diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
index b31107803362..93601407dab8 100644
--- a/drivers/vfio/pci/vfio_pci_config.c
+++ b/drivers/vfio/pci/vfio_pci_config.c
@@ -1149,9 +1149,12 @@ static int vfio_cap_len(struct vfio_pci_device *vdev, u8 cap, u8 pos)
 			return pcibios_err_to_errno(ret);
 
 		if (PCI_X_CMD_VERSION(word)) {
-			/* Test for extended capabilities */
-			pci_read_config_dword(pdev, PCI_CFG_SPACE_SIZE, &dword);
-			vdev->extended_caps = (dword != 0);
+			if (pdev->cfg_size > PCI_CFG_SPACE_SIZE) {
+				/* Test for extended capabilities */
+				pci_read_config_dword(pdev, PCI_CFG_SPACE_SIZE,
+						      &dword);
+				vdev->extended_caps = (dword != 0);
+			}
 			return PCI_CAP_PCIX_SIZEOF_V2;
 		} else
 			return PCI_CAP_PCIX_SIZEOF_V0;
@@ -1163,9 +1166,11 @@ static int vfio_cap_len(struct vfio_pci_device *vdev, u8 cap, u8 pos)
 
 		return byte;
 	case PCI_CAP_ID_EXP:
-		/* Test for extended capabilities */
-		pci_read_config_dword(pdev, PCI_CFG_SPACE_SIZE, &dword);
-		vdev->extended_caps = (dword != 0);
+		if (pdev->cfg_size > PCI_CFG_SPACE_SIZE) {
+			/* Test for extended capabilities */
+			pci_read_config_dword(pdev, PCI_CFG_SPACE_SIZE, &dword);
+			vdev->extended_caps = (dword != 0);
+		}
 
 		/* length based on version */
 		if ((pcie_caps_reg(pdev) & PCI_EXP_FLAGS_VERS) == 1)