[PULL 0/5] virtio: regression fix

[PULL 0/5] virtio: regression fix

[Michael S. Tsirkin]

The following changes since commit b7c61789e653086618d1825858a97b3d9891e822:

  virtio: disable error for out of spec queue-enable (2022-11-22 05:19:00 -0500)

are available in the Git repository at:

  https://git.kernel.org/pub/scm/virt/kvm/mst/qemu.git tags/for_upstream

for you to fetch changes up to 4987e5bf2e9262094fd89d2b8e4d5bd6c4c7312f:

  include/hw: VM state takes precedence in virtio_device_should_start (2022-12-01 02:30:18 -0500)

----------------------------------------------------------------
virtio: regression fix

Fixes regression with migration and vsock, as fixing that
exposes some known issues in vhost user cleanup, this attempts
to fix those as well. More work on vhost user is needed :)

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

----------------------------------------------------------------
Alex Bennée (4):
      tests/qtests: override "force-legacy" for gpio virtio-mmio tests
      hw/virtio: add started_vu status field to vhost-user-gpio
      hw/virtio: generalise CHR_EVENT_CLOSED handling
      include/hw: VM state takes precedence in virtio_device_should_start

Stefano Garzarella (1):
      vhost: enable vrings in vhost_dev_start() for vhost-user devices

 include/hw/virtio/vhost-user-gpio.h | 10 ++++++
 include/hw/virtio/vhost-user.h      | 18 ++++++++++
 include/hw/virtio/vhost.h           |  6 ++--
 include/hw/virtio/virtio.h          | 23 +++++++++---
 backends/cryptodev-vhost.c          |  4 +--
 backends/vhost-user.c               |  4 +--
 hw/block/vhost-user-blk.c           | 45 ++++-------------------
 hw/net/vhost_net.c                  |  8 ++---
 hw/scsi/vhost-scsi-common.c         |  4 +--
 hw/virtio/vhost-user-fs.c           |  4 +--
 hw/virtio/vhost-user-gpio.c         | 30 +++++++++-------
 hw/virtio/vhost-user-i2c.c          |  4 +--
 hw/virtio/vhost-user-rng.c          |  4 +--
 hw/virtio/vhost-user.c              | 71 +++++++++++++++++++++++++++++++++++++
 hw/virtio/vhost-vsock-common.c      |  4 +--
 hw/virtio/vhost.c                   | 44 ++++++++++++++++++++---
 tests/qtest/libqos/virtio-gpio.c    |  3 +-
 hw/virtio/trace-events              |  4 +--
 18 files changed, 207 insertions(+), 83 deletions(-)

[PULL 1/5] tests/qtests: override "force-legacy" for gpio virtio-mmio tests

[Michael S. Tsirkin]

From: Alex Bennée <alex.bennee@linaro.org>

The GPIO device is a VIRTIO_F_VERSION_1 devices but running with a
legacy MMIO interface we miss out that feature bit causing confusion.
For the GPIO test force the mmio bus to support non-legacy so we can
properly test it.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1333
Message-Id: <20221130112439.2527228-2-alex.bennee@linaro.org>
Acked-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 tests/qtest/libqos/virtio-gpio.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tests/qtest/libqos/virtio-gpio.c b/tests/qtest/libqos/virtio-gpio.c
index 762aa6695b..f22d7b5eb5 100644
--- a/tests/qtest/libqos/virtio-gpio.c
+++ b/tests/qtest/libqos/virtio-gpio.c
@@ -154,7 +154,8 @@ static void virtio_gpio_register_nodes(void)
     QOSGraphEdgeOptions edge_opts = { };
 
     /* vhost-user-gpio-device */
-    edge_opts.extra_device_opts = "id=gpio0,chardev=chr-vhost-user-test";
+    edge_opts.extra_device_opts = "id=gpio0,chardev=chr-vhost-user-test "
+        "-global virtio-mmio.force-legacy=false";
     qos_node_create_driver("vhost-user-gpio-device",
                             virtio_gpio_device_create);
     qos_node_consumes("vhost-user-gpio-device", "virtio-bus", &edge_opts);
-- 
MST

[PULL 2/5] vhost: enable vrings in vhost_dev_start() for vhost-user devices

From: Stefano Garzarella <sgarzare@redhat.com>

Commit 02b61f38d3 ("hw/virtio: incorporate backend features in features")
properly negotiates VHOST_USER_F_PROTOCOL_FEATURES with the vhost-user
backend, but we forgot to enable vrings as specified in
docs/interop/vhost-user.rst:

    If ``VHOST_USER_F_PROTOCOL_FEATURES`` has not been negotiated, the
    ring starts directly in the enabled state.

    If ``VHOST_USER_F_PROTOCOL_FEATURES`` has been negotiated, the ring is
    initialized in a disabled state and is enabled by
    ``VHOST_USER_SET_VRING_ENABLE`` with parameter 1.

Some vhost-user front-ends already did this by calling
vhost_ops.vhost_set_vring_enable() directly:
- backends/cryptodev-vhost.c
- hw/net/virtio-net.c
- hw/virtio/vhost-user-gpio.c

But most didn't do that, so we would leave the vrings disabled and some
backends would not work. We observed this issue with the rust version of
virtiofsd [1], which uses the event loop [2] provided by the
vhost-user-backend crate where requests are not processed if vring is
not enabled.

