pci: add API to add capability at a known offset

Unlike virtio, device emulations need to add pci capabilities
at known offsets to match real hardware. Make this possible
by adding an appropriate API.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

2 files changed, 15 insertions, 4 deletions

diff --git a/hw/pci.c b/hw/pci.c
index 0dbca173e3..b6abd67e52 100644
--- a/hw/pci.c
+++ b/hw/pci.c
@@ -1789,12 +1789,10 @@ static int pci_add_option_rom(PCIDevice *pdev)
 }
 
 /* Reserve space and add capability to the linked list in pci config space */
-int pci_add_capability(PCIDevice *pdev, uint8_t cap_id, uint8_t size)
+int pci_add_capability_at_offset(PCIDevice *pdev, uint8_t cap_id,
+                                 uint8_t offset, uint8_t size)
 {
-    uint8_t offset = pci_find_space(pdev, size);
     uint8_t *config = pdev->config + offset;
-    if (!offset)
-        return -ENOSPC;
     config[PCI_CAP_LIST_ID] = cap_id;
     config[PCI_CAP_LIST_NEXT] = pdev->config[PCI_CAPABILITY_LIST];
     pdev->config[PCI_CAPABILITY_LIST] = offset;
@@ -1807,6 +1805,17 @@ int pci_add_capability(PCIDevice *pdev, uint8_t cap_id, uint8_t size)
     return offset;
 }
 
+/* Find and reserve space and add capability to the linked list
+ * in pci config space */
+int pci_add_capability(PCIDevice *pdev, uint8_t cap_id, uint8_t size)
+{
+    uint8_t offset = pci_find_space(pdev, size);
+    if (!offset) {
+        return -ENOSPC;
+    }
+    return pci_add_capability_at_offset(pdev, cap_id, offset, size);
+}
+
 /* Unlink capability from the pci config space. */
 void pci_del_capability(PCIDevice *pdev, uint8_t cap_id, uint8_t size)
 {
diff --git a/hw/pci.h b/hw/pci.h
index 20c670edbb..625188c0e6 100644
--- a/hw/pci.h
+++ b/hw/pci.h
@@ -190,6 +190,8 @@ void pci_register_bar(PCIDevice *pci_dev, int region_num,
                             PCIMapIORegionFunc *map_func);
 
 int pci_add_capability(PCIDevice *pci_dev, uint8_t cap_id, uint8_t cap_size);
+int pci_add_capability_at_offset(PCIDevice *pci_dev, uint8_t cap_id,
+                                 uint8_t cap_offset, uint8_t cap_size);
 
 void pci_del_capability(PCIDevice *pci_dev, uint8_t cap_id, uint8_t cap_size);