[Qemu-devel] [PATCH 1/3] virtio: change set guest notifier to per-device

["Michael S. Tsirkin" <mst@redhat.com>]

When using irqfd with vhost-net to inject interrupts,
a single evenfd might inject multiple interrupts.
Implementing this is much easier with a single
per-device callback to set guest notifiers.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/vhost.c      |   52 ++++++++++++++++++++++++++++------------------------
 hw/virtio-pci.c |   29 ++++++++++++++++++++++++++++-
 hw/virtio.h     |    2 +-
 3 files changed, 57 insertions(+), 26 deletions(-)

diff --git a/hw/vhost.c b/hw/vhost.c
index 34c4745..5ac283b 100644
--- a/hw/vhost.c
+++ b/hw/vhost.c
@@ -455,11 +455,6 @@ static int vhost_virtqueue_init(struct vhost_dev *dev,
     };
     struct VirtQueue *vvq = virtio_get_queue(vdev, idx);
 
-    if (!vdev->binding->set_guest_notifier) {
-        fprintf(stderr, "binding does not support guest notifiers\n");
-        return -ENOSYS;
-    }
-
     if (!vdev->binding->set_host_notifier) {
         fprintf(stderr, "binding does not support host notifiers\n");
         return -ENOSYS;
@@ -512,12 +507,6 @@ static int vhost_virtqueue_init(struct vhost_dev *dev,
         r = -errno;
         goto fail_alloc;
     }
-    r = vdev->binding->set_guest_notifier(vdev->binding_opaque, idx, true);
-    if (r < 0) {
-        fprintf(stderr, "Error binding guest notifier: %d\n", -r);
-        goto fail_guest_notifier;
-    }
-
     r = vdev->binding->set_host_notifier(vdev->binding_opaque, idx, true);
     if (r < 0) {
         fprintf(stderr, "Error binding host notifier: %d\n", -r);
@@ -542,8 +531,6 @@ fail_call:
 fail_kick:
     vdev->binding->set_host_notifier(vdev->binding_opaque, idx, false);
 fail_host_notifier:
-    vdev->binding->set_guest_notifier(vdev->binding_opaque, idx, false);
-fail_guest_notifier:
 fail_alloc:
     cpu_physical_memory_unmap(vq->ring, virtio_queue_get_ring_size(vdev, idx),
                               0, 0);
@@ -569,13 +556,6 @@ static void vhost_virtqueue_cleanup(struct vhost_dev *dev,
         .index = idx,
     };
     int r;
-    r = vdev->binding->set_guest_notifier(vdev->binding_opaque, idx, false);
-    if (r < 0) {
-        fprintf(stderr, "vhost VQ %d guest cleanup failed: %d\n", idx, r);
-        fflush(stderr);
-    }
-    assert (r >= 0);
-
     r = vdev->binding->set_host_notifier(vdev->binding_opaque, idx, false);
     if (r < 0) {
         fprintf(stderr, "vhost VQ %d host cleanup failed: %d\n", idx, r);
@@ -648,15 +628,26 @@ void vhost_dev_cleanup(struct vhost_dev *hdev)
 int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
 {
     int i, r;
+    if (!vdev->binding->set_guest_notifiers) {
+        fprintf(stderr, "binding does not support guest notifiers\n");
+        r = -ENOSYS;
+        goto fail;
+    }
+
+    r = vdev->binding->set_guest_notifiers(vdev->binding_opaque, true);
+    if (r < 0) {
+        fprintf(stderr, "Error binding guest notifier: %d\n", -r);
+        goto fail_notifiers;
+    }
 
     r = vhost_dev_set_features(hdev, hdev->log_enabled);
     if (r < 0) {
-        goto fail;
+        goto fail_features;
     }
     r = ioctl(hdev->control, VHOST_SET_MEM_TABLE, hdev->mem);
     if (r < 0) {
         r = -errno;
-        goto fail;
+        goto fail_mem;
     }
     for (i = 0; i < hdev->nvqs; ++i) {
         r = vhost_virtqueue_init(hdev,
@@ -676,13 +667,14 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
                   (uint64_t)(unsigned long)hdev->log);
         if (r < 0) {
             r = -errno;
-            goto fail_vq;
+            goto fail_log;
         }
     }
 
