[Qemu-devel] [PATCH 1/1] xhci PCIe endpoint migration compatibility fix

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Add back the PCIe config capabilities on XHCI cards in non-PCIe slots,
but only for machine types before 2.1.

This fixes a migration incompatibility in the XHCI PCI devices
caused by:
   058fdcf52cdbf57b67e7 - xhci: add endpoint cap on express bus only

Note that in fixing it for compatibility with older QEMUs, it breaks
compatibility with existing QEMU 2.1's on older machine types.

The status before this patch was (if it used an XHCI adapter):
   machine type | source qemu
     any           pre-2.1     - FAIL
     any           2.1...      - PASS

With this patch:
   machine type | source qemu
     any           pre-2.1    - PASS
     pre-2.1       2.1...     - FAIL
     2.1           2.1...     - PASS

A test to trigger it is to add '-device nec-usb-xhci,id=xhci,addr=0x12'
to the command line.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 hw/usb/hcd-xhci.c    | 6 +++++-
 include/hw/i386/pc.h | 5 +++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/hw/usb/hcd-xhci.c b/hw/usb/hcd-xhci.c
index bbe4c5f..73ced1f 100644
--- a/hw/usb/hcd-xhci.c
+++ b/hw/usb/hcd-xhci.c
@@ -499,6 +499,7 @@ enum xhci_flags {
     XHCI_FLAG_USE_MSI = 1,
     XHCI_FLAG_USE_MSI_X,
     XHCI_FLAG_SS_FIRST,
+    XHCI_FLAG_FORCE_PCIE_ENDCAP,
 };
 
 static void xhci_kick_ep(XHCIState *xhci, unsigned int slotid,
@@ -3626,7 +3627,8 @@ static int usb_xhci_initfn(struct PCIDevice *dev)
                      PCI_BASE_ADDRESS_SPACE_MEMORY|PCI_BASE_ADDRESS_MEM_TYPE_64,
                      &xhci->mem);
 
-    if (pci_bus_is_express(dev->bus)) {
+    if (pci_bus_is_express(dev->bus) ||
+        xhci_get_flag(xhci, XHCI_FLAG_FORCE_PCIE_ENDCAP)) {
         ret = pcie_endpoint_cap_init(dev, 0xa0);
         assert(ret >= 0);
     }
@@ -3855,6 +3857,8 @@ static Property xhci_properties[] = {
     DEFINE_PROP_BIT("msix",     XHCIState, flags, XHCI_FLAG_USE_MSI_X, true),
     DEFINE_PROP_BIT("superspeed-ports-first",
                     XHCIState, flags, XHCI_FLAG_SS_FIRST, true),
+    DEFINE_PROP_BIT("force-pcie-endcap", XHCIState, flags,
+                    XHCI_FLAG_FORCE_PCIE_ENDCAP, false),
     DEFINE_PROP_UINT32("intrs", XHCIState, numintrs, MAXINTRS),
     DEFINE_PROP_UINT32("slots", XHCIState, numslots, MAXSLOTS),
     DEFINE_PROP_UINT32("p2",    XHCIState, numports_2, 4),
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index a39cb42..77316d5 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -330,6 +330,11 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);
             .value    = "off",\
         },\
         {\
+            .driver   = "nec-usb-xhci",\
+            .property = "force-pcie-endcap",\
+            .value    = "on",\
+        },\
+        {\
             .driver   = "pci-serial",\
             .property = "prog_if",\
             .value    = stringify(0),\
-- 
1.9.3