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

[Luca Boccassi <bluca@debian.org>]

From: Brian Russell <brussell@brocade.com>

In virtio_read_caps and vtpci_msix_detect, 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.

Fixes: 6ba1f63b5ab0 ("virtio: support specification 1.0")

Signed-off-by: Brian Russell <brussell@brocade.com>
Signed-off-by: Luca Boccassi <bluca@debian.org>
---
v2: handle additional rte_pci_read_config incomplete reads

 drivers/net/virtio/virtio_pci.c | 35 +++++++++++++++++++++------------
 1 file changed, 22 insertions(+), 13 deletions(-)

diff --git a/drivers/net/virtio/virtio_pci.c b/drivers/net/virtio/virtio_pci.c
index 6bd22e54a6..ff6f96f361 100644
--- a/drivers/net/virtio/virtio_pci.c
+++ b/drivers/net/virtio/virtio_pci.c
@@ -560,6 +560,7 @@ virtio_read_caps(struct rte_pci_device *dev, struct virtio_hw *hw)
 	uint8_t pos;
 	struct virtio_pci_cap cap;
 	int ret;
+	uint32_t multiplier;
 
 	if (rte_pci_map_device(dev)) {
 		PMD_INIT_LOG(DEBUG, "failed to map pci device!");
@@ -567,16 +568,18 @@ 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;
 		}
 
@@ -610,9 +613,13 @@ virtio_read_caps(struct rte_pci_device *dev, struct virtio_hw *hw)
 			hw->common_cfg = get_cfg_addr(dev, &cap);
 			break;
 		case VIRTIO_PCI_CAP_NOTIFY_CFG:
-			rte_pci_read_config(dev, &hw->notify_off_multiplier,
-					4, pos + sizeof(cap));
-			hw->notify_base = get_cfg_addr(dev, &cap);
+			/* Avoid half-reads into hw */
+			ret = rte_pci_read_config(dev, &multiplier, 4,
+					pos + sizeof(cap));
+			if (ret == 4) {
+				hw->notify_off_multiplier = multiplier;
+				hw->notify_base = get_cfg_addr(dev, &cap);
+			}
 			break;
 		case VIRTIO_PCI_CAP_DEVICE_CFG:
 			hw->dev_cfg = get_cfg_addr(dev, &cap);
@@ -693,16 +700,18 @@ vtpci_msix_detect(struct rte_pci_device *dev)
 	int ret;
 
 	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 VIRTIO_MSIX_NONE;
 	}
 
 	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