Let's fix this issue by enabling the vrings in vhost_dev_start() for
vhost-user front-ends that don't already do this directly. Same thing
also in vhost_dev_stop() where we disable vrings.

[1] https://gitlab.com/virtio-fs/virtiofsd
[2] https://github.com/rust-vmm/vhost/blob/240fc2966/crates/vhost-user-backend/src/event_loop.rs#L217

Fixes: 02b61f38d3 ("hw/virtio: incorporate backend features in features")
Reported-by: German Maglione <gmaglione@redhat.com>
Tested-by: German Maglione <gmaglione@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Acked-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Message-Id: <20221123131630.52020-1-sgarzare@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20221130112439.2527228-3-alex.bennee@linaro.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/hw/virtio/vhost.h      |  6 +++--
 backends/cryptodev-vhost.c     |  4 ++--
 backends/vhost-user.c          |  4 ++--
 hw/block/vhost-user-blk.c      |  4 ++--
 hw/net/vhost_net.c             |  8 +++----
 hw/scsi/vhost-scsi-common.c    |  4 ++--
 hw/virtio/vhost-user-fs.c      |  4 ++--
 hw/virtio/vhost-user-gpio.c    |  4 ++--
 hw/virtio/vhost-user-i2c.c     |  4 ++--
 hw/virtio/vhost-user-rng.c     |  4 ++--
 hw/virtio/vhost-vsock-common.c |  4 ++--
 hw/virtio/vhost.c              | 44 ++++++++++++++++++++++++++++++----
 hw/virtio/trace-events         |  4 ++--
 13 files changed, 67 insertions(+), 31 deletions(-)

diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index 353252ac3e..67a6807fac 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -184,24 +184,26 @@ static inline bool vhost_dev_is_started(struct vhost_dev *hdev)
  * vhost_dev_start() - start the vhost device
  * @hdev: common vhost_dev structure
  * @vdev: the VirtIODevice structure
+ * @vrings: true to have vrings enabled in this call
  *
  * Starts the vhost device. From this point VirtIO feature negotiation
  * can start and the device can start processing VirtIO transactions.
  *
  * Return: 0 on success, < 0 on error.
  */
-int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev);
+int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev, bool vrings);
 
 /**
  * vhost_dev_stop() - stop the vhost device
  * @hdev: common vhost_dev structure
  * @vdev: the VirtIODevice structure
+ * @vrings: true to have vrings disabled in this call
  *
  * Stop the vhost device. After the device is stopped the notifiers
  * can be disabled (@vhost_dev_disable_notifiers) and the device can
  * be torn down (@vhost_dev_cleanup).
  */
-void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev);
+void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev, bool vrings);
 
 /**
  * DOC: vhost device configuration handling
diff --git a/backends/cryptodev-vhost.c b/backends/cryptodev-vhost.c
index bc13e466b4..572f87b3be 100644
--- a/backends/cryptodev-vhost.c
+++ b/backends/cryptodev-vhost.c
@@ -94,7 +94,7 @@ cryptodev_vhost_start_one(CryptoDevBackendVhost *crypto,
         goto fail_notifiers;
     }
 
-    r = vhost_dev_start(&crypto->dev, dev);
+    r = vhost_dev_start(&crypto->dev, dev, false);
     if (r < 0) {
         goto fail_start;
     }
@@ -111,7 +111,7 @@ static void
 cryptodev_vhost_stop_one(CryptoDevBackendVhost *crypto,
                                  VirtIODevice *dev)
 {
-    vhost_dev_stop(&crypto->dev, dev);
+    vhost_dev_stop(&crypto->dev, dev, false);
     vhost_dev_disable_notifiers(&crypto->dev, dev);
 }
 
diff --git a/backends/vhost-user.c b/backends/vhost-user.c
index 5dedb2d987..7bfcaef976 100644
--- a/backends/vhost-user.c
+++ b/backends/vhost-user.c
@@ -85,7 +85,7 @@ vhost_user_backend_start(VhostUserBackend *b)
     }
 
     b->dev.acked_features = b->vdev->guest_features;
-    ret = vhost_dev_start(&b->dev, b->vdev);
+    ret = vhost_dev_start(&b->dev, b->vdev, true);
     if (ret < 0) {
         error_report("Error start vhost dev");
         goto err_guest_notifiers;
@@ -120,7 +120,7 @@ vhost_user_backend_stop(VhostUserBackend *b)
         return;
     }
 
-    vhost_dev_stop(&b->dev, b->vdev);
+    vhost_dev_stop(&b->dev, b->vdev, true);
 
     if (k->set_guest_notifiers) {
         ret = k->set_guest_notifiers(qbus->parent,
diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index 0d5190accf..1177064631 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -178,7 +178,7 @@ static int vhost_user_blk_start(VirtIODevice *vdev, Error **errp)
     }
 
     s->dev.vq_index_end = s->dev.nvqs;
-    ret = vhost_dev_start(&s->dev, vdev);
+    ret = vhost_dev_start(&s->dev, vdev, true);
     if (ret < 0) {
         error_setg_errno(errp, -ret, "Error starting vhost");
         goto err_guest_notifiers;
@@ -213,7 +213,7 @@ static void vhost_user_blk_stop(VirtIODevice *vdev)
         return;
     }
 
