net/virtio: fix descriptor addresses in 32-bit build

[ upstream commit 8c41645be010ec7fa0df4f6c3790b167945154b4 ]

With Virtio-user, the Virtio descriptor buffer address is the
virtual address of the mbuf's buffer. On 32-bit builds, it is
expected to be 32 bits.

With Virtio-PCI, the Virtio descriptor buffer address is the
physical address of the mbuf's buffer. On 32-bit builds running
on 64-bit kernel, it is expected to be up to 64 bits.

This patch introduces a new mask field in virtqueue's struct to
filter our the upper 4 bytes of the address only when necessary.
An optimization is introduced for 64-bit builds to remove the
masking, as the address is always 64 bits wide.

Fixes: ba55c94 ("net/virtio: revert forcing IOVA as VA mode for virtio-user")

Reported-by: Sampath Peechu <[email protected]>
Signed-off-by: Maxime Coquelin <[email protected]>
Reviewed-by: David Marchand <[email protected]>
Signed-off-by: Maxime Coquelin <[email protected]>

.mailmap

@@ -1182,6 +1182,7 @@ Salem Sol <[email protected]>
 Sameh Gobriel <[email protected]>
 Sam Grove <[email protected]>
 Samik Gupta <[email protected]>
+Sampath Peechu <[email protected]>
 Samuel Gauthier <[email protected]>
 Sangjin Han <[email protected]>
 Sankar Chokkalingam <[email protected]>

drivers/net/virtio/virtio_ethdev.c

@@ -638,10 +638,13 @@ virtio_init_queue(struct rte_eth_dev *dev, uint16_t queue_idx)
 		hw->cvq = cvq;
 	}
 
-	if (hw->use_va)
+	if (hw->use_va) {
 		vq->mbuf_addr_offset = offsetof(struct rte_mbuf, buf_addr);
-	else
+		vq->mbuf_addr_mask = UINTPTR_MAX;
+	} else {
 		vq->mbuf_addr_offset = offsetof(struct rte_mbuf, buf_iova);
+		vq->mbuf_addr_mask = UINT64_MAX;
+	}
 
 	if (queue_type == VTNET_TQ) {
 		struct virtio_tx_region *txr;

drivers/net/virtio/virtqueue.h

@@ -113,17 +113,26 @@ virtqueue_store_flags_packed(struct vring_packed_desc *dp,
 
 #define VIRTQUEUE_MAX_NAME_SZ 32
 
+#ifdef RTE_ARCH_32
+#define VIRTIO_MBUF_ADDR_MASK(vq) ((vq)->mbuf_addr_mask)
+#else
+#define VIRTIO_MBUF_ADDR_MASK(vq) UINT64_MAX
+#endif
+
 /**
  * Return the IOVA (or virtual address in case of virtio-user) of mbuf
  * data buffer.
  *
  * The address is firstly casted to the word size (sizeof(uintptr_t))
- * before casting it to uint64_t. This is to make it work with different
- * combination of word size (64 bit and 32 bit) and virtio device
- * (virtio-pci and virtio-user).
+ * before casting it to uint64_t. It is then masked with the expected
+ * address length (64 bits for virtio-pci, word size for virtio-user).
+ *
+ * This is to make it work with different combination of word size (64
+ * bit and 32 bit) and virtio device (virtio-pci and virtio-user).
  */
 #define VIRTIO_MBUF_ADDR(mb, vq) \
-	((uint64_t)(*(uintptr_t *)((uintptr_t)(mb) + (vq)->mbuf_addr_offset)))
+	((*(uint64_t *)((uintptr_t)(mb) + (vq)->mbuf_addr_offset)) & \
+		VIRTIO_MBUF_ADDR_MASK(vq))
 
 /**
  * Return the physical address (or virtual address in case of
@@ -297,6 +306,7 @@ struct virtqueue {
 	void *vq_ring_virt_mem;  /**< linear address of vring*/
 	unsigned int vq_ring_size;
 	uint16_t mbuf_addr_offset;
+	uint64_t mbuf_addr_mask;
 
 	union {
 		struct virtnet_rx rxq;