virtio: fixes, cleanups

Several fixes, most notably fix for virtio on swiotlb systems.
 
 Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

Pull virtio updates from Michael Tsirkin:
 "Several fixes, most notably fix for virtio on swiotlb systems"

* tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost:
  vhost: silence an unused-variable warning
  virtio: hint if callbacks surprisingly might sleep
  virtio-ccw: wire up ->bus_name callback
  s390/virtio: handle find on invalid queue gracefully
  virtio-ccw: diag 500 may return a negative cookie
  virtio_balloon: remove the unnecessary 0-initialization
  virtio-balloon: improve update_balloon_size_func
  virtio-blk: Consider virtio_max_dma_size() for maximum segment size
  virtio: Introduce virtio_max_dma_size()
  dma: Introduce dma_max_mapping_size()
  swiotlb: Add is_swiotlb_active() function
  swiotlb: Introduce swiotlb_max_mapping_size()

Documentation/DMA-API.txt

@@ -195,6 +195,14 @@ Requesting the required mask does not alter the current mask.  If you
 wish to take advantage of it, you should issue a dma_set_mask()
 call to set the mask to the value returned.
 
+::
+
+	size_t
+	dma_direct_max_mapping_size(struct device *dev);
+
+Returns the maximum size of a mapping for the device. The size parameter
+of the mapping functions like dma_map_single(), dma_map_page() and
+others should not be larger than the returned value.
 
 Part Id - Streaming DMA mappings
 --------------------------------

Documentation/virtual/kvm/s390-diag.txt

@@ -68,7 +68,8 @@ Subcode 3 - virtio-ccw notification
     identifier, it is ignored.
 
     After completion of the DIAGNOSE call, general register 2 may contain
-    a 64bit identifier (in the kvm_io_bus cookie case).
+    a 64bit identifier (in the kvm_io_bus cookie case), or a negative
+    error value, if an internal error occurred.
 
     See also the virtio standard for a discussion of this hypercall.
 

drivers/block/virtio_blk.c

@@ -723,7 +723,7 @@ static int virtblk_probe(struct virtio_device *vdev)
 	struct request_queue *q;
 	int err, index;
 
-	u32 v, blk_size, sg_elems, opt_io_size;
+	u32 v, blk_size, max_size, sg_elems, opt_io_size;
 	u16 min_io_size;
 	u8 physical_block_exp, alignment_offset;
 
@@ -826,14 +826,16 @@ static int virtblk_probe(struct virtio_device *vdev)
 	/* No real sector limit. */
 	blk_queue_max_hw_sectors(q, -1U);
 
+	max_size = virtio_max_dma_size(vdev);
+
 	/* Host can optionally specify maximum segment size and number of
 	 * segments. */
 	err = virtio_cread_feature(vdev, VIRTIO_BLK_F_SIZE_MAX,
 				   struct virtio_blk_config, size_max, &v);
 	if (!err)
-		blk_queue_max_segment_size(q, v);
-	else
-		blk_queue_max_segment_size(q, -1U);
+		max_size = min(max_size, v);
+
+	blk_queue_max_segment_size(q, max_size);
 
 	/* Host can optionally specify the block size of the device */
 	err = virtio_cread_feature(vdev, VIRTIO_BLK_F_BLK_SIZE,

drivers/s390/virtio/virtio_ccw.c

@@ -272,6 +272,8 @@ static void virtio_ccw_drop_indicators(struct virtio_ccw_device *vcdev)
 {
 	struct virtio_ccw_vq_info *info;
 
+	if (!vcdev->airq_info)
+		return;
 	list_for_each_entry(info, &vcdev->virtqueues, node)
 		drop_airq_indicator(info->vq, vcdev->airq_info);
 }
@@ -413,7 +415,7 @@ static int virtio_ccw_read_vq_conf(struct virtio_ccw_device *vcdev,
 	ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_READ_VQ_CONF);
 	if (ret)
 		return ret;
-	return vcdev->config_block->num;
+	return vcdev->config_block->num ?: -ENOENT;
 }
 
 static void virtio_ccw_del_vq(struct virtqueue *vq, struct ccw1 *ccw)
@@ -973,6 +975,13 @@ static void virtio_ccw_set_status(struct virtio_device *vdev, u8 status)
 	kfree(ccw);
 }
 