-    vhost_dev_stop(&s->dev, vdev);
+    vhost_dev_stop(&s->dev, vdev, true);
 
     ret = k->set_guest_notifiers(qbus->parent, s->dev.nvqs, false);
     if (ret < 0) {
diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 26e4930676..043058ff43 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -259,7 +259,7 @@ static int vhost_net_start_one(struct vhost_net *net,
         goto fail_notifiers;
     }
 
-    r = vhost_dev_start(&net->dev, dev);
+    r = vhost_dev_start(&net->dev, dev, false);
     if (r < 0) {
         goto fail_start;
     }
@@ -308,7 +308,7 @@ fail:
     if (net->nc->info->poll) {
         net->nc->info->poll(net->nc, true);
     }
-    vhost_dev_stop(&net->dev, dev);
+    vhost_dev_stop(&net->dev, dev, false);
 fail_start:
     vhost_dev_disable_notifiers(&net->dev, dev);
 fail_notifiers:
@@ -329,7 +329,7 @@ static void vhost_net_stop_one(struct vhost_net *net,
     if (net->nc->info->poll) {
         net->nc->info->poll(net->nc, true);
     }
-    vhost_dev_stop(&net->dev, dev);
+    vhost_dev_stop(&net->dev, dev, false);
     if (net->nc->info->stop) {
         net->nc->info->stop(net->nc);
     }
@@ -606,7 +606,7 @@ err_start:
         assert(r >= 0);
     }
 
-    vhost_dev_stop(&net->dev, vdev);
+    vhost_dev_stop(&net->dev, vdev, false);
 
     return r;
 }
diff --git a/hw/scsi/vhost-scsi-common.c b/hw/scsi/vhost-scsi-common.c
index 767f827e55..18ea5dcfa1 100644
--- a/hw/scsi/vhost-scsi-common.c
+++ b/hw/scsi/vhost-scsi-common.c
@@ -68,7 +68,7 @@ int vhost_scsi_common_start(VHostSCSICommon *vsc)
         goto err_guest_notifiers;
     }
 
-    ret = vhost_dev_start(&vsc->dev, vdev);
+    ret = vhost_dev_start(&vsc->dev, vdev, true);
     if (ret < 0) {
         error_report("Error start vhost dev");
         goto err_guest_notifiers;
@@ -101,7 +101,7 @@ void vhost_scsi_common_stop(VHostSCSICommon *vsc)
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
     int ret = 0;
 
-    vhost_dev_stop(&vsc->dev, vdev);
+    vhost_dev_stop(&vsc->dev, vdev, true);
 
     if (k->set_guest_notifiers) {
         ret = k->set_guest_notifiers(qbus->parent, vsc->dev.nvqs, false);
diff --git a/hw/virtio/vhost-user-fs.c b/hw/virtio/vhost-user-fs.c
index dc4014cdef..d97b179e6f 100644
--- a/hw/virtio/vhost-user-fs.c
+++ b/hw/virtio/vhost-user-fs.c
@@ -76,7 +76,7 @@ static void vuf_start(VirtIODevice *vdev)
     }
 
     fs->vhost_dev.acked_features = vdev->guest_features;
-    ret = vhost_dev_start(&fs->vhost_dev, vdev);
+    ret = vhost_dev_start(&fs->vhost_dev, vdev, true);
     if (ret < 0) {
         error_report("Error starting vhost: %d", -ret);
         goto err_guest_notifiers;
@@ -110,7 +110,7 @@ static void vuf_stop(VirtIODevice *vdev)
         return;
     }
 
-    vhost_dev_stop(&fs->vhost_dev, vdev);
+    vhost_dev_stop(&fs->vhost_dev, vdev, true);
 
     ret = k->set_guest_notifiers(qbus->parent, fs->vhost_dev.nvqs, false);
     if (ret < 0) {
diff --git a/hw/virtio/vhost-user-gpio.c b/hw/virtio/vhost-user-gpio.c
index 5851cb3bc9..0b40ebd15a 100644
--- a/hw/virtio/vhost-user-gpio.c
+++ b/hw/virtio/vhost-user-gpio.c
@@ -81,7 +81,7 @@ static int vu_gpio_start(VirtIODevice *vdev)
      */
     vhost_ack_features(&gpio->vhost_dev, feature_bits, vdev->guest_features);
 
-    ret = vhost_dev_start(&gpio->vhost_dev, vdev);
+    ret = vhost_dev_start(&gpio->vhost_dev, vdev, false);
     if (ret < 0) {
         error_report("Error starting vhost-user-gpio: %d", ret);
         goto err_guest_notifiers;
@@ -139,7 +139,7 @@ static void vu_gpio_stop(VirtIODevice *vdev)
         return;
     }
 
