Update Linux to v5.4.2
Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/mips/mm/context.c b/arch/mips/mm/context.c
new file mode 100644
index 0000000..b255640
--- /dev/null
+++ b/arch/mips/mm/context.c
@@ -0,0 +1,291 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/atomic.h>
+#include <linux/mmu_context.h>
+#include <linux/percpu.h>
+#include <linux/spinlock.h>
+
+static DEFINE_RAW_SPINLOCK(cpu_mmid_lock);
+
+static atomic64_t mmid_version;
+static unsigned int num_mmids;
+static unsigned long *mmid_map;
+
+static DEFINE_PER_CPU(u64, reserved_mmids);
+static cpumask_t tlb_flush_pending;
+
+static bool asid_versions_eq(int cpu, u64 a, u64 b)
+{
+ return ((a ^ b) & asid_version_mask(cpu)) == 0;
+}
+
+void get_new_mmu_context(struct mm_struct *mm)
+{
+ unsigned int cpu;
+ u64 asid;
+
+ /*
+ * This function is specific to ASIDs, and should not be called when
+ * MMIDs are in use.
+ */
+ if (WARN_ON(IS_ENABLED(CONFIG_DEBUG_VM) && cpu_has_mmid))
+ return;
+
+ cpu = smp_processor_id();
+ asid = asid_cache(cpu);
+
+ if (!((asid += cpu_asid_inc()) & cpu_asid_mask(&cpu_data[cpu]))) {
+ if (cpu_has_vtag_icache)
+ flush_icache_all();
+ local_flush_tlb_all(); /* start new asid cycle */
+ }
+
+ set_cpu_context(cpu, mm, asid);
+ asid_cache(cpu) = asid;
+}
+EXPORT_SYMBOL_GPL(get_new_mmu_context);
+
+void check_mmu_context(struct mm_struct *mm)
+{
+ unsigned int cpu = smp_processor_id();
+
+ /*
+ * This function is specific to ASIDs, and should not be called when
+ * MMIDs are in use.
+ */
+ if (WARN_ON(IS_ENABLED(CONFIG_DEBUG_VM) && cpu_has_mmid))
+ return;
+
+ /* Check if our ASID is of an older version and thus invalid */
+ if (!asid_versions_eq(cpu, cpu_context(cpu, mm), asid_cache(cpu)))
+ get_new_mmu_context(mm);
+}
+EXPORT_SYMBOL_GPL(check_mmu_context);
+
+static void flush_context(void)
+{
+ u64 mmid;
+ int cpu;
+
+ /* Update the list of reserved MMIDs and the MMID bitmap */
+ bitmap_clear(mmid_map, 0, num_mmids);
+
+ /* Reserve an MMID for kmap/wired entries */
+ __set_bit(MMID_KERNEL_WIRED, mmid_map);
+
+ for_each_possible_cpu(cpu) {
+ mmid = xchg_relaxed(&cpu_data[cpu].asid_cache, 0);
+
+ /*
+ * If this CPU has already been through a
+ * rollover, but hasn't run another task in
+ * the meantime, we must preserve its reserved
+ * MMID, as this is the only trace we have of
+ * the process it is still running.
+ */
+ if (mmid == 0)
+ mmid = per_cpu(reserved_mmids, cpu);
+
+ __set_bit(mmid & cpu_asid_mask(&cpu_data[cpu]), mmid_map);
+ per_cpu(reserved_mmids, cpu) = mmid;
+ }
+
+ /*
+ * Queue a TLB invalidation for each CPU to perform on next
+ * context-switch
+ */
+ cpumask_setall(&tlb_flush_pending);
+}
+
+static bool check_update_reserved_mmid(u64 mmid, u64 newmmid)
+{
+ bool hit;
+ int cpu;
+
+ /*
+ * Iterate over the set of reserved MMIDs looking for a match.
+ * If we find one, then we can update our mm to use newmmid
+ * (i.e. the same MMID in the current generation) but we can't
+ * exit the loop early, since we need to ensure that all copies
+ * of the old MMID are updated to reflect the mm. Failure to do
+ * so could result in us missing the reserved MMID in a future
+ * generation.
+ */
+ hit = false;
+ for_each_possible_cpu(cpu) {
+ if (per_cpu(reserved_mmids, cpu) == mmid) {
+ hit = true;
+ per_cpu(reserved_mmids, cpu) = newmmid;
+ }
+ }
+
+ return hit;
+}
+
+static u64 get_new_mmid(struct mm_struct *mm)
+{
+ static u32 cur_idx = MMID_KERNEL_WIRED + 1;
+ u64 mmid, version, mmid_mask;
+
+ mmid = cpu_context(0, mm);
+ version = atomic64_read(&mmid_version);
+ mmid_mask = cpu_asid_mask(&boot_cpu_data);
+
+ if (!asid_versions_eq(0, mmid, 0)) {
+ u64 newmmid = version | (mmid & mmid_mask);
+
+ /*
+ * If our current MMID was active during a rollover, we
+ * can continue to use it and this was just a false alarm.
+ */
+ if (check_update_reserved_mmid(mmid, newmmid)) {
+ mmid = newmmid;
+ goto set_context;
+ }
+
+ /*
+ * We had a valid MMID in a previous life, so try to re-use
+ * it if possible.
