diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 47573f71b8..d909fec30d 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -1525,10 +1525,8 @@ int hvm_vcpu_initialise(struct vcpu *v)
     if ( (rc = hvm_funcs.vcpu_initialise(v)) != 0 ) /* teardown: hvm_funcs.vcpu_destroy */
         goto fail3;
 
-    softirq_tasklet_init(
-        &v->arch.hvm.assert_evtchn_irq_tasklet,
-        (void(*)(unsigned long))hvm_assert_evtchn_irq,
-        (unsigned long)v);
+    softirq_tasklet_init(&v->arch.hvm.assert_evtchn_irq_tasklet,
+                         (void (*)(void *))hvm_assert_evtchn_irq, v);
 
     v->arch.hvm.inject_event.vector = HVM_EVENT_VECTOR_UNSET;
 
diff --git a/xen/arch/x86/hvm/vlapic.c b/xen/arch/x86/hvm/vlapic.c
index 9b8afb72e8..06235f183e 100644
--- a/xen/arch/x86/hvm/vlapic.c
+++ b/xen/arch/x86/hvm/vlapic.c
@@ -309,9 +309,9 @@ static void vlapic_init_sipi_one(struct vcpu *target, uint32_t icr)
     vcpu_unpause(target);
 }
 
-static void vlapic_init_sipi_action(unsigned long _vcpu)
+static void vlapic_init_sipi_action(void *data)
 {
-    struct vcpu *origin = (struct vcpu *)_vcpu;
+    struct vcpu *origin = data;
     uint32_t icr = vcpu_vlapic(origin)->init_sipi.icr;
     uint32_t dest = vcpu_vlapic(origin)->init_sipi.dest;
     uint32_t short_hand = icr & APIC_SHORT_MASK;
@@ -1637,9 +1637,7 @@ int vlapic_init(struct vcpu *v)
 
     spin_lock_init(&vlapic->esr_lock);
 
-    tasklet_init(&vlapic->init_sipi.tasklet,
-                 vlapic_init_sipi_action,
-                 (unsigned long)v);
+    tasklet_init(&vlapic->init_sipi.tasklet, vlapic_init_sipi_action, v);
 
     if ( v->vcpu_id == 0 )
         register_mmio_handler(v->domain, &vlapic_mmio_ops);
diff --git a/xen/arch/x86/mm/shadow/common.c b/xen/arch/x86/mm/shadow/common.c
index 314d837602..6212ec2c4a 100644
--- a/xen/arch/x86/mm/shadow/common.c
+++ b/xen/arch/x86/mm/shadow/common.c
@@ -3471,9 +3471,9 @@ void shadow_audit_tables(struct vcpu *v)
 
 #ifdef CONFIG_PV
 
-void pv_l1tf_tasklet(unsigned long data)
+void pv_l1tf_tasklet(void *data)
 {
-    struct domain *d = (void *)data;
+    struct domain *d = data;
 
     domain_pause(d);
     paging_lock(d);
diff --git a/xen/common/domain.c b/xen/common/domain.c
index ccf689fcbe..865a1cb9d7 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -150,7 +150,7 @@ struct vcpu *vcpu_create(struct domain *d, unsigned int vcpu_id)
 
     spin_lock_init(&v->virq_lock);
 
-    tasklet_init(&v->continue_hypercall_tasklet, NULL, 0);
+    tasklet_init(&v->continue_hypercall_tasklet, NULL, NULL);
 
     grant_table_init_vcpu(v);
 
@@ -1661,9 +1661,9 @@ struct migrate_info {
 
 static DEFINE_PER_CPU(struct migrate_info *, continue_info);
 
-static void continue_hypercall_tasklet_handler(unsigned long _info)
+static void continue_hypercall_tasklet_handler(void *data)
 {
-    struct migrate_info *info = (struct migrate_info *)_info;
+    struct migrate_info *info = data;
     struct vcpu *v = info->vcpu;
     long res = -EINVAL;
 
@@ -1707,12 +1707,9 @@ int continue_hypercall_on_cpu(
         info->vcpu = curr;
         info->nest = 0;
 
-        tasklet_kill(
-            &curr->continue_hypercall_tasklet);
-        tasklet_init(
-            &curr->continue_hypercall_tasklet,
-            continue_hypercall_tasklet_handler,
-            (unsigned long)info);
+        tasklet_kill(&curr->continue_hypercall_tasklet);
+        tasklet_init(&curr->continue_hypercall_tasklet,
+                     continue_hypercall_tasklet_handler, info);
 
         get_knownalive_domain(curr->domain);
         vcpu_pause_nosync(curr);
diff --git a/xen/common/keyhandler.c b/xen/common/keyhandler.c
index dc6396b225..f50490d0f3 100644
--- a/xen/common/keyhandler.c
+++ b/xen/common/keyhandler.c
@@ -71,12 +71,12 @@ static struct keyhandler {
 #undef KEYHANDLER
 };
 