-    vhost_dev_stop(vhost_dev, vdev);
+    vhost_dev_stop(vhost_dev, vdev, false);
 
     ret = k->set_guest_notifiers(qbus->parent, vhost_dev->nvqs, false);
     if (ret < 0) {
diff --git a/hw/virtio/vhost-user-i2c.c b/hw/virtio/vhost-user-i2c.c
index 1c9f3d20dc..dc5c828ba6 100644
--- a/hw/virtio/vhost-user-i2c.c
+++ b/hw/virtio/vhost-user-i2c.c
@@ -46,7 +46,7 @@ static void vu_i2c_start(VirtIODevice *vdev)
 
     i2c->vhost_dev.acked_features = vdev->guest_features;
 
-    ret = vhost_dev_start(&i2c->vhost_dev, vdev);
+    ret = vhost_dev_start(&i2c->vhost_dev, vdev, true);
     if (ret < 0) {
         error_report("Error starting vhost-user-i2c: %d", -ret);
         goto err_guest_notifiers;
@@ -80,7 +80,7 @@ static void vu_i2c_stop(VirtIODevice *vdev)
         return;
     }
 
-    vhost_dev_stop(&i2c->vhost_dev, vdev);
+    vhost_dev_stop(&i2c->vhost_dev, vdev, true);
 
     ret = k->set_guest_notifiers(qbus->parent, i2c->vhost_dev.nvqs, false);
     if (ret < 0) {
diff --git a/hw/virtio/vhost-user-rng.c b/hw/virtio/vhost-user-rng.c
index f9084cde58..201a39e220 100644
--- a/hw/virtio/vhost-user-rng.c
+++ b/hw/virtio/vhost-user-rng.c
@@ -47,7 +47,7 @@ static void vu_rng_start(VirtIODevice *vdev)
     }
 
     rng->vhost_dev.acked_features = vdev->guest_features;
-    ret = vhost_dev_start(&rng->vhost_dev, vdev);
+    ret = vhost_dev_start(&rng->vhost_dev, vdev, true);
     if (ret < 0) {
         error_report("Error starting vhost-user-rng: %d", -ret);
         goto err_guest_notifiers;
@@ -81,7 +81,7 @@ static void vu_rng_stop(VirtIODevice *vdev)
         return;
     }
 
-    vhost_dev_stop(&rng->vhost_dev, vdev);
+    vhost_dev_stop(&rng->vhost_dev, vdev, true);
 
     ret = k->set_guest_notifiers(qbus->parent, rng->vhost_dev.nvqs, false);
     if (ret < 0) {
diff --git a/hw/virtio/vhost-vsock-common.c b/hw/virtio/vhost-vsock-common.c
index a67a275de2..d21c72b401 100644
--- a/hw/virtio/vhost-vsock-common.c
+++ b/hw/virtio/vhost-vsock-common.c
@@ -70,7 +70,7 @@ int vhost_vsock_common_start(VirtIODevice *vdev)
     }
 
     vvc->vhost_dev.acked_features = vdev->guest_features;
-    ret = vhost_dev_start(&vvc->vhost_dev, vdev);
+    ret = vhost_dev_start(&vvc->vhost_dev, vdev, true);
     if (ret < 0) {
         error_report("Error starting vhost: %d", -ret);
         goto err_guest_notifiers;
@@ -105,7 +105,7 @@ void vhost_vsock_common_stop(VirtIODevice *vdev)
         return;
     }
 
-    vhost_dev_stop(&vvc->vhost_dev, vdev);
+    vhost_dev_stop(&vvc->vhost_dev, vdev, true);
 
     ret = k->set_guest_notifiers(qbus->parent, vvc->vhost_dev.nvqs, false);
     if (ret < 0) {
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index d1c4c20b8c..7fb008bc9e 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1777,15 +1777,36 @@ int vhost_dev_get_inflight(struct vhost_dev *dev, uint16_t queue_size,
     return 0;
 }
 
+static int vhost_dev_set_vring_enable(struct vhost_dev *hdev, int enable)
+{
+    if (!hdev->vhost_ops->vhost_set_vring_enable) {
+        return 0;
+    }
+
+    /*
+     * For vhost-user devices, if VHOST_USER_F_PROTOCOL_FEATURES has not
+     * been negotiated, the rings start directly in the enabled state, and
+     * .vhost_set_vring_enable callback will fail since
+     * VHOST_USER_SET_VRING_ENABLE is not supported.
+     */
+    if (hdev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER &&
+        !virtio_has_feature(hdev->backend_features,
+                            VHOST_USER_F_PROTOCOL_FEATURES)) {
+        return 0;
+    }
+
+    return hdev->vhost_ops->vhost_set_vring_enable(hdev, enable);
+}
+
 /* Host notifiers must be enabled at this point. */
-int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
+int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev, bool vrings)
 {
     int i, r;
 
     /* should only be called after backend is connected */
     assert(hdev->vhost_ops);
 