+static const char *virtio_ccw_bus_name(struct virtio_device *vdev)
+{
+	struct virtio_ccw_device *vcdev = to_vc_device(vdev);
+
+	return dev_name(&vcdev->cdev->dev);
+}
+
 static const struct virtio_config_ops virtio_ccw_config_ops = {
 	.get_features = virtio_ccw_get_features,
 	.finalize_features = virtio_ccw_finalize_features,
@@ -983,6 +992,7 @@ static const struct virtio_config_ops virtio_ccw_config_ops = {
 	.reset = virtio_ccw_reset,
 	.find_vqs = virtio_ccw_find_vqs,
 	.del_vqs = virtio_ccw_del_vqs,
+	.bus_name = virtio_ccw_bus_name,
 };
 
 

drivers/vhost/vhost.c

@@ -1188,7 +1188,7 @@ static bool vq_access_ok(struct vhost_virtqueue *vq, unsigned int num,
 			 struct vring_used __user *used)
 
 {
-	size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
+	size_t s __maybe_unused = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 
 	return access_ok(desc, num * sizeof *desc) &&
 	       access_ok(avail,

drivers/virtio/virtio.c

@@ -161,6 +161,7 @@ EXPORT_SYMBOL_GPL(virtio_config_enable);
 
 void virtio_add_status(struct virtio_device *dev, unsigned int status)
 {
+	might_sleep();
 	dev->config->set_status(dev, dev->config->get_status(dev) | status);
 }
 EXPORT_SYMBOL_GPL(virtio_add_status);
@@ -170,6 +171,7 @@ int virtio_finalize_features(struct virtio_device *dev)
 	int ret = dev->config->finalize_features(dev);
 	unsigned status;
 
+	might_sleep();
 	if (ret)
 		return ret;
 

drivers/virtio/virtio_balloon.c

@@ -457,9 +457,12 @@ static void update_balloon_size_func(struct work_struct *work)
 			  update_balloon_size_work);
 	diff = towards_target(vb);
 
+	if (!diff)
+		return;
+
 	if (diff > 0)
 		diff -= fill_balloon(vb, diff);
-	else if (diff < 0)
+	else
 		diff += leak_balloon(vb, -diff);
 	update_balloon_size(vb);
 
@@ -922,7 +925,6 @@ static int virtballoon_probe(struct virtio_device *vdev)
 						  VIRTIO_BALLOON_CMD_ID_STOP);
 		vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,
 						  VIRTIO_BALLOON_CMD_ID_STOP);
-		vb->num_free_page_blocks = 0;
 		spin_lock_init(&vb->free_page_list_lock);
 		INIT_LIST_HEAD(&vb->free_page_list);
 		if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {

drivers/virtio/virtio_ring.c

@@ -271,6 +271,17 @@ static bool vring_use_dma_api(struct virtio_device *vdev)
 	return false;
 }
 
+size_t virtio_max_dma_size(struct virtio_device *vdev)
+{
+	size_t max_segment_size = SIZE_MAX;
+
+	if (vring_use_dma_api(vdev))
+		max_segment_size = dma_max_mapping_size(&vdev->dev);
+
+	return max_segment_size;
+}
+EXPORT_SYMBOL_GPL(virtio_max_dma_size);
+
 static void *vring_alloc_queue(struct virtio_device *vdev, size_t size,
 			      dma_addr_t *dma_handle, gfp_t flag)
 {

include/linux/dma-mapping.h

@@ -130,6 +130,7 @@ struct dma_map_ops {
 			enum dma_data_direction direction);
 	int (*dma_supported)(struct device *dev, u64 mask);
 	u64 (*get_required_mask)(struct device *dev);
+	size_t (*max_mapping_size)(struct device *dev);
 };
 
 #define DMA_MAPPING_ERROR		(~(dma_addr_t)0)
@@ -259,6 +260,8 @@ static inline void dma_direct_sync_sg_for_cpu(struct device *dev,
 }
 #endif
 