-static void keypress_action(unsigned long unused)
+static void keypress_action(void *unused)
 {
     handle_keypress(keypress_key, NULL);
 }
 
-static DECLARE_TASKLET(keypress_tasklet, keypress_action, 0);
+static DECLARE_TASKLET(keypress_tasklet, keypress_action, NULL);
 
 void handle_keypress(unsigned char key, struct cpu_user_regs *regs)
 {
@@ -199,11 +199,11 @@ static void dump_registers(unsigned char key, struct cpu_user_regs *regs)
     watchdog_enable();
 }
 
-static DECLARE_TASKLET(dump_hwdom_tasklet, NULL, 0);
+static DECLARE_TASKLET(dump_hwdom_tasklet, NULL, NULL);
 
-static void dump_hwdom_action(unsigned long arg)
+static void dump_hwdom_action(void *data)
 {
-    struct vcpu *v = (void *)arg;
+    struct vcpu *v = data;
 
     for ( ; ; )
     {
@@ -212,7 +212,7 @@ static void dump_hwdom_action(unsigned long arg)
             break;
         if ( softirq_pending(smp_processor_id()) )
         {
-            dump_hwdom_tasklet.data = (unsigned long)v;
+            dump_hwdom_tasklet.data = v;
             tasklet_schedule_on_cpu(&dump_hwdom_tasklet, v->processor);
             break;
         }
@@ -233,8 +233,7 @@ static void dump_hwdom_registers(unsigned char key)
         if ( alt_key_handling && softirq_pending(smp_processor_id()) )
         {
             tasklet_kill(&dump_hwdom_tasklet);
-            tasklet_init(&dump_hwdom_tasklet, dump_hwdom_action,
-                         (unsigned long)v);
+            tasklet_init(&dump_hwdom_tasklet, dump_hwdom_action, v);
             tasklet_schedule_on_cpu(&dump_hwdom_tasklet, v->processor);
             return;
         }
@@ -433,7 +432,7 @@ static void read_clocks(unsigned char key)
            maxdif_cycles, sumdif_cycles/count, count, dif_cycles);
 }
 
-static void run_all_nonirq_keyhandlers(unsigned long unused)
+static void run_all_nonirq_keyhandlers(void *unused)
 {
     /* Fire all the non-IRQ-context diagnostic keyhandlers */
     struct keyhandler *h;
@@ -455,7 +454,7 @@ static void run_all_nonirq_keyhandlers(unsigned long unused)
 }
 
 static DECLARE_TASKLET(run_all_keyhandlers_tasklet,
-                       run_all_nonirq_keyhandlers, 0);
+                       run_all_nonirq_keyhandlers, NULL);
 
 static void run_all_keyhandlers(unsigned char key, struct cpu_user_regs *regs)
 {
diff --git a/xen/common/stop_machine.c b/xen/common/stop_machine.c
index 681b40906d..33d9602217 100644
--- a/xen/common/stop_machine.c
+++ b/xen/common/stop_machine.c
@@ -134,8 +134,9 @@ int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu)
     return ret;
 }
 
-static void stopmachine_action(unsigned long cpu)
+static void stopmachine_action(void *data)
 {
+    unsigned int cpu = (unsigned long)data;
     enum stopmachine_state state = STOPMACHINE_START;
 
     BUG_ON(cpu != smp_processor_id());
@@ -181,7 +182,7 @@ static int cpu_callback(
 
     if ( action == CPU_UP_PREPARE )
         tasklet_init(&per_cpu(stopmachine_tasklet, cpu),
-                     stopmachine_action, cpu);
+                     stopmachine_action, hcpu);
 
     return NOTIFY_DONE;
 }
diff --git a/xen/common/tasklet.c b/xen/common/tasklet.c
index d4fea3151c..ac89511a09 100644
--- a/xen/common/tasklet.c
+++ b/xen/common/tasklet.c
@@ -199,8 +199,7 @@ static void migrate_tasklets_from_cpu(unsigned int cpu, struct list_head *list)
     spin_unlock_irqrestore(&tasklet_lock, flags);
 }
 