-    trace_vhost_dev_start(hdev, vdev->name);
+    trace_vhost_dev_start(hdev, vdev->name, vrings);
 
     vdev->vhost_started = true;
     hdev->started = true;
@@ -1830,10 +1851,16 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
             goto fail_log;
         }
     }
+    if (vrings) {
+        r = vhost_dev_set_vring_enable(hdev, true);
+        if (r) {
+            goto fail_log;
+        }
+    }
     if (hdev->vhost_ops->vhost_dev_start) {
         r = hdev->vhost_ops->vhost_dev_start(hdev, true);
         if (r) {
-            goto fail_log;
+            goto fail_start;
         }
     }
     if (vhost_dev_has_iommu(hdev) &&
@@ -1848,6 +1875,10 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
         }
     }
     return 0;
+fail_start:
+    if (vrings) {
+        vhost_dev_set_vring_enable(hdev, false);
+    }
 fail_log:
     vhost_log_put(hdev, false);
 fail_vq:
@@ -1866,18 +1897,21 @@ fail_features:
 }
 
 /* Host notifiers must be enabled at this point. */
-void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev)
+void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev, bool vrings)
 {
     int i;
 
     /* should only be called after backend is connected */
     assert(hdev->vhost_ops);
 
-    trace_vhost_dev_stop(hdev, vdev->name);
+    trace_vhost_dev_stop(hdev, vdev->name, vrings);
 
     if (hdev->vhost_ops->vhost_dev_start) {
         hdev->vhost_ops->vhost_dev_start(hdev, false);
     }
+    if (vrings) {
+        vhost_dev_set_vring_enable(hdev, false);
+    }
     for (i = 0; i < hdev->nvqs; ++i) {
         vhost_virtqueue_stop(hdev,
                              vdev,
diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
index 820dadc26c..14fc5b9bb2 100644
--- a/hw/virtio/trace-events
+++ b/hw/virtio/trace-events
@@ -9,8 +9,8 @@ vhost_section(const char *name) "%s"
 vhost_reject_section(const char *name, int d) "%s:%d"
 vhost_iotlb_miss(void *dev, int step) "%p step %d"
 vhost_dev_cleanup(void *dev) "%p"
-vhost_dev_start(void *dev, const char *name) "%p:%s"
-vhost_dev_stop(void *dev, const char *name) "%p:%s"
+vhost_dev_start(void *dev, const char *name, bool vrings) "%p:%s vrings:%d"
+vhost_dev_stop(void *dev, const char *name, bool vrings) "%p:%s vrings:%d"
 
 
 # vhost-user.c
-- 
MST

[Virtio-fs] [PULL 2/5] vhost: enable vrings in vhost_dev_start() for vhost-user devices

[Michael S. Tsirkin]

From: Stefano Garzarella <sgarzare@redhat.com>

Commit 02b61f38d3 ("hw/virtio: incorporate backend features in features")
properly negotiates VHOST_USER_F_PROTOCOL_FEATURES with the vhost-user
backend, but we forgot to enable vrings as specified in
docs/interop/vhost-user.rst:

    If ``VHOST_USER_F_PROTOCOL_FEATURES`` has not been negotiated, the
    ring starts directly in the enabled state.

    If ``VHOST_USER_F_PROTOCOL_FEATURES`` has been negotiated, the ring is
    initialized in a disabled state and is enabled by
    ``VHOST_USER_SET_VRING_ENABLE`` with parameter 1.

Some vhost-user front-ends already did this by calling
vhost_ops.vhost_set_vring_enable() directly:
- backends/cryptodev-vhost.c
- hw/net/virtio-net.c
- hw/virtio/vhost-user-gpio.c

But most didn't do that, so we would leave the vrings disabled and some
backends would not work. We observed this issue with the rust version of
virtiofsd [1], which uses the event loop [2] provided by the
vhost-user-backend crate where requests are not processed if vring is
not enabled.

Let's fix this issue by enabling the vrings in vhost_dev_start() for
vhost-user front-ends that don't already do this directly. Same thing
also in vhost_dev_stop() where we disable vrings.

[1] https://gitlab.com/virtio-fs/virtiofsd
[2] https://github.com/rust-vmm/vhost/blob/240fc2966/crates/vhost-user-backend/src/event_loop.rs#L217

Fixes: 02b61f38d3 ("hw/virtio: incorporate backend features in features")
Reported-by: German Maglione <gmaglione@redhat.com>
Tested-by: German Maglione <gmaglione@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Acked-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Message-Id: <20221123131630.52020-1-sgarzare@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20221130112439.2527228-3-alex.bennee@linaro.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/hw/virtio/vhost.h      |  6 +++--
 backends/cryptodev-vhost.c     |  4 ++--
 backends/vhost-user.c          |  4 ++--
 hw/block/vhost-user-blk.c      |  4 ++--
 hw/net/vhost_net.c             |  8 +++----
 hw/scsi/vhost-scsi-common.c    |  4 ++--
 hw/virtio/vhost-user-fs.c      |  4 ++--
 hw/virtio/vhost-user-gpio.c    |  4 ++--
 hw/virtio/vhost-user-i2c.c     |  4 ++--
 hw/virtio/vhost-user-rng.c     |  4 ++--
 hw/virtio/vhost-vsock-common.c |  4 ++--
 hw/virtio/vhost.c              | 44 ++++++++++++++++++++++++++++++----
 hw/virtio/trace-events         |  4 ++--
 13 files changed, 67 insertions(+), 31 deletions(-)

diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index 353252ac3e..67a6807fac 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -184,24 +184,26 @@ static inline bool vhost_dev_is_started(struct vhost_dev *hdev)
  * vhost_dev_start() - start the vhost device
  * @hdev: common vhost_dev structure
  * @vdev: the VirtIODevice structure
+ * @vrings: true to have vrings enabled in this call
  *
  * Starts the vhost device. From this point VirtIO feature negotiation
  * can start and the device can start processing VirtIO transactions.
  *
  * Return: 0 on success, < 0 on error.
  */
-int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev);
+int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev, bool vrings);
 
