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arm64: mm: Add asid_gen_match() helper 

Add a macro to check if an ASID is from the current generation, since a
subsequent patch will introduce a third user for this test.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Link: https://lore.kernel.org/r/20200519175502.2504091-6-jean-philippe@linaro.org
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Jean-Philippe Brucker 2020-05-19 19:54:43 +02:00 committed by Will Deacon
parent bd4298c72b
commit 4fc92254bf
1 changed files with 5 additions and 3 deletions
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8
arch/arm64/mm/context.c
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@ -92,6 +92,9 @@ static void set_reserved_asid_bits(void)
bitmap_clear(asid_map, 0, NUM_USER_ASIDS);
}
#define asid_gen_match(asid) \
(!(((asid) ^ atomic64_read(&asid_generation)) >> asid_bits))
static void flush_context(void)
{
int i;
@ -220,8 +223,7 @@ void check_and_switch_context(struct mm_struct *mm, unsigned int cpu)
* because atomic RmWs are totally ordered for a given location.
*/
old_active_asid = atomic64_read(&per_cpu(active_asids, cpu));
if (old_active_asid &&
!((asid ^ atomic64_read(&asid_generation)) >> asid_bits) &&
if (old_active_asid && asid_gen_match(asid) &&
atomic64_cmpxchg_relaxed(&per_cpu(active_asids, cpu),
old_active_asid, asid))
goto switch_mm_fastpath;
@ -229,7 +231,7 @@ void check_and_switch_context(struct mm_struct *mm, unsigned int cpu)
raw_spin_lock_irqsave(&cpu_asid_lock, flags);
/* Check that our ASID belongs to the current generation. */
asid = atomic64_read(&mm->context.id);
if ((asid ^ atomic64_read(&asid_generation)) >> asid_bits) {
if (!asid_gen_match(asid)) {
asid = new_context(mm);
atomic64_set(&mm->context.id, asid);
}