[PATCH 2/2] virtio: fix PCI config err handling

[Luca Boccassi <bluca@debian.org>]

From: Brian Russell <brussell@brocade.com>

In virtio_read_caps, rte_pci_read_config returns the number of bytes
read from PCI config or < 0 on error.
If less than the expected number of bytes are read then log the
failure and return rather than carrying on with garbage.

Signed-off-by: Brian Russell <brussell@brocade.com>
---

Follow-up from:
http://mails.dpdk.org/archives/dev/2017-June/067278.html
https://patches.dpdk.org/patch/25056/

 drivers/net/virtio/virtio_pci.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/net/virtio/virtio_pci.c b/drivers/net/virtio/virtio_pci.c
index 6bd22e54a6..a10698aed8 100644
--- a/drivers/net/virtio/virtio_pci.c
+++ b/drivers/net/virtio/virtio_pci.c
@@ -567,16 +567,18 @@ virtio_read_caps(struct rte_pci_device *dev, struct virtio_hw *hw)
 	}
 
 	ret = rte_pci_read_config(dev, &pos, 1, PCI_CAPABILITY_LIST);
-	if (ret < 0) {
-		PMD_INIT_LOG(DEBUG, "failed to read pci capability list");
+	if (ret != 1) {
+		PMD_INIT_LOG(DEBUG,
+			     "failed to read pci capability list, ret %d", ret);
 		return -1;
 	}
 
 	while (pos) {
 		ret = rte_pci_read_config(dev, &cap, sizeof(cap), pos);
-		if (ret < 0) {
-			PMD_INIT_LOG(ERR,
-				"failed to read pci cap at pos: %x", pos);
+		if (ret != sizeof(cap)) {
+			PMD_INIT_LOG(DEBUG,
+				     "failed to read pci cap at pos: %x ret %d",
+				     pos, ret);
 			break;
 		}
 
-- 
2.18.0