 /**
  * vhost_dev_stop() - stop the vhost device
  * @hdev: common vhost_dev structure
  * @vdev: the VirtIODevice structure
+ * @vrings: true to have vrings disabled in this call
  *
  * Stop the vhost device. After the device is stopped the notifiers
  * can be disabled (@vhost_dev_disable_notifiers) and the device can
  * be torn down (@vhost_dev_cleanup).
  */
-void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev);
+void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev, bool vrings);
 
 /**
  * DOC: vhost device configuration handling
diff --git a/backends/cryptodev-vhost.c b/backends/cryptodev-vhost.c
index bc13e466b4..572f87b3be 100644
--- a/backends/cryptodev-vhost.c
+++ b/backends/cryptodev-vhost.c
@@ -94,7 +94,7 @@ cryptodev_vhost_start_one(CryptoDevBackendVhost *crypto,
         goto fail_notifiers;
     }
 
-    r = vhost_dev_start(&crypto->dev, dev);
+    r = vhost_dev_start(&crypto->dev, dev, false);
     if (r < 0) {
         goto fail_start;
     }
@@ -111,7 +111,7 @@ static void
 cryptodev_vhost_stop_one(CryptoDevBackendVhost *crypto,
                                  VirtIODevice *dev)
 {
-    vhost_dev_stop(&crypto->dev, dev);
+    vhost_dev_stop(&crypto->dev, dev, false);
     vhost_dev_disable_notifiers(&crypto->dev, dev);
 }
 
diff --git a/backends/vhost-user.c b/backends/vhost-user.c
index 5dedb2d987..7bfcaef976 100644
--- a/backends/vhost-user.c
+++ b/backends/vhost-user.c
@@ -85,7 +85,7 @@ vhost_user_backend_start(VhostUserBackend *b)
     }
 
     b->dev.acked_features = b->vdev->guest_features;
-    ret = vhost_dev_start(&b->dev, b->vdev);
+    ret = vhost_dev_start(&b->dev, b->vdev, true);
     if (ret < 0) {
         error_report("Error start vhost dev");
         goto err_guest_notifiers;
@@ -120,7 +120,7 @@ vhost_user_backend_stop(VhostUserBackend *b)
         return;
     }
 
-    vhost_dev_stop(&b->dev, b->vdev);
+    vhost_dev_stop(&b->dev, b->vdev, true);
 
     if (k->set_guest_notifiers) {
         ret = k->set_guest_notifiers(qbus->parent,
diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index 0d5190accf..1177064631 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -178,7 +178,7 @@ static int vhost_user_blk_start(VirtIODevice *vdev, Error **errp)
     }
 
     s->dev.vq_index_end = s->dev.nvqs;
-    ret = vhost_dev_start(&s->dev, vdev);
+    ret = vhost_dev_start(&s->dev, vdev, true);
     if (ret < 0) {
         error_setg_errno(errp, -ret, "Error starting vhost");
         goto err_guest_notifiers;
@@ -213,7 +213,7 @@ static void vhost_user_blk_stop(VirtIODevice *vdev)
         return;
     }
 
-    vhost_dev_stop(&s->dev, vdev);
+    vhost_dev_stop(&s->dev, vdev, true);
 
     ret = k->set_guest_notifiers(qbus->parent, s->dev.nvqs, false);
     if (ret < 0) {
diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 26e4930676..043058ff43 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -259,7 +259,7 @@ static int vhost_net_start_one(struct vhost_net *net,
         goto fail_notifiers;
     }
 
-    r = vhost_dev_start(&net->dev, dev);
+    r = vhost_dev_start(&net->dev, dev, false);
     if (r < 0) {
         goto fail_start;
     }
@@ -308,7 +308,7 @@ fail:
     if (net->nc->info->poll) {
         net->nc->info->poll(net->nc, true);
     }
-    vhost_dev_stop(&net->dev, dev);
+    vhost_dev_stop(&net->dev, dev, false);
 fail_start:
     vhost_dev_disable_notifiers(&net->dev, dev);
 fail_notifiers:
@@ -329,7 +329,7 @@ static void vhost_net_stop_one(struct vhost_net *net,
     if (net->nc->info->poll) {
         net->nc->info->poll(net->nc, true);
     }
-    vhost_dev_stop(&net->dev, dev);
+    vhost_dev_stop(&net->dev, dev, false);
     if (net->nc->info->stop) {
         net->nc->info->stop(net->nc);
     }
@@ -606,7 +606,7 @@ err_start:
         assert(r >= 0);
     }
 
