MiniOS + QEMU do not appear to work with either MSI or MSI-X.  Some guests
or device drivers do not gracefully handle being told a PCI device has
MSI/MSI-X and then they don't actually get it.  Disable the MSI and MSI-X
capability reporting in PCI config space, making only INTX legacy interrupts
available.

Signed-off-by: Eric Shelton <eshelton@xxxxxxxxx>

--- a/tools/qemu-xen-traditional/hw/pass-through.c	2016-10-31 12:48:42.924026468 -0400
+++ b/tools/qemu-xen-traditional/hw/pass-through.c	2016-10-31 12:50:52.953026468 -0400
@@ -874,6 +874,10 @@
         .grp_size   = 0x04,
         .size_init  = pt_reg_grp_size_init,
     },
+#ifndef CONFIG_STUBDOM
+    /* At present stubdom doesn't support MSI for passthrough, so let's not
+     * expose MSI capability to stubdom HVM guest for now.
+     */
 #ifndef __ia64__
     /* At present IA64 Xen doesn't support MSI for passthrough, so let's not
      * expose MSI capability to IA64 HVM guest for now.
@@ -886,7 +890,8 @@
         .size_init  = pt_msi_size_init,
         .emu_reg_tbl= pt_emu_reg_msi_tbl,
     },
-#endif
+#endif /* __ia64__ */
+#endif /* !CONFIG_STUBDOM */
     /* PCI-X Capabilities List Item reg group */
     {
         .grp_id     = PCI_CAP_ID_PCIX,
@@ -931,6 +936,10 @@
         .size_init  = pt_pcie_size_init,
         .emu_reg_tbl= pt_emu_reg_pcie_tbl,
     },
+#ifndef CONFIG_STUBDOM
+    /* At present stubdom doesn't support MSI for passthrough, so let's not
+     * expose MSI-X capability to stubdom HVM guest for now.
+     */
 #ifndef __ia64__
     /* At present IA64 Xen doesn't support MSI for passthrough, so let's not
      * expose MSI-X capability to IA64 HVM guest for now.
@@ -943,7 +952,8 @@
         .size_init  = pt_msix_size_init,
         .emu_reg_tbl= pt_emu_reg_msix_tbl,
     },
-#endif
+#endif /* __ia64__ */
+#endif /* !CONFIG_STUBDOM */
     {
         .grp_size = 0,
     },