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// SPDX-License-Identifier: GPL-2.0
/*
* Generic ASID allocator.
*
* Based on arch/arm/mm/context.c
*
* Copyright (C) 2002-2003 Deep Blue Solutions Ltd, all rights reserved.
* Copyright (C) 2012 ARM Ltd.
*/
#include <linux/slab.h>
#include <linux/mm_types.h>
#include <asm/asid.h>
#define reserved_asid(info, cpu) *per_cpu_ptr((info)->reserved, cpu)
#define ASID_MASK(info) (~GENMASK((info)->bits - 1, 0))
#define ASID_FIRST_VERSION(info) (1UL << ((info)->bits))
#define asid2idx(info, asid) (((asid) & ~ASID_MASK(info)) >> (info)->ctxt_shift)
#define idx2asid(info, idx) (((idx) << (info)->ctxt_shift) & ~ASID_MASK(info))
static void flush_context(struct asid_info *info)
{
int i;
u64 asid;
/* Update the list of reserved ASIDs and the ASID bitmap. */
bitmap_clear(info->map, 0, NUM_CTXT_ASIDS(info));
for_each_possible_cpu(i) {
asid = atomic64_xchg_relaxed(&active_asid(info, i), 0);
/*
* If this CPU has already been through a
* rollover, but hasn't run another task in
* the meantime, we must preserve its reserved
* ASID, as this is the only trace we have of
* the process it is still running.
*/
if (asid == 0)
asid = reserved_asid(info, i);
__set_bit(asid2idx(info, asid), info->map);
reserved_asid(info, i) = asid;
}
/*
* Queue a TLB invalidation for each CPU to perform on next
* context-switch
*/
cpumask_setall(&info->flush_pending);
}
static bool check_update_reserved_asid(struct asid_info *info, u64 asid,
u64 newasid)
{
int cpu;
bool hit = false;
/*
* Iterate over the set of reserved ASIDs looking for a match.
* If we find one, then we can update our mm to use newasid
* (i.e. the same ASID in the current generation) but we can't
* exit the loop early, since we need to ensure that all copies
* of the old ASID are updated to reflect the mm. Failure to do
* so could result in us missing the reserved ASID in a future
* generation.
*/
for_each_possible_cpu(cpu) {
if (reserved_asid(info, cpu) == asid) {
hit = true;
reserved_asid(info, cpu) = newasid;
}
}
return hit;
}
static u64 new_context(struct asid_info *info, atomic64_t *pasid,
struct mm_struct *mm)
{
static u32 cur_idx = 1;
u64 asid = atomic64_read(pasid);
u64 generation = atomic64_read(&info->generation);
if (asid != 0) {
u64 newasid = generation | (asid & ~ASID_MASK(info));
/*
* If our current ASID was active during a rollover, we
* can continue to use it and this was just a false alarm.
*/
if (check_update_reserved_asid(info, asid, newasid))
return newasid;
/*
* We had a valid ASID in a previous life, so try to re-use
* it if possible.
*/
if (!__test_and_set_bit(asid2idx(info, asid), info->map))
return newasid;
}
/*
* Allocate a free ASID. If we can't find one, take a note of the
* currently active ASIDs and mark the TLBs as requiring flushes. We
* always count from ASID #2 (index 1), as we use ASID #0 when setting
* a reserved TTBR0 for the init_mm and we allocate ASIDs in even/odd
* pairs.
*/
asid = find_next_zero_bit(info->map, NUM_CTXT_ASIDS(info), cur_idx);
if (asid != NUM_CTXT_ASIDS(info))
goto set_asid;
/* We're out of ASIDs, so increment the global generation count */
generation = atomic64_add_return_relaxed(ASID_FIRST_VERSION(info),
&info->generation);
flush_context(info);
/* We have more ASIDs than CPUs, so this will always succeed */
asid = find_next_zero_bit(info->map, NUM_CTXT_ASIDS(info), 1);
set_asid:
__set_bit(asid, info->map);
cur_idx = asid;
cpumask_clear(mm_cpumask(mm));
return idx2asid(info, asid) | generation;
}
/*
* Generate a new ASID for the context.
*
* @pasid: Pointer to the current ASID batch allocated. It will be updated
* with the new ASID batch.
* @cpu: current CPU ID. Must have been acquired through get_cpu()
*/
void asid_new_context(struct asid_info *info, atomic64_t *pasid,
unsigned int cpu, struct mm_struct *mm)
{
unsigned long flags;
u64 asid;
raw_spin_lock_irqsave(&info->lock, flags);
/* Check that our ASID belongs to the current generation. */
asid = atomic64_read(pasid);
if ((asid ^ atomic64_read(&info->generation)) >> info->bits) {
asid = new_context(info, pasid, mm);
atomic64_set(pasid, asid);
}
if (cpumask_test_and_clear_cpu(cpu, &info->flush_pending))
info->flush_cpu_ctxt_cb();
atomic64_set(&active_asid(info, cpu), asid);
cpumask_set_cpu(cpu, mm_cpumask(mm));
raw_spin_unlock_irqrestore(&info->lock, flags);
}
/*
* Initialize the ASID allocator
*
* @info: Pointer to the asid allocator structure
* @bits: Number of ASIDs available
* @asid_per_ctxt: Number of ASIDs to allocate per-context. ASIDs are
* allocated contiguously for a given context. This value should be a power of
* 2.
*/
int asid_allocator_init(struct asid_info *info,
u32 bits, unsigned int asid_per_ctxt,
void (*flush_cpu_ctxt_cb)(void))
{
info->bits = bits;
info->ctxt_shift = ilog2(asid_per_ctxt);
info->flush_cpu_ctxt_cb = flush_cpu_ctxt_cb;
/*
* Expect allocation after rollover to fail if we don't have at least
* one more ASID than CPUs. ASID #0 is always reserved.
*/
WARN_ON(NUM_CTXT_ASIDS(info) - 1 <= num_possible_cpus());
atomic64_set(&info->generation, ASID_FIRST_VERSION(info));
info->map = kcalloc(BITS_TO_LONGS(NUM_CTXT_ASIDS(info)),
sizeof(*info->map), GFP_KERNEL);
if (!info->map)
return -ENOMEM;
raw_spin_lock_init(&info->lock);
return 0;
}
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