-    vhost_dev_stop(&net->dev, vdev);
+    vhost_dev_stop(&net->dev, vdev, false);
 
     return r;
 }
diff --git a/hw/scsi/vhost-scsi-common.c b/hw/scsi/vhost-scsi-common.c
index 767f827e55..18ea5dcfa1 100644
--- a/hw/scsi/vhost-scsi-common.c
+++ b/hw/scsi/vhost-scsi-common.c
@@ -68,7 +68,7 @@ int vhost_scsi_common_start(VHostSCSICommon *vsc)
         goto err_guest_notifiers;
     }
 
-    ret = vhost_dev_start(&vsc->dev, vdev);
+    ret = vhost_dev_start(&vsc->dev, vdev, true);
     if (ret < 0) {
         error_report("Error start vhost dev");
         goto err_guest_notifiers;
@@ -101,7 +101,7 @@ void vhost_scsi_common_stop(VHostSCSICommon *vsc)
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
     int ret = 0;
 
-    vhost_dev_stop(&vsc->dev, vdev);
+    vhost_dev_stop(&vsc->dev, vdev, true);
 
     if (k->set_guest_notifiers) {
         ret = k->set_guest_notifiers(qbus->parent, vsc->dev.nvqs, false);
diff --git a/hw/virtio/vhost-user-fs.c b/hw/virtio/vhost-user-fs.c
index dc4014cdef..d97b179e6f 100644
--- a/hw/virtio/vhost-user-fs.c
+++ b/hw/virtio/vhost-user-fs.c
@@ -76,7 +76,7 @@ static void vuf_start(VirtIODevice *vdev)
     }
 
     fs->vhost_dev.acked_features = vdev->guest_features;
-    ret = vhost_dev_start(&fs->vhost_dev, vdev);
+    ret = vhost_dev_start(&fs->vhost_dev, vdev, true);
     if (ret < 0) {
         error_report("Error starting vhost: %d", -ret);
         goto err_guest_notifiers;
@@ -110,7 +110,7 @@ static void vuf_stop(VirtIODevice *vdev)
         return;
     }
 
-    vhost_dev_stop(&fs->vhost_dev, vdev);
+    vhost_dev_stop(&fs->vhost_dev, vdev, true);
 
     ret = k->set_guest_notifiers(qbus->parent, fs->vhost_dev.nvqs, false);
     if (ret < 0) {
diff --git a/hw/virtio/vhost-user-gpio.c b/hw/virtio/vhost-user-gpio.c
index 5851cb3bc9..0b40ebd15a 100644
--- a/hw/virtio/vhost-user-gpio.c
+++ b/hw/virtio/vhost-user-gpio.c
@@ -81,7 +81,7 @@ static int vu_gpio_start(VirtIODevice *vdev)
      */
     vhost_ack_features(&gpio->vhost_dev, feature_bits, vdev->guest_features);
 
-    ret = vhost_dev_start(&gpio->vhost_dev, vdev);
+    ret = vhost_dev_start(&gpio->vhost_dev, vdev, false);
     if (ret < 0) {
         error_report("Error starting vhost-user-gpio: %d", ret);
         goto err_guest_notifiers;
@@ -139,7 +139,7 @@ static void vu_gpio_stop(VirtIODevice *vdev)
         return;
     }
 
-    vhost_dev_stop(vhost_dev, vdev);
+    vhost_dev_stop(vhost_dev, vdev, false);
 
     ret = k->set_guest_notifiers(qbus->parent, vhost_dev->nvqs, false);
     if (ret < 0) {
diff --git a/hw/virtio/vhost-user-i2c.c b/hw/virtio/vhost-user-i2c.c
index 1c9f3d20dc..dc5c828ba6 100644
--- a/hw/virtio/vhost-user-i2c.c
+++ b/hw/virtio/vhost-user-i2c.c
@@ -46,7 +46,7 @@ static void vu_i2c_start(VirtIODevice *vdev)
 
     i2c->vhost_dev.acked_features = vdev->guest_features;
 
-    ret = vhost_dev_start(&i2c->vhost_dev, vdev);
+    ret = vhost_dev_start(&i2c->vhost_dev, vdev, true);
     if (ret < 0) {
         error_report("Error starting vhost-user-i2c: %d", -ret);
         goto err_guest_notifiers;
@@ -80,7 +80,7 @@ static void vu_i2c_stop(VirtIODevice *vdev)
         return;
     }
 
-    vhost_dev_stop(&i2c->vhost_dev, vdev);
+    vhost_dev_stop(&i2c->vhost_dev, vdev, true);
 
     ret = k->set_guest_notifiers(qbus->parent, i2c->vhost_dev.nvqs, false);
     if (ret < 0) {
diff --git a/hw/virtio/vhost-user-rng.c b/hw/virtio/vhost-user-rng.c
index f9084cde58..201a39e220 100644
--- a/hw/virtio/vhost-user-rng.c
+++ b/hw/virtio/vhost-user-rng.c
@@ -47,7 +47,7 @@ static void vu_rng_start(VirtIODevice *vdev)
     }
 
     rng->vhost_dev.acked_features = vdev->guest_features;
-    ret = vhost_dev_start(&rng->vhost_dev, vdev);
+    ret = vhost_dev_start(&rng->vhost_dev, vdev, true);
     if (ret < 0) {
         error_report("Error starting vhost-user-rng: %d", -ret);
         goto err_guest_notifiers;
@@ -81,7 +81,7 @@ static void vu_rng_stop(VirtIODevice *vdev)
         return;
     }
 