     hdev->started = true;
 
     return 0;
+fail_log:
 fail_vq:
     while (--i >= 0) {
         vhost_virtqueue_cleanup(hdev,
@@ -690,13 +682,18 @@ fail_vq:
                                 hdev->vqs + i,
                                 i);
     }
+fail_mem:
+fail_features:
+    vdev->binding->set_guest_notifiers(vdev->binding_opaque, false);
+fail_notifiers:
 fail:
     return r;
 }
 
 void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev)
 {
-    int i;
+    int i, r;
+
     for (i = 0; i < hdev->nvqs; ++i) {
         vhost_virtqueue_cleanup(hdev,
                                 vdev,
@@ -705,6 +702,13 @@ void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev)
     }
     vhost_client_sync_dirty_bitmap(&hdev->client, 0,
                                    (target_phys_addr_t)~0x0ull);
+    r = vdev->binding->set_guest_notifiers(vdev->binding_opaque, false);
+    if (r < 0) {
+        fprintf(stderr, "vhost guest notifier cleanup failed: %d\n", r);
+        fflush(stderr);
+    }
+    assert (r >= 0);
+
     hdev->started = false;
     qemu_free(hdev->log);
     hdev->log_size = 0;
diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
index 1357d40..232f943 100644
--- a/hw/virtio-pci.c
+++ b/hw/virtio-pci.c
@@ -482,6 +482,33 @@ static int virtio_pci_set_guest_notifier(void *opaque, int n, bool assign)
     return 0;
 }
 
+static int virtio_pci_set_guest_notifiers(void *opaque, bool assign)
+{
+    VirtIOPCIProxy *proxy = opaque;
+    VirtIODevice *vdev = proxy->vdev;
+    int r, n;
+
+    for (n = 0; n < VIRTIO_PCI_QUEUE_MAX; n++) {
+        if (!virtio_queue_get_num(vdev, n)) {
+            break;
+        }
+
+        r = virtio_pci_set_guest_notifier(opaque, n, assign);
+        if (r < 0) {
+            goto assign_error;
+        }
+    }
+
+    return 0;
+
+assign_error:
+    /* We get here on assignment failure. Recover by undoing for VQs 0 .. n. */
+    while (--n >= 0) {
+        virtio_pci_set_guest_notifier(opaque, n, !assign);
+    }
+    return r;
+}
+
 static int virtio_pci_set_host_notifier(void *opaque, int n, bool assign)
 {
     VirtIOPCIProxy *proxy = opaque;
@@ -519,7 +546,7 @@ static const VirtIOBindings virtio_pci_bindings = {
     .load_queue = virtio_pci_load_queue,
     .get_features = virtio_pci_get_features,
     .set_host_notifier = virtio_pci_set_host_notifier,
-    .set_guest_notifier = virtio_pci_set_guest_notifier,
+    .set_guest_notifiers = virtio_pci_set_guest_notifiers,
 };
 
 static void virtio_init_pci(VirtIOPCIProxy *proxy, VirtIODevice *vdev,
diff --git a/hw/virtio.h b/hw/virtio.h
index 5836ab6..457edb2 100644
--- a/hw/virtio.h
+++ b/hw/virtio.h
@@ -92,7 +92,7 @@ typedef struct {
     int (*load_config)(void * opaque, QEMUFile *f);
     int (*load_queue)(void * opaque, int n, QEMUFile *f);
     unsigned (*get_features)(void * opaque);
-    int (*set_guest_notifier)(void * opaque, int n, bool assigned);
+    int (*set_guest_notifiers)(void * opaque, bool assigned);
     int (*set_host_notifier)(void * opaque, int n, bool assigned);
 } VirtIOBindings;
 
-- 
1.7.3-rc1