-void tasklet_init(
-    struct tasklet *t, void (*func)(unsigned long), unsigned long data)
+void tasklet_init(struct tasklet *t, void (*func)(void *), void *data)
 {
     memset(t, 0, sizeof(*t));
     INIT_LIST_HEAD(&t->list);
@@ -209,8 +208,7 @@ void tasklet_init(
     t->data = data;
 }
 
-void softirq_tasklet_init(
-    struct tasklet *t, void (*func)(unsigned long), unsigned long data)
+void softirq_tasklet_init(struct tasklet *t, void (*func)(void *), void *data)
 {
     tasklet_init(t, func, data);
     t->is_softirq = 1;
diff --git a/xen/common/trace.c b/xen/common/trace.c
index d1ef81407b..ebfc735b31 100644
--- a/xen/common/trace.c
+++ b/xen/common/trace.c
@@ -662,12 +662,12 @@ static inline void insert_lost_records(struct t_buf *buf)
  * Notification is performed in qtasklet to avoid deadlocks with contexts
  * which __trace_var() may be called from (e.g., scheduler critical regions).
  */
-static void trace_notify_dom0(unsigned long unused)
+static void trace_notify_dom0(void *unused)
 {
     send_global_virq(VIRQ_TBUF);
 }
 static DECLARE_SOFTIRQ_TASKLET(trace_notify_dom0_tasklet,
-                               trace_notify_dom0, 0);
+                               trace_notify_dom0, NULL);
 
 /**
  * __trace_var - Enters a trace tuple into the trace buffer for the current CPU.
diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index 844c5de74e..b31d789a5d 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -505,12 +505,12 @@ static void serial_rx(char c, struct cpu_user_regs *regs)
     __serial_rx(c, regs);
 }
 
-static void notify_dom0_con_ring(unsigned long unused)
+static void notify_dom0_con_ring(void *unused)
 {
     send_global_virq(VIRQ_CON_RING);
 }
 static DECLARE_SOFTIRQ_TASKLET(notify_dom0_con_ring_tasklet,
-                               notify_dom0_con_ring, 0);
+                               notify_dom0_con_ring, NULL);
 
 #ifdef CONFIG_X86
 static inline void xen_console_write_debug_port(const char *buf, size_t len)
diff --git a/xen/drivers/passthrough/amd/iommu_guest.c b/xen/drivers/passthrough/amd/iommu_guest.c
index 1f2bcfbe15..4ed6519e6e 100644
--- a/xen/drivers/passthrough/amd/iommu_guest.c
+++ b/xen/drivers/passthrough/amd/iommu_guest.c
@@ -435,11 +435,11 @@ static int do_invalidate_dte(struct domain *d, cmd_entry_t *cmd)
     return 0;
 }
 
-static void guest_iommu_process_command(unsigned long _d)
+static void guest_iommu_process_command(void *data)
 {
     unsigned long opcode, tail, head, entries_per_page, cmd_mfn;
     cmd_entry_t *cmd, *cmd_base;
-    struct domain *d = (struct domain *)_d;
+    struct domain *d = data;
     struct guest_iommu *iommu;
 
     iommu = domain_iommu(d);
@@ -837,8 +837,7 @@ int guest_iommu_init(struct domain* d)
     iommu->domain = d;
     hd->arch.g_iommu = iommu;
 
-    tasklet_init(&iommu->cmd_buffer_tasklet,
-                 guest_iommu_process_command, (unsigned long)d);
+    tasklet_init(&iommu->cmd_buffer_tasklet, guest_iommu_process_command, d);
 
     spin_lock_init(&iommu->lock);
 
diff --git a/xen/drivers/passthrough/amd/iommu_init.c b/xen/drivers/passthrough/amd/iommu_init.c
index 9509124158..2f26fed4a3 100644
--- a/xen/drivers/passthrough/amd/iommu_init.c
+++ b/xen/drivers/passthrough/amd/iommu_init.c
@@ -33,8 +33,8 @@
 static int __initdata nr_amd_iommus;
 static bool __initdata pci_init;
 
-static void do_amd_iommu_irq(unsigned long data);
-static DECLARE_SOFTIRQ_TASKLET(amd_iommu_irq_tasklet, do_amd_iommu_irq, 0);
+static void do_amd_iommu_irq(void *data);
+static DECLARE_SOFTIRQ_TASKLET(amd_iommu_irq_tasklet, do_amd_iommu_irq, NULL);
 
 unsigned int __read_mostly ivrs_bdf_entries;
 u8 __read_mostly ivhd_type;
@@ -723,7 +723,7 @@ static void iommu_check_ppr_log(struct amd_iommu *iommu)
     spin_unlock_irqrestore(&iommu->lock, flags);
 }
 
