a rollover, we mark the active ASID on each CPU as reserved, before
allocating a new ID for the task that caused the rollover. This means that
with N CPUs, we can only guarantee the new task to obtain a valid ASID if
we have at least N+1 ASIDs. Update this limit in the initcall check.
Note that this restriction was introduced by commit 8e648066 on the
arch/arm side, which disallow re-using the previously active ASID on the
local CPU, as it would introduce a TLB race.
In addition, we only dispose of NUM_USER_ASIDS-1, since ASID 0 is
reserved. Add this restriction as well.
Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm64/mm/context.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c index b7b3978..efcf1f7 100644 --- a/arch/arm64/mm/context.c +++ b/arch/arm64/mm/context.c @@ -179,7 +179,7 @@ static u64 new_context(struct mm_struct *mm, unsigned int cpu) &asid_generation); flush_context(cpu); - /* We have at least 1 ASID per CPU, so this will always succeed */ + /* We have more ASIDs than CPUs, so this will always succeed */ asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, 1); set_asid: @@ -227,8 +227,11 @@ switch_mm_fastpath: static int asids_init(void) { asid_bits = get_cpu_asid_bits(); - /* If we end up with more CPUs than ASIDs, expect things to crash */ - WARN_ON(NUM_USER_ASIDS < num_possible_cpus()); + /* + * Expect allocation after rollover to fail if we don't have at least + * one more ASID than CPUs. ASID #0 is reserved for init_mm. + */ + WARN_ON(NUM_USER_ASIDS - 1 <= num_possible_cpus()); atomic64_set(&asid_generation, ASID_FIRST_VERSION); asid_map = kzalloc(BITS_TO_LONGS(NUM_USER_ASIDS) * sizeof(*asid_map), GFP_KERNEL); |