+size_t dma_direct_max_mapping_size(struct device *dev);
+
 #ifdef CONFIG_HAS_DMA
 #include <asm/dma-mapping.h>
 
@@ -463,6 +466,7 @@ int dma_supported(struct device *dev, u64 mask);
 int dma_set_mask(struct device *dev, u64 mask);
 int dma_set_coherent_mask(struct device *dev, u64 mask);
 u64 dma_get_required_mask(struct device *dev);
+size_t dma_max_mapping_size(struct device *dev);
 #else /* CONFIG_HAS_DMA */
 static inline dma_addr_t dma_map_page_attrs(struct device *dev,
 		struct page *page, size_t offset, size_t size,
@@ -564,6 +568,10 @@ static inline u64 dma_get_required_mask(struct device *dev)
 {
 	return 0;
 }
+static inline size_t dma_max_mapping_size(struct device *dev)
+{
+	return 0;
+}
 #endif /* CONFIG_HAS_DMA */
 
 static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr,

include/linux/swiotlb.h

@@ -73,6 +73,8 @@ bool swiotlb_map(struct device *dev, phys_addr_t *phys, dma_addr_t *dma_addr,
 		size_t size, enum dma_data_direction dir, unsigned long attrs);
 void __init swiotlb_exit(void);
 unsigned int swiotlb_max_segment(void);
+size_t swiotlb_max_mapping_size(struct device *dev);
+bool is_swiotlb_active(void);
 #else
 #define swiotlb_force SWIOTLB_NO_FORCE
 static inline bool is_swiotlb_buffer(phys_addr_t paddr)
@@ -92,6 +94,15 @@ static inline unsigned int swiotlb_max_segment(void)
 {
 	return 0;
 }
+static inline size_t swiotlb_max_mapping_size(struct device *dev)
+{
+	return SIZE_MAX;
+}
+
+static inline bool is_swiotlb_active(void)
+{
+	return false;
+}
 #endif /* CONFIG_SWIOTLB */
 
 extern void swiotlb_print_info(void);

include/linux/virtio.h

@@ -157,6 +157,8 @@ int virtio_device_freeze(struct virtio_device *dev);
 int virtio_device_restore(struct virtio_device *dev);
 #endif
 
+size_t virtio_max_dma_size(struct virtio_device *vdev);
+
 #define virtio_device_for_each_vq(vdev, vq) \
 	list_for_each_entry(vq, &vdev->vqs, list)
 

include/linux/virtio_config.h

@@ -290,6 +290,7 @@ static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val)
 /* Config space accessors. */
 #define virtio_cread(vdev, structname, member, ptr)			\
 	do {								\
+		might_sleep();						\
 		/* Must match the member's type, and be integer */	\
 		if (!typecheck(typeof((((structname*)0)->member)), *(ptr))) \
 			(*ptr) = 1;					\
@@ -319,6 +320,7 @@ static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val)
 /* Config space accessors. */
 #define virtio_cwrite(vdev, structname, member, ptr)			\
 	do {								\
+		might_sleep();						\
 		/* Must match the member's type, and be integer */	\
 		if (!typecheck(typeof((((structname*)0)->member)), *(ptr))) \
 			BUG_ON((*ptr) == 1);				\
@@ -358,6 +360,7 @@ static inline void __virtio_cread_many(struct virtio_device *vdev,
 		vdev->config->generation(vdev) : 0;
 	int i;
 
+	might_sleep();
 	do {
 		old = gen;
 
@@ -380,6 +383,8 @@ static inline void virtio_cread_bytes(struct virtio_device *vdev,
 static inline u8 virtio_cread8(struct virtio_device *vdev, unsigned int offset)
 {
 	u8 ret;
+
+	might_sleep();
 	vdev->config->get(vdev, offset, &ret, sizeof(ret));
 	return ret;
 }
@@ -387,6 +392,7 @@ static inline u8 virtio_cread8(struct virtio_device *vdev, unsigned int offset)
 static inline void virtio_cwrite8(struct virtio_device *vdev,
 				  unsigned int offset, u8 val)
 {
+	might_sleep();
 	vdev->config->set(vdev, offset, &val, sizeof(val));
 }
 