+ */
+ if (!__test_and_set_bit(mmid & mmid_mask, mmid_map)) {
+ mmid = newmmid;
+ goto set_context;
+ }
+ }
+
+ /* Allocate a free MMID */
+ mmid = find_next_zero_bit(mmid_map, num_mmids, cur_idx);
+ if (mmid != num_mmids)
+ goto reserve_mmid;
+
+ /* We're out of MMIDs, so increment the global version */
+ version = atomic64_add_return_relaxed(asid_first_version(0),
+ &mmid_version);
+
+ /* Note currently active MMIDs & mark TLBs as requiring flushes */
+ flush_context();
+
+ /* We have more MMIDs than CPUs, so this will always succeed */
+ mmid = find_first_zero_bit(mmid_map, num_mmids);
+
+reserve_mmid:
+ __set_bit(mmid, mmid_map);
+ cur_idx = mmid;
+ mmid |= version;
+set_context:
+ set_cpu_context(0, mm, mmid);
+ return mmid;
+}
+
+void check_switch_mmu_context(struct mm_struct *mm)
+{
+ unsigned int cpu = smp_processor_id();
+ u64 ctx, old_active_mmid;
+ unsigned long flags;
+
+ if (!cpu_has_mmid) {
+ check_mmu_context(mm);
+ write_c0_entryhi(cpu_asid(cpu, mm));
+ goto setup_pgd;
+ }
+
+ /*
+ * MMID switch fast-path, to avoid acquiring cpu_mmid_lock when it's
+ * unnecessary.
+ *
+ * The memory ordering here is subtle. If our active_mmids is non-zero
+ * and the MMID matches the current version, then we update the CPU's
+ * asid_cache with a relaxed cmpxchg. Racing with a concurrent rollover
+ * means that either:
+ *
+ * - We get a zero back from the cmpxchg and end up waiting on
+ * cpu_mmid_lock in check_mmu_context(). Taking the lock synchronises
+ * with the rollover and so we are forced to see the updated
+ * generation.
+ *
+ * - We get a valid MMID back from the cmpxchg, which means the
+ * relaxed xchg in flush_context will treat us as reserved
+ * because atomic RmWs are totally ordered for a given location.
+ */
+ ctx = cpu_context(cpu, mm);
+ old_active_mmid = READ_ONCE(cpu_data[cpu].asid_cache);
+ if (!old_active_mmid ||
+ !asid_versions_eq(cpu, ctx, atomic64_read(&mmid_version)) ||
+ !cmpxchg_relaxed(&cpu_data[cpu].asid_cache, old_active_mmid, ctx)) {
+ raw_spin_lock_irqsave(&cpu_mmid_lock, flags);
+
+ ctx = cpu_context(cpu, mm);
+ if (!asid_versions_eq(cpu, ctx, atomic64_read(&mmid_version)))
+ ctx = get_new_mmid(mm);
+
+ WRITE_ONCE(cpu_data[cpu].asid_cache, ctx);
+ raw_spin_unlock_irqrestore(&cpu_mmid_lock, flags);
+ }
+
+ /*
+ * Invalidate the local TLB if needed. Note that we must only clear our
+ * bit in tlb_flush_pending after this is complete, so that the
+ * cpu_has_shared_ftlb_entries case below isn't misled.
+ */
+ if (cpumask_test_cpu(cpu, &tlb_flush_pending)) {
+ if (cpu_has_vtag_icache)
+ flush_icache_all();
+ local_flush_tlb_all();
+ cpumask_clear_cpu(cpu, &tlb_flush_pending);
+ }
+
+ write_c0_memorymapid(ctx & cpu_asid_mask(&boot_cpu_data));
+
+ /*
+ * If this CPU shares FTLB entries with its siblings and one or more of
+ * those siblings hasn't yet invalidated its TLB following a version
+ * increase then we need to invalidate any TLB entries for our MMID
+ * that we might otherwise pick up from a sibling.
+ *
+ * We ifdef on CONFIG_SMP because cpu_sibling_map isn't defined in
+ * CONFIG_SMP=n kernels.
+ */
+#ifdef CONFIG_SMP
+ if (cpu_has_shared_ftlb_entries &&
+ cpumask_intersects(&tlb_flush_pending, &cpu_sibling_map[cpu])) {
+ /* Ensure we operate on the new MMID */
+ mtc0_tlbw_hazard();
+
+ /*
+ * Invalidate all TLB entries associated with the new
+ * MMID, and wait for the invalidation to complete.
+ */
+ ginvt_mmid();
+ sync_ginv();
+ }
+#endif
+
+setup_pgd:
+ TLBMISS_HANDLER_SETUP_PGD(mm->pgd);
+}
+EXPORT_SYMBOL_GPL(check_switch_mmu_context);
+
+static int mmid_init(void)
+{
+ if (!cpu_has_mmid)
+ return 0;
+
+ /*
+ * Expect allocation after rollover to fail if we don't have at least
+ * one more MMID than CPUs.
+ */
+ num_mmids = asid_first_version(0);
+ WARN_ON(num_mmids <= num_possible_cpus());
+
+ atomic64_set(&mmid_version, asid_first_version(0));
+ mmid_map = kcalloc(BITS_TO_LONGS(num_mmids), sizeof(*mmid_map),
+ GFP_KERNEL);
+ if (!mmid_map)
+ panic("Failed to allocate bitmap for %u MMIDs\n", num_mmids);
+
+ /* Reserve an MMID for kmap/wired entries */
+ __set_bit(MMID_KERNEL_WIRED, mmid_map);
+
+ pr_info("MMID allocator initialised with %u entries\n", num_mmids);
+ return 0;
+}
+early_initcall(mmid_init);