-static void do_amd_iommu_irq(unsigned long data)
+static void do_amd_iommu_irq(void *unused)
 {
     struct amd_iommu *iommu;
 
diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c
index 05e740757a..4e19cf56cc 100644
--- a/xen/drivers/passthrough/iommu.c
+++ b/xen/drivers/passthrough/iommu.c
@@ -369,7 +369,7 @@ int iommu_lookup_page(struct domain *d, dfn_t dfn, mfn_t *mfn,
     return iommu_call(hd->platform_ops, lookup_page, d, dfn, mfn, flags);
 }
 
-static void iommu_free_pagetables(unsigned long unused)
+static void iommu_free_pagetables(void *unused)
 {
     do {
         struct page_info *pg;
@@ -500,7 +500,7 @@ int __init iommu_setup(void)
                iommu_hwdom_passthrough ? "Passthrough" :
                iommu_hwdom_strict ? "Strict" : "Relaxed");
         printk("Interrupt remapping %sabled\n", iommu_intremap ? "en" : "dis");
-        tasklet_init(&iommu_pt_cleanup_tasklet, iommu_free_pagetables, 0);
+        tasklet_init(&iommu_pt_cleanup_tasklet, iommu_free_pagetables, NULL);
     }
 
     return rc;
diff --git a/xen/drivers/passthrough/vtd/iommu.c b/xen/drivers/passthrough/vtd/iommu.c
index 664556aa51..c56df8e58e 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -965,7 +965,7 @@ static void __do_iommu_page_fault(struct vtd_iommu *iommu)
     }
 }
 
-static void do_iommu_page_fault(unsigned long data)
+static void do_iommu_page_fault(void *unused)
 {
     struct acpi_drhd_unit *drhd;
 
@@ -2309,7 +2309,7 @@ static int __init vtd_setup(void)
         }
     }
 
-    softirq_tasklet_init(&vtd_fault_tasklet, do_iommu_page_fault, 0);
+    softirq_tasklet_init(&vtd_fault_tasklet, do_iommu_page_fault, NULL);
 
     if ( !iommu_qinval && iommu_intremap )
     {
diff --git a/xen/include/asm-x86/shadow.h b/xen/include/asm-x86/shadow.h
index 8ebb89c027..907c71f497 100644
--- a/xen/include/asm-x86/shadow.h
+++ b/xen/include/asm-x86/shadow.h
@@ -230,7 +230,7 @@ static inline bool pv_l1tf_check_l4e(struct domain *d, l4_pgentry_t l4e)
     return pv_l1tf_check_pte(d, 4, l4e.l4);
 }
 
-void pv_l1tf_tasklet(unsigned long data);
+void pv_l1tf_tasklet(void *data);
 
 static inline void pv_l1tf_domain_init(struct domain *d)
 {
@@ -238,8 +238,7 @@ static inline void pv_l1tf_domain_init(struct domain *d)
                                                   : opt_pv_l1tf_domu;
 
 #ifdef CONFIG_SHADOW_PAGING
-    tasklet_init(&d->arch.paging.shadow.pv_l1tf_tasklet,
-                 pv_l1tf_tasklet, (unsigned long)d);
+    tasklet_init(&d->arch.paging.shadow.pv_l1tf_tasklet, pv_l1tf_tasklet, d);
 #endif
 }
 
diff --git a/xen/include/xen/tasklet.h b/xen/include/xen/tasklet.h
index bc9ddace6d..ea73171f6e 100644
--- a/xen/include/xen/tasklet.h
+++ b/xen/include/xen/tasklet.h
@@ -21,8 +21,8 @@ struct tasklet
     bool_t is_softirq;
     bool_t is_running;
     bool_t is_dead;
-    void (*func)(unsigned long);
-    unsigned long data;
+    void (*func)(void *);
+    void *data;
 };
 
 #define _DECLARE_TASKLET(name, func, data, softirq)                     \
@@ -59,10 +59,8 @@ void tasklet_schedule_on_cpu(struct tasklet *t, unsigned int cpu);
 void tasklet_schedule(struct tasklet *t);
 void do_tasklet(void);
 void tasklet_kill(struct tasklet *t);
-void tasklet_init(
-    struct tasklet *t, void (*func)(unsigned long), unsigned long data);
-void softirq_tasklet_init(
-    struct tasklet *t, void (*func)(unsigned long), unsigned long data);
+void tasklet_init(struct tasklet *t, void (*func)(void *), void *data);
+void softirq_tasklet_init(struct tasklet *t, void (*func)(void *), void *data);
 void tasklet_subsys_init(void);
 
 #endif /* __XEN_TASKLET_H__ */
