[Qemu-devel] [PATCH 1/4] hw/pcie: fix Extended Configuration Space for devices with no Extended Capabilities

[Marcel Apfelbaum <marcel@redhat.com>]

Absence of any Extended Capabilities is required to be
indicated by an Extended Capability header with a Capability ID of
0000h, a Capability Version of 0h, and a Next Capability Offset of 000h.

Instead of inserting a 'NULL' capability is simpler to mark the start
of the Extended Configuration Space as read-only to achieve the same
behaviour.

Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
---
 hw/pci/pcie.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
index 99cfb45..62c1def 100644
--- a/hw/pci/pcie.c
+++ b/hw/pci/pcie.c
@@ -109,6 +109,9 @@ int pcie_cap_init(PCIDevice *dev, uint8_t offset, uint8_t type, uint8_t port)
                  PCI_EXP_DEVCAP2_EFF | PCI_EXP_DEVCAP2_EETLPP);
 
     pci_set_word(dev->wmask + pos + PCI_EXP_DEVCTL2, PCI_EXP_DEVCTL2_EETLPPB);
+
+    /* read-only to behave like a 'NULL' Extended Capability Header */
+    pci_set_long(dev->wmask + PCI_CONFIG_SPACE_SIZE, 0);
     return pos;
 }
 
-- 
2.5.5