iova: Add CPU hotplug handler to flush rcaches

Like the Intel IOMMU driver already does, flush the per-IOVA domain
CPU rcache when a CPU goes offline - there's no point in keeping it.

Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/1616675401-151997-2-git-send-email-john.garry@huawei.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: John Garry

drivers/iommu/iova.c

@@ -25,6 +25,17 @@ static void init_iova_rcaches(struct iova_domain *iovad);
 static void free_iova_rcaches(struct iova_domain *iovad);
 static void fq_destroy_all_entries(struct iova_domain *iovad);
 static void fq_flush_timeout(struct timer_list *t);
+
+static int iova_cpuhp_dead(unsigned int cpu, struct hlist_node *node)
+{
+	struct iova_domain *iovad;
+
+	iovad = hlist_entry_safe(node, struct iova_domain, cpuhp_dead);
+
+	free_cpu_cached_iovas(cpu, iovad);
+	return 0;
+}
+
 static void free_global_cached_iovas(struct iova_domain *iovad);
 
 static struct iova *to_iova(struct rb_node *node)
@@ -56,6 +67,7 @@ init_iova_domain(struct iova_domain *iovad, unsigned long granule,
 	iovad->anchor.pfn_lo = iovad->anchor.pfn_hi = IOVA_ANCHOR;
 	rb_link_node(&iovad->anchor.node, NULL, &iovad->rbroot.rb_node);
 	rb_insert_color(&iovad->anchor.node, &iovad->rbroot);
+	cpuhp_state_add_instance_nocalls(CPUHP_IOMMU_IOVA_DEAD, &iovad->cpuhp_dead);
 	init_iova_rcaches(iovad);
 }
 EXPORT_SYMBOL_GPL(init_iova_domain);
@@ -299,10 +311,21 @@ int iova_cache_get(void)
 {
 	mutex_lock(&iova_cache_mutex);
 	if (!iova_cache_users) {
+		int ret;
+
+		ret = cpuhp_setup_state_multi(CPUHP_IOMMU_IOVA_DEAD, "iommu/iova:dead", NULL,
+					iova_cpuhp_dead);
+		if (ret) {
+			mutex_unlock(&iova_cache_mutex);
+			pr_err("Couldn't register cpuhp handler\n");
+			return ret;
+		}
+
 		iova_cache = kmem_cache_create(
 			"iommu_iova", sizeof(struct iova), 0,
 			SLAB_HWCACHE_ALIGN, NULL);
 		if (!iova_cache) {
+			cpuhp_remove_multi_state(CPUHP_IOMMU_IOVA_DEAD);
 			mutex_unlock(&iova_cache_mutex);
 			pr_err("Couldn't create iova cache\n");
 			return -ENOMEM;
@@ -324,8 +347,10 @@ void iova_cache_put(void)
 		return;
 	}
 	iova_cache_users--;
-	if (!iova_cache_users)
+	if (!iova_cache_users) {
+		cpuhp_remove_multi_state(CPUHP_IOMMU_IOVA_DEAD);
 		kmem_cache_destroy(iova_cache);
+	}
 	mutex_unlock(&iova_cache_mutex);
 }
 EXPORT_SYMBOL_GPL(iova_cache_put);
@@ -648,6 +673,9 @@ void put_iova_domain(struct iova_domain *iovad)
 {
 	struct iova *iova, *tmp;
 
+	cpuhp_state_remove_instance_nocalls(CPUHP_IOMMU_IOVA_DEAD,
+					    &iovad->cpuhp_dead);
+
 	free_iova_flush_queue(iovad);
 	free_iova_rcaches(iovad);
 	rbtree_postorder_for_each_entry_safe(iova, tmp, &iovad->rbroot, node)

include/linux/cpuhotplug.h

@@ -58,6 +58,7 @@ enum cpuhp_state {
 	CPUHP_NET_DEV_DEAD,
 	CPUHP_PCI_XGENE_DEAD,
 	CPUHP_IOMMU_INTEL_DEAD,
+	CPUHP_IOMMU_IOVA_DEAD,
 	CPUHP_LUSTRE_CFS_DEAD,
 	CPUHP_AP_ARM_CACHE_B15_RAC_DEAD,
 	CPUHP_PADATA_DEAD,

include/linux/iova.h

@@ -95,6 +95,7 @@ struct iova_domain {
 						   flush-queues */
 	atomic_t fq_timer_on;			/* 1 when timer is active, 0
 						   when not */
+	struct hlist_node	cpuhp_dead;
 };
 
 static inline unsigned long iova_size(struct iova *iova)