vfn/support: introduce rwlock and convert mutex to rwlock for IOMMU look-up

include/vfn/support.h

@@ -42,6 +42,7 @@ extern "C" {
 #include <vfn/support/mem.h>
 #include <vfn/support/mmio.h>
 #include <vfn/support/mutex.h>
+#include <vfn/support/rwlock.h>
 #include <vfn/support/timer.h>
 #include <vfn/support/ticks.h>
 

include/vfn/support/meson.build

@@ -10,6 +10,7 @@ vfn_support_headers = files([
   'mem.h',
   'mmio.h',
   'mutex.h',
+  'rwlock.h',
   'ticks.h',
   'timer.h',
 ])

include/vfn/support/rwlock.h

@@ -0,0 +1,65 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later or MIT */
+
+/*
+ * This file is part of libvfn.
+ *
+ * Copyright (C) 2022 The libvfn Authors. All Rights Reserved.
+ *
+ * This library (libvfn) is dual licensed under the GNU Lesser General
+ * Public License version 2.1 or later or the MIT license. See the
+ * COPYING and LICENSE files for more information.
+ */
+
+#ifndef LIBVFN_SUPPORT_RWLOCK_H
+#define LIBVFN_SUPPORT_RWLOCK_H
+
+/*
+ * DOC: Autolockable read-write lock
+ *
+ * Define a __autolock() macro that will lock the given rwlock as well as ensure
+ * that it is unlocked when going out of scope. This is inspired by the
+ * polymorphic locking functions in QEMU (include/qemu/lockable.h), but this
+ * version only supports the pthread_rwlock_t.
+ */
+
+static inline pthread_rwlock_t *__rwlock_auto_rdlock(pthread_rwlock_t *rwlock)
+{
+	pthread_rwlock_rdlock(rwlock);
+	return rwlock;
+}
+
+static inline pthread_rwlock_t *__rwlock_auto_wrlock(pthread_rwlock_t *rwlock)
+{
+	pthread_rwlock_wrlock(rwlock);
+	return rwlock;
+}
+
+static inline void __rwlock_auto_unlock(pthread_rwlock_t *rwlock)
+{
+	if (rwlock)
+		pthread_rwlock_unlock(rwlock);
+}
+
+DEFINE_AUTOPTR(pthread_rwlock_t, __rwlock_auto_unlock)
+
+/**
+ * __autordlock - autolock rdlock
+ * @x: pointer to pthread rdlock
+ *
+ * Lock the rdlock and unlock it automatically when going out of scope.
+ */
+#define __autordlock(x) \
+	__autoptr(pthread_rwlock_t) \
+	glue(autordlock, __COUNTER__) __attribute__((__unused__)) = __rwlock_auto_rdlock(x)
+
+/**
+ * __autowrlock - autolock wrlock
+ * @x: pointer to pthread wrlock
+ *
+ * Lock the wrlock and unlock it automatically when going out of scope.
+ */
+#define __autowrlock(x) \
+	__autoptr(pthread_rwlock_t) \
+	glue(autowrlock, __COUNTER__) __attribute__((__unused__)) = __rwlock_auto_wrlock(x)
+
+#endif /* LIBVFN_SUPPORT_RWLOCK_H */

src/iommu/context.c

@@ -81,8 +81,6 @@ void iommu_ctx_init(struct iommu_ctx *ctx)
 	ctx->iova_ranges[0].start = IOVA_MIN;
 	ctx->iova_ranges[0].last = IOVA_MAX_39BITS - 1;
 
-	pthread_mutex_init(&ctx->lock, NULL);
-
 	skiplist_init(&ctx->map.list);
-	pthread_mutex_init(&ctx->map.lock, NULL);
+	pthread_rwlock_init(&ctx->map.lock, NULL);
 }

src/iommu/context.h

@@ -40,15 +40,14 @@ struct iova_mapping {
 };
 
 struct iova_map {
-	pthread_mutex_t lock;
+	pthread_rwlock_t lock;
 	struct skiplist list;
 };
 
 struct iommu_ctx {
 	struct iova_map map;
 	struct iommu_ctx_ops ops;
 
-	pthread_mutex_t lock;
 	int nranges;
 	struct iommu_iova_range *iova_ranges;
 };

src/iommu/dma.c

@@ -41,7 +41,7 @@ static int iova_cmp(const void *vaddr, const struct skiplist_node *n)
 static int iova_map_add(struct iova_map *map, void *vaddr, size_t len, uint64_t iova,
 			unsigned long flags)
 {
-	__autolock(&map->lock);
+	__autowrlock(&map->lock);
 
 	struct skiplist_node *update[SKIPLIST_LEVELS] = {};
 	struct iova_mapping *m;
@@ -70,7 +70,7 @@ static int iova_map_add(struct iova_map *map, void *vaddr, size_t len, uint64_t
 
 static void iova_map_remove(struct iova_map *map, void *vaddr)
 {
-	__autolock(&map->lock);
+	__autowrlock(&map->lock);
 
 	struct skiplist_node *n, *update[SKIPLIST_LEVELS] = {};
 
@@ -83,15 +83,15 @@ static void iova_map_remove(struct iova_map *map, void *vaddr)
 
 static struct iova_mapping *iova_map_find(struct iova_map *map, void *vaddr)
 {
-	__autolock(&map->lock);
+	__autordlock(&map->lock);
 
 	return container_of_or_null(skiplist_find(&map->list, vaddr, iova_cmp, NULL),
 				    struct iova_mapping, list);
 }
 
 static void iova_map_clear_with(struct iova_map *map, skiplist_iter_fn fn, void *opaque)
 {
-	__autolock(&map->lock);
+	__autowrlock(&map->lock);
 
 	skiplist_clear_with(&map->list, fn, opaque);
 }