iommu: remove unused iommu_ops method and tasklet

The VT-d and AMD IOMMU implementations both use the general x86 IOMMU page
table allocator and ARM always shares page tables with CPU. Hence there is no
need to retain the free_page_table() method or the tasklet which invokes it.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

xen/drivers/passthrough/iommu.c

@@ -49,10 +49,6 @@ bool_t __read_mostly amd_iommu_perdev_intremap = 1;
 
 DEFINE_PER_CPU(bool_t, iommu_dont_flush_iotlb);
 
-DEFINE_SPINLOCK(iommu_pt_cleanup_lock);
-PAGE_LIST_HEAD(iommu_pt_cleanup_list);
-static struct tasklet iommu_pt_cleanup_tasklet;
-
 static int __init parse_iommu_param(const char *s)
 {
     const char *ss;
@@ -226,9 +222,6 @@ static void iommu_teardown(struct domain *d)
     struct domain_iommu *hd = dom_iommu(d);
 
     iommu_vcall(hd->platform_ops, teardown, d);
-
-    if ( hd->platform_ops->free_page_table )
-        tasklet_schedule(&iommu_pt_cleanup_tasklet);
 }
 
 void iommu_domain_destroy(struct domain *d)
@@ -368,23 +361,6 @@ 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(void *unused)
-{
-    do {
-        struct page_info *pg;
-
-        spin_lock(&iommu_pt_cleanup_lock);
-        pg = page_list_remove_head(&iommu_pt_cleanup_list);
-        spin_unlock(&iommu_pt_cleanup_lock);
-        if ( !pg )
-            return;
-        iommu_vcall(iommu_get_ops(), free_page_table, pg);
-    } while ( !softirq_pending(smp_processor_id()) );
-
-    tasklet_schedule_on_cpu(&iommu_pt_cleanup_tasklet,
-                            cpumask_cycle(smp_processor_id(), &cpu_online_map));
-}
-
 int iommu_iotlb_flush(struct domain *d, dfn_t dfn, unsigned int page_count,
                       unsigned int flush_flags)
 {
@@ -508,7 +484,6 @@ int __init iommu_setup(void)
 #ifndef iommu_intremap
         printk("Interrupt remapping %sabled\n", iommu_intremap ? "en" : "dis");
 #endif
-        tasklet_init(&iommu_pt_cleanup_tasklet, iommu_free_pagetables, NULL);
     }
 
     return rc;

xen/include/xen/iommu.h

@@ -263,8 +263,6 @@ struct iommu_ops {
     int __must_check (*lookup_page)(struct domain *d, dfn_t dfn, mfn_t *mfn,
                                     unsigned int *flags);
 
-    void (*free_page_table)(struct page_info *);
-
 #ifdef CONFIG_X86
     int (*enable_x2apic)(void);
     void (*disable_x2apic)(void);