[Xen-devel] [PATCH RFC 1 6/8] xen/pt: Make xen_pt_unregister_device idempotent

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

To deal with xen_host_pci_[set|get]_ functions returning error values
and clearing ourselves in the init function we should make the
.exit (xen_pt_unregister_device) function be idempotent in case
the generic code starts calling .exit (or for fun does it before
calling .init!).

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 hw/xen/xen-host-pci-device.c |  5 +++++
 hw/xen/xen-host-pci-device.h |  1 +
 hw/xen/xen_pt.c              | 22 ++++++++++++++++------
 hw/xen/xen_pt.h              |  2 ++
 4 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/hw/xen/xen-host-pci-device.c b/hw/xen/xen-host-pci-device.c
index 743b37b..5b20570 100644
--- a/hw/xen/xen-host-pci-device.c
+++ b/hw/xen/xen-host-pci-device.c
@@ -387,6 +387,11 @@ error:
     return rc;
 }
 
+bool xen_host_pci_device_closed(XenHostPCIDevice *d)
+{
+    return d->config_fd == -1;
+}
+
 void xen_host_pci_device_put(XenHostPCIDevice *d)
 {
     if (d->config_fd >= 0) {
diff --git a/hw/xen/xen-host-pci-device.h b/hw/xen/xen-host-pci-device.h
index c2486f0..16f4805 100644
--- a/hw/xen/xen-host-pci-device.h
+++ b/hw/xen/xen-host-pci-device.h
@@ -38,6 +38,7 @@ typedef struct XenHostPCIDevice {
 int xen_host_pci_device_get(XenHostPCIDevice *d, uint16_t domain,
                             uint8_t bus, uint8_t dev, uint8_t func);
 void xen_host_pci_device_put(XenHostPCIDevice *pci_dev);
+bool xen_host_pci_device_closed(XenHostPCIDevice *d);
 
 int xen_host_pci_get_byte(XenHostPCIDevice *d, int pos, uint8_t *p);
 int xen_host_pci_get_word(XenHostPCIDevice *d, int pos, uint16_t *p);
diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
index 2535352..cda6a2d 100644
--- a/hw/xen/xen_pt.c
+++ b/hw/xen/xen_pt.c
@@ -810,6 +810,7 @@ out:
 
     memory_listener_register(&s->memory_listener, &s->dev.bus_master_as);
     memory_listener_register(&s->io_listener, &address_space_io);
+    s->listener_set = true;
     XEN_PT_LOG(d,
                "Real physical device %02x:%02x.%d registered successfully!\n",
                s->hostaddr.bus, s->hostaddr.slot, s->hostaddr.function);
@@ -821,10 +822,13 @@ static void xen_pt_unregister_device(PCIDevice *d)
 {
     XenPCIPassthroughState *s = XEN_PT_DEVICE(d);
     uint8_t machine_irq = s->machine_irq;
-    uint8_t intx = xen_pt_pci_intx(s);
+    uint8_t intx;
     int rc;
 
-    if (machine_irq) {
+     /* Note that if xen_host_pci_device_put had closed config_fd, then
+      * intx value becomes 0xff. */
+    intx = xen_pt_pci_intx(s);
+    if (machine_irq && !xen_host_pci_device_closed(&s->real_device)) {
         rc = xc_domain_unbind_pt_irq(xen_xc, xen_domid, machine_irq,
                                      PT_IRQ_TYPE_PCI,
                                      pci_bus_num(d->bus),
@@ -839,6 +843,7 @@ static void xen_pt_unregister_device(PCIDevice *d)
         }
     }
 
+    /* N.B. xen_pt_config_delete takes care of freeing them. */
     if (s->msi) {
         xen_pt_msi_disable(s);
     }
@@ -858,15 +863,20 @@ static void xen_pt_unregister_device(PCIDevice *d)
                            machine_irq, errno);
             }
         }
+        s->machine_irq = 0;
     }
 
     /* delete all emulated config registers */
     xen_pt_config_delete(s);
 
-    memory_listener_unregister(&s->memory_listener);
-    memory_listener_unregister(&s->io_listener);
-
-    xen_host_pci_device_put(&s->real_device);
+    if (s->listener_set) {
+        memory_listener_unregister(&s->memory_listener);
+        memory_listener_unregister(&s->io_listener);
+        s->listener_set = false;
+    }
+    if (!xen_host_pci_device_closed(&s->real_device)) {
+        xen_host_pci_device_put(&s->real_device);
+    }
 }
 
 static Property xen_pci_passthrough_properties[] = {
diff --git a/hw/xen/xen_pt.h b/hw/xen/xen_pt.h
index 09358b1..98eb74c 100644
--- a/hw/xen/xen_pt.h
+++ b/hw/xen/xen_pt.h
@@ -217,6 +217,7 @@ struct XenPCIPassthroughState {
 
     MemoryListener memory_listener;
     MemoryListener io_listener;
+    bool listener_set;
 };
 
 int xen_pt_config_init(XenPCIPassthroughState *s);
@@ -282,6 +283,7 @@ static inline uint8_t 
xen_pt_pci_intx(XenPCIPassthroughState *s)
                    " value=%i, acceptable range is 1 - 4\n", r_val);
         r_val = 0;
     } else {
+        /* Note that if s.real_device.config_fd is closed we make 0xff. */
         r_val -= 1;
     }
 
-- 
2.1.0


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