[Xen-devel] [PATCH v3] xen_pt: fix failure of attaching & detaching a PCI device to VM repeatedly.

["Jianzhong,Chang" <jianzhongx.chang@xxxxxxxxx>]

 Add pci = [ '$VF_BDF1', '$VF_BDF2', '$VF_BDF3'] in hvm guest configuration 
file.
 After the guest boot up, detach the VFs in sequence by
  "xl pci-detach $DOMID $VF_BDF1"
  "xl pci-detach $DOMID $VF_BDF2"
  "xl pci-detach $DOMID $VF_BDF3"
 and reattach the VFs in sequence by
  "xl pci-attach $DOMID $VF_BDF1"
  "xl pci-attach $DOMID $VF_BDF2"
  "xl pci-attach $DOMID $VF_BDF3"
 An error message will be reported like this:
 "libxl: error: libxl_qmp.c:287:qmp_handle_error_response:
 received an error message from QMP server:
 Duplicate ID 'pci-pt-07_10.1' for device"

When xen_pt_region_add/del() is called,
MemoryRegion may not belong to the XenPCIPassthroughState.
xen_pt_region_update() checks it but memory_region_ref/unref() does not.
This case causes obj->ref issue and affects the release of related objects.
So, memory_region_ref/unref() is moved f
rom xen_pt_region_add/del to xen_pt_region_update.

Signed-off-by: Jianzhong,Chang <jianzhongx.chang@xxxxxxxxx>
---
 hw/xen/xen_pt.c |   16 +++++++++++-----
 1 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
index aa96288..6b72ede 100644
--- a/hw/xen/xen_pt.c
+++ b/hw/xen/xen_pt.c
@@ -591,12 +591,16 @@ static void xen_pt_region_update(XenPCIPassthroughState 
*s,
         return;
     }
 
+    if (adding) {
+        memory_region_ref(sec->mr);
+    }
+
     if (s->msix && &s->msix->mmio == mr) {
         if (adding) {
             s->msix->mmio_base_addr = sec->offset_within_address_space;
             rc = xen_pt_msix_update_remap(s, s->msix->bar_index);
         }
-        return;
+        goto out;
     }
 
     args.type = d->io_regions[bar].type;
@@ -635,6 +639,12 @@ static void xen_pt_region_update(XenPCIPassthroughState *s,
                        adding ? "create new" : "remove old", errno);
         }
     }
+
+out:
+    if (!adding) {
+        memory_region_unref(mr);
+    }
+
 }
 
 static void xen_pt_region_add(MemoryListener *l, MemoryRegionSection *sec)
@@ -642,7 +652,6 @@ static void xen_pt_region_add(MemoryListener *l, 
MemoryRegionSection *sec)
     XenPCIPassthroughState *s = container_of(l, XenPCIPassthroughState,
                                              memory_listener);
 
-    memory_region_ref(sec->mr);
     xen_pt_region_update(s, sec, true);
 }
 
@@ -652,7 +661,6 @@ static void xen_pt_region_del(MemoryListener *l, 
MemoryRegionSection *sec)
                                              memory_listener);
 
     xen_pt_region_update(s, sec, false);
-    memory_region_unref(sec->mr);
 }
 
 static void xen_pt_io_region_add(MemoryListener *l, MemoryRegionSection *sec)
@@ -660,7 +668,6 @@ static void xen_pt_io_region_add(MemoryListener *l, 
MemoryRegionSection *sec)
     XenPCIPassthroughState *s = container_of(l, XenPCIPassthroughState,
                                              io_listener);
 
-    memory_region_ref(sec->mr);
     xen_pt_region_update(s, sec, true);
 }
 
@@ -670,7 +677,6 @@ static void xen_pt_io_region_del(MemoryListener *l, 
MemoryRegionSection *sec)
                                              io_listener);
 
     xen_pt_region_update(s, sec, false);
-    memory_region_unref(sec->mr);
 }
 
 static const MemoryListener xen_pt_memory_listener = {
-- 
1.7.1


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