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Subject[PATCH RFC 12/14] arm64/lib: asid: Allow user to update the context under the lock
Date
Some users of the ASID allocator (e.g VMID) will require to update the
context when a new ASID is generated. This has to be protected by a lock
to prevent concurrent modification.

Rather than introducing yet another lock, it is possible to re-use the
allocator lock for that purpose. This patch introduces a new callback
that will be call when updating the context.

Signed-off-by: Julien Grall <julien.grall@arm.com>
---
arch/arm64/include/asm/asid.h | 12 ++++++++----
arch/arm64/lib/asid.c | 10 ++++++++--
arch/arm64/mm/context.c | 11 ++++++++---
3 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/include/asm/asid.h b/arch/arm64/include/asm/asid.h
index bb62b587f37f..d8d9dc875bec 100644
--- a/arch/arm64/include/asm/asid.h
+++ b/arch/arm64/include/asm/asid.h
@@ -23,6 +23,8 @@ struct asid_info
unsigned int ctxt_shift;
/* Callback to locally flush the context. */
void (*flush_cpu_ctxt_cb)(void);
+ /* Callback to call when a context is updated */
+ void (*update_ctxt_cb)(void *ctxt);
};

#define NUM_ASIDS(info) (1UL << ((info)->bits))
@@ -31,7 +33,7 @@ struct asid_info
#define active_asid(info, cpu) *per_cpu_ptr((info)->active, cpu)

void asid_new_context(struct asid_info *info, atomic64_t *pasid,
- unsigned int cpu);
+ unsigned int cpu, void *ctxt);

/*
* Check the ASID is still valid for the context. If not generate a new ASID.
@@ -40,7 +42,8 @@ void asid_new_context(struct asid_info *info, atomic64_t *pasid,
* @cpu: current CPU ID. Must have been acquired throught get_cpu()
*/
static inline void asid_check_context(struct asid_info *info,
- atomic64_t *pasid, unsigned int cpu)
+ atomic64_t *pasid, unsigned int cpu,
+ void *ctxt)
{
u64 asid, old_active_asid;

@@ -67,11 +70,12 @@ static inline void asid_check_context(struct asid_info *info,
old_active_asid, asid))
return;

- asid_new_context(info, pasid, cpu);
+ asid_new_context(info, pasid, cpu, ctxt);
}

int asid_allocator_init(struct asid_info *info,
u32 bits, unsigned int asid_per_ctxt,
- void (*flush_cpu_ctxt_cb)(void));
+ void (*flush_cpu_ctxt_cb)(void),
+ void (*update_ctxt_cb)(void *ctxt));

#endif
diff --git a/arch/arm64/lib/asid.c b/arch/arm64/lib/asid.c
index 72b71bfb32be..b47e6769c1bc 100644
--- a/arch/arm64/lib/asid.c
+++ b/arch/arm64/lib/asid.c
@@ -130,9 +130,10 @@ static u64 new_context(struct asid_info *info, atomic64_t *pasid)
* @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()
+ * @ctxt: Context to update when calling update_context
*/
void asid_new_context(struct asid_info *info, atomic64_t *pasid,
- unsigned int cpu)
+ unsigned int cpu, void *ctxt)
{
unsigned long flags;
u64 asid;
@@ -149,6 +150,9 @@ void asid_new_context(struct asid_info *info, atomic64_t *pasid,
info->flush_cpu_ctxt_cb();

atomic64_set(&active_asid(info, cpu), asid);
+
+ info->update_ctxt_cb(ctxt);
+
raw_spin_unlock_irqrestore(&info->lock, flags);
}

@@ -163,11 +167,13 @@ void asid_new_context(struct asid_info *info, atomic64_t *pasid,
*/
int asid_allocator_init(struct asid_info *info,
u32 bits, unsigned int asid_per_ctxt,
- void (*flush_cpu_ctxt_cb)(void))
+ void (*flush_cpu_ctxt_cb)(void),
+ void (*update_ctxt_cb)(void *ctxt))
{
info->bits = bits;
info->ctxt_shift = ilog2(asid_per_ctxt);
info->flush_cpu_ctxt_cb = flush_cpu_ctxt_cb;
+ info->update_ctxt_cb = update_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.
diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c
index 95ee7711a2ef..737b4bd7bbe7 100644
--- a/arch/arm64/mm/context.c
+++ b/arch/arm64/mm/context.c
@@ -82,7 +82,7 @@ void check_and_switch_context(struct mm_struct *mm, unsigned int cpu)
if (system_supports_cnp())
cpu_set_reserved_ttbr0();

- asid_check_context(&asid_info, &mm->context.id, cpu);
+ asid_check_context(&asid_info, &mm->context.id, cpu, mm);

arm64_apply_bp_hardening();

@@ -108,12 +108,17 @@ static void asid_flush_cpu_ctxt(void)
local_flush_tlb_all();
}

+static void asid_update_ctxt(void *ctxt)
+{
+ /* Nothing to do */
+}
+
static int asids_init(void)
{
u32 bits = get_cpu_asid_bits();

- if (!asid_allocator_init(&asid_info, bits, ASID_PER_CONTEXT,
- asid_flush_cpu_ctxt))
+ if (asid_allocator_init(&asid_info, bits, ASID_PER_CONTEXT,
+ asid_flush_cpu_ctxt, asid_update_ctxt))
panic("Unable to initialize ASID allocator for %lu ASIDs\n",
NUM_ASIDS(&asid_info));

--
2.11.0
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