[PATCH 3/3] virtio-pci: Changed return values for "notify", "device" and "isr" read.

[Andrew Melnychenko <andrew@daynix.com>]

Added check for "notify" memory region. Now reads will return "-1" if a virtio
device is not present on a virtio bus.

Signed-off-by: Andrew Melnychenko <andrew@daynix.com>
---
 hw/virtio/virtio-pci.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 186b7bc0f6..447f13beae 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1348,6 +1348,11 @@ static void virtio_pci_common_write(void *opaque, hwaddr addr,
 static uint64_t virtio_pci_notify_read(void *opaque, hwaddr addr,
                                        unsigned size)
 {
+    VirtIOPCIProxy *proxy = opaque;
+    if (virtio_bus_get_device(&proxy->bus) == NULL) {
+        return UINT64_MAX;
+    }
+
     return 0;
 }
 
@@ -1385,7 +1390,7 @@ static uint64_t virtio_pci_isr_read(void *opaque, hwaddr addr,
     uint64_t val;
 
     if (vdev == NULL) {
-        return 0;
+        return UINT64_MAX;
     }
 
     val = qatomic_xchg(&vdev->isr, 0);
@@ -1406,7 +1411,7 @@ static uint64_t virtio_pci_device_read(void *opaque, hwaddr addr,
     uint64_t val;
 
     if (vdev == NULL) {
-        return 0;
+        return UINT64_MAX;
     }
 
     switch (size) {
-- 
2.31.1