diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
index 964ff22..5d5fc75 100644
--- a/drivers/vfio/pci/vfio_pci_config.c
+++ b/drivers/vfio/pci/vfio_pci_config.c
@@ -800,9 +800,6 @@
 	u8 cap;
 	int base = (pos >= PCI_CFG_SPACE_SIZE) ? PCI_CFG_SPACE_SIZE :
 						 PCI_STD_HEADER_SIZEOF;
-	base /= 4;
-	pos /= 4;
-
 	cap = vdev->pci_config_map[pos];
 
 	if (cap == PCI_CAP_ID_BASIC)
@@ -812,7 +809,7 @@
 	while (pos - 1 >= base && vdev->pci_config_map[pos - 1] == cap)
 		pos--;
 
-	return pos * 4;
+	return pos;
 }
 
 static int vfio_msi_config_read(struct vfio_pci_device *vdev, int pos,
@@ -1229,8 +1226,8 @@
 		}
 
 		/* Sanity check, do we overlap other capabilities? */
-		for (i = 0; i < len; i += 4) {
-			if (likely(map[(pos + i) / 4] == PCI_CAP_ID_INVALID))
+		for (i = 0; i < len; i++) {
+			if (likely(map[pos + i] == PCI_CAP_ID_INVALID))
 				continue;
 
 			pr_warn("%s: %s pci config conflict @0x%x, was cap 0x%x now cap 0x%x\n",
@@ -1238,7 +1235,7 @@
 				pos + i, map[pos + i], cap);
 		}
 
-		memset(map + (pos / 4), cap, len / 4);
+		memset(map + pos, cap, len);
 		ret = vfio_fill_vconfig_bytes(vdev, pos, len);
 		if (ret)
 			return ret;
@@ -1313,8 +1310,8 @@
 			hidden = true;
 		}
 
-		for (i = 0; i < len; i += 4) {
-			if (likely(map[(epos + i) / 4] == PCI_CAP_ID_INVALID))
+		for (i = 0; i < len; i++) {
+			if (likely(map[epos + i] == PCI_CAP_ID_INVALID))
 				continue;
 
 			pr_warn("%s: %s pci config conflict @0x%x, was ecap 0x%x now ecap 0x%x\n",
@@ -1329,7 +1326,7 @@
 		 */
 		BUILD_BUG_ON(PCI_EXT_CAP_ID_MAX >= PCI_CAP_ID_INVALID);
 
-		memset(map + (epos / 4), ecap, len / 4);
+		memset(map + epos, ecap, len);
 		ret = vfio_fill_vconfig_bytes(vdev, epos, len);
 		if (ret)
 			return ret;
@@ -1376,10 +1373,12 @@
 	int ret;
 
 	/*
-	 * Config space, caps and ecaps are all dword aligned, so we can
-	 * use one byte per dword to record the type.
+	 * Config space, caps and ecaps are all dword aligned, so we could
+	 * use one byte per dword to record the type.  However, there are
+	 * no requiremenst on the length of a capability, so the gap between
+	 * capabilities needs byte granularity.
 	 */
-	map = kmalloc(pdev->cfg_size / 4, GFP_KERNEL);
+	map = kmalloc(pdev->cfg_size, GFP_KERNEL);
 	if (!map)
 		return -ENOMEM;
 
@@ -1392,9 +1391,9 @@
 	vdev->pci_config_map = map;
 	vdev->vconfig = vconfig;
 
-	memset(map, PCI_CAP_ID_BASIC, PCI_STD_HEADER_SIZEOF / 4);
-	memset(map + (PCI_STD_HEADER_SIZEOF / 4), PCI_CAP_ID_INVALID,
-	       (pdev->cfg_size - PCI_STD_HEADER_SIZEOF) / 4);
+	memset(map, PCI_CAP_ID_BASIC, PCI_STD_HEADER_SIZEOF);
+	memset(map + PCI_STD_HEADER_SIZEOF, PCI_CAP_ID_INVALID,
+	       pdev->cfg_size - PCI_STD_HEADER_SIZEOF);
 
 	ret = vfio_fill_vconfig_bytes(vdev, 0, PCI_STD_HEADER_SIZEOF);
 	if (ret)
@@ -1449,6 +1448,22 @@
 	vdev->msi_perm = NULL;
 }
 
+/*
+ * Find the remaining number of bytes in a dword that match the given
+ * position.  Stop at either the end of the capability or the dword boundary.
+ */
+static size_t vfio_pci_cap_remaining_dword(struct vfio_pci_device *vdev,
+					   loff_t pos)
+{
+	u8 cap = vdev->pci_config_map[pos];
+	size_t i;
+
+	for (i = 1; (pos + i) % 4 && vdev->pci_config_map[pos + i] == cap; i++)
+		/* nop */;
+
+	return i;
+}
+
 static ssize_t vfio_config_do_rw(struct vfio_pci_device *vdev, char __user *buf,
 				 size_t count, loff_t *ppos, bool iswrite)
 {
@@ -1457,19 +1472,27 @@
 	__le32 val = 0;
 	int cap_start = 0, offset;
 	u8 cap_id;
-	ssize_t ret = count;
+	ssize_t ret;
 
-	if (*ppos < 0 || *ppos + count > pdev->cfg_size)
+	if (*ppos < 0 || *ppos >= pdev->cfg_size ||
+	    *ppos + count > pdev->cfg_size)
 		return -EFAULT;
 
 	/*
-	 * gcc can't seem to figure out we're a static function, only called
-	 * with count of 1/2/4 and hits copy_from_user_overflow without this.
+	 * Chop accesses into aligned chunks containing no more than a
+	 * single capability.  Caller increments to the next chunk.
 	 */
-	if (count > sizeof(val))
-		return -EINVAL;
+	count = min(count, vfio_pci_cap_remaining_dword(vdev, *ppos));
+	if (count >= 4 && !(*ppos % 4))
+		count = 4;
+	else if (count >= 2 && !(*ppos % 2))
+		count = 2;
+	else
+		count = 1;
 
-	cap_id = vdev->pci_config_map[*ppos / 4];
+	ret = count;
+
+	cap_id = vdev->pci_config_map[*ppos];
 
 	if (cap_id == PCI_CAP_ID_INVALID) {
 		if (iswrite)
@@ -1485,11 +1508,6 @@
 		return ret;
 	}
 
-	/*
-	 * All capabilities are minimum 4 bytes and aligned on dword
-	 * boundaries.  Since we don't support unaligned accesses, we're
-	 * only ever accessing a single capability.
-	 */
 	if (*ppos >= PCI_CFG_SPACE_SIZE) {
 		WARN_ON(cap_id > PCI_EXT_CAP_ID_MAX);
 
@@ -1545,20 +1563,8 @@
 
 	pos &= VFIO_PCI_OFFSET_MASK;
 
-	/*
-	 * We want to both keep the access size the caller users as well as
-	 * support reading large chunks of config space in a single call.
-	 * PCI doesn't support unaligned accesses, so we can safely break
-	 * those apart.
-	 */
 	while (count) {
-		if (count >= 4 && !(pos % 4))
-			ret = vfio_config_do_rw(vdev, buf, 4, &pos, iswrite);
-		else if (count >= 2 && !(pos % 2))
-			ret = vfio_config_do_rw(vdev, buf, 2, &pos, iswrite);
-		else
-			ret = vfio_config_do_rw(vdev, buf, 1, &pos, iswrite);
-
+		ret = vfio_config_do_rw(vdev, buf, count, &pos, iswrite);
 		if (ret < 0)
 			return ret;