virtio_pci: move structure to a header

These are guest/host interfaces, so they belong in the header where e.g.
qemu will know to find them.

Note: we added a new structure as opposed to extending existing one
because someone might be relying on the size of the existing structure
staying unchanged.  Add a warning to avoid using sizeof.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>

drivers/virtio/virtio_pci_modern_dev.c

@@ -294,9 +294,10 @@ int vp_modern_probe(struct virtio_pci_modern_device *mdev)
 
 	err = -EINVAL;
 	mdev->common = vp_modern_map_capability(mdev, common,
-				      sizeof(struct virtio_pci_common_cfg), 4,
-				      0, sizeof(struct virtio_pci_modern_common_cfg),
-				      &mdev->common_len, NULL);
+			      sizeof(struct virtio_pci_common_cfg), 4, 0,
+			      offsetofend(struct virtio_pci_modern_common_cfg,
+					  queue_reset),
+			      &mdev->common_len, NULL);
 	if (!mdev->common)
 		goto err_map_common;
 	mdev->isr = vp_modern_map_capability(mdev, isr, sizeof(u8), 1,

include/linux/virtio_pci_modern.h

@@ -5,13 +5,6 @@
 #include <linux/pci.h>
 #include <linux/virtio_pci.h>
 
-struct virtio_pci_modern_common_cfg {
-	struct virtio_pci_common_cfg cfg;
-
-	__le16 queue_notify_data;	/* read-write */
-	__le16 queue_reset;		/* read-write */
-};
-
 /**
  * struct virtio_pci_modern_device - info for modern PCI virtio
  * @pci_dev:	    Ptr to the PCI device struct

include/uapi/linux/virtio_pci.h

@@ -166,6 +166,17 @@ struct virtio_pci_common_cfg {
 	__le32 queue_used_hi;		/* read-write */
 };
 
+/*
+ * Warning: do not use sizeof on this: use offsetofend for
+ * specific fields you need.
+ */
+struct virtio_pci_modern_common_cfg {
+	struct virtio_pci_common_cfg cfg;
+
+	__le16 queue_notify_data;	/* read-write */
+	__le16 queue_reset;		/* read-write */
+};
+
 /* Fields in VIRTIO_PCI_CAP_PCI_CFG: */
 struct virtio_pci_cfg_cap {
 	struct virtio_pci_cap cap;