@@ -394,6 +400,8 @@ static inline u16 virtio_cread16(struct virtio_device *vdev,
 				 unsigned int offset)
 {
 	u16 ret;
+
+	might_sleep();
 	vdev->config->get(vdev, offset, &ret, sizeof(ret));
 	return virtio16_to_cpu(vdev, (__force __virtio16)ret);
 }
@@ -401,6 +409,7 @@ static inline u16 virtio_cread16(struct virtio_device *vdev,
 static inline void virtio_cwrite16(struct virtio_device *vdev,
 				   unsigned int offset, u16 val)
 {
+	might_sleep();
 	val = (__force u16)cpu_to_virtio16(vdev, val);
 	vdev->config->set(vdev, offset, &val, sizeof(val));
 }
@@ -409,6 +418,8 @@ static inline u32 virtio_cread32(struct virtio_device *vdev,
 				 unsigned int offset)
 {
 	u32 ret;
+
+	might_sleep();
 	vdev->config->get(vdev, offset, &ret, sizeof(ret));
 	return virtio32_to_cpu(vdev, (__force __virtio32)ret);
 }
@@ -416,6 +427,7 @@ static inline u32 virtio_cread32(struct virtio_device *vdev,
 static inline void virtio_cwrite32(struct virtio_device *vdev,
 				   unsigned int offset, u32 val)
 {
+	might_sleep();
 	val = (__force u32)cpu_to_virtio32(vdev, val);
 	vdev->config->set(vdev, offset, &val, sizeof(val));
 }
@@ -431,6 +443,7 @@ static inline u64 virtio_cread64(struct virtio_device *vdev,
 static inline void virtio_cwrite64(struct virtio_device *vdev,
 				   unsigned int offset, u64 val)
 {
+	might_sleep();
 	val = (__force u64)cpu_to_virtio64(vdev, val);
 	vdev->config->set(vdev, offset, &val, sizeof(val));
 }

kernel/dma/direct.c

@@ -393,3 +393,14 @@ int dma_direct_supported(struct device *dev, u64 mask)
 	 */
 	return mask >= __phys_to_dma(dev, min_mask);
 }
+
+size_t dma_direct_max_mapping_size(struct device *dev)
+{
+	size_t size = SIZE_MAX;
+
+	/* If SWIOTLB is active, use its maximum mapping size */
+	if (is_swiotlb_active())
+		size = swiotlb_max_mapping_size(dev);
+
+	return size;
+}

kernel/dma/mapping.c

@@ -360,3 +360,17 @@ void dma_cache_sync(struct device *dev, void *vaddr, size_t size,
 		ops->cache_sync(dev, vaddr, size, dir);
 }
 EXPORT_SYMBOL(dma_cache_sync);
+
+size_t dma_max_mapping_size(struct device *dev)
+{
+	const struct dma_map_ops *ops = get_dma_ops(dev);
+	size_t size = SIZE_MAX;
+
+	if (dma_is_direct(ops))
+		size = dma_direct_max_mapping_size(dev);
+	else if (ops && ops->max_mapping_size)
+		size = ops->max_mapping_size(dev);
+
+	return size;
+}
+EXPORT_SYMBOL_GPL(dma_max_mapping_size);

kernel/dma/swiotlb.c

@@ -666,6 +666,20 @@ bool swiotlb_map(struct device *dev, phys_addr_t *phys, dma_addr_t *dma_addr,
 	return true;
 }
 
+size_t swiotlb_max_mapping_size(struct device *dev)
+{
+	return ((size_t)1 << IO_TLB_SHIFT) * IO_TLB_SEGSIZE;
+}
+
+bool is_swiotlb_active(void)
+{
+	/*
+	 * When SWIOTLB is initialized, even if io_tlb_start points to physical
+	 * address zero, io_tlb_end surely doesn't.
+	 */
+	return io_tlb_end != 0;
+}
+
 #ifdef CONFIG_DEBUG_FS
 
 static int __init swiotlb_create_debugfs(void)