-    vhost_dev_stop(&rng->vhost_dev, vdev);
+    vhost_dev_stop(&rng->vhost_dev, vdev, true);
 
     ret = k->set_guest_notifiers(qbus->parent, rng->vhost_dev.nvqs, false);
     if (ret < 0) {
diff --git a/hw/virtio/vhost-vsock-common.c b/hw/virtio/vhost-vsock-common.c
index a67a275de2..d21c72b401 100644
--- a/hw/virtio/vhost-vsock-common.c
+++ b/hw/virtio/vhost-vsock-common.c
@@ -70,7 +70,7 @@ int vhost_vsock_common_start(VirtIODevice *vdev)
     }
 
     vvc->vhost_dev.acked_features = vdev->guest_features;
-    ret = vhost_dev_start(&vvc->vhost_dev, vdev);
+    ret = vhost_dev_start(&vvc->vhost_dev, vdev, true);
     if (ret < 0) {
         error_report("Error starting vhost: %d", -ret);
         goto err_guest_notifiers;
@@ -105,7 +105,7 @@ void vhost_vsock_common_stop(VirtIODevice *vdev)
         return;
     }
 
-    vhost_dev_stop(&vvc->vhost_dev, vdev);
+    vhost_dev_stop(&vvc->vhost_dev, vdev, true);
 
     ret = k->set_guest_notifiers(qbus->parent, vvc->vhost_dev.nvqs, false);
     if (ret < 0) {
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index d1c4c20b8c..7fb008bc9e 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1777,15 +1777,36 @@ int vhost_dev_get_inflight(struct vhost_dev *dev, uint16_t queue_size,
     return 0;
 }
 
+static int vhost_dev_set_vring_enable(struct vhost_dev *hdev, int enable)
+{
+    if (!hdev->vhost_ops->vhost_set_vring_enable) {
+        return 0;
+    }
+
+    /*
+     * For vhost-user devices, if VHOST_USER_F_PROTOCOL_FEATURES has not
+     * been negotiated, the rings start directly in the enabled state, and
+     * .vhost_set_vring_enable callback will fail since
+     * VHOST_USER_SET_VRING_ENABLE is not supported.
+     */
+    if (hdev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER &&
+        !virtio_has_feature(hdev->backend_features,
+                            VHOST_USER_F_PROTOCOL_FEATURES)) {
+        return 0;
+    }
+
+    return hdev->vhost_ops->vhost_set_vring_enable(hdev, enable);
+}
+
 /* Host notifiers must be enabled at this point. */
-int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
+int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev, bool vrings)
 {
     int i, r;
 
     /* should only be called after backend is connected */
     assert(hdev->vhost_ops);
 
-    trace_vhost_dev_start(hdev, vdev->name);
+    trace_vhost_dev_start(hdev, vdev->name, vrings);
 
     vdev->vhost_started = true;
     hdev->started = true;
@@ -1830,10 +1851,16 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
             goto fail_log;
         }
     }
+    if (vrings) {
+        r = vhost_dev_set_vring_enable(hdev, true);
+        if (r) {
+            goto fail_log;
+        }
+    }
     if (hdev->vhost_ops->vhost_dev_start) {
         r = hdev->vhost_ops->vhost_dev_start(hdev, true);
         if (r) {
-            goto fail_log;
+            goto fail_start;
         }
     }
     if (vhost_dev_has_iommu(hdev) &&
@@ -1848,6 +1875,10 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
         }
     }
     return 0;
+fail_start:
+    if (vrings) {
+        vhost_dev_set_vring_enable(hdev, false);
+    }
 fail_log:
     vhost_log_put(hdev, false);
 fail_vq:
@@ -1866,18 +1897,21 @@ fail_features:
 }
 
 /* Host notifiers must be enabled at this point. */
-void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev)
+void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev, bool vrings)
 {
     int i;
 
     /* should only be called after backend is connected */
     assert(hdev->vhost_ops);
 
-    trace_vhost_dev_stop(hdev, vdev->name);
+    trace_vhost_dev_stop(hdev, vdev->name, vrings);
 
     if (hdev->vhost_ops->vhost_dev_start) {
         hdev->vhost_ops->vhost_dev_start(hdev, false);
     }
+    if (vrings) {
+        vhost_dev_set_vring_enable(hdev, false);
+    }
     for (i = 0; i < hdev->nvqs; ++i) {
         vhost_virtqueue_stop(hdev,
                              vdev,
diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
index 820dadc26c..14fc5b9bb2 100644
--- a/hw/virtio/trace-events
+++ b/hw/virtio/trace-events
@@ -9,8 +9,8 @@ vhost_section(const char *name) "%s"
 vhost_reject_section(const char *name, int d) "%s:%d"
 vhost_iotlb_miss(void *dev, int step) "%p step %d"
 vhost_dev_cleanup(void *dev) "%p"
-vhost_dev_start(void *dev, const char *name) "%p:%s"
-vhost_dev_stop(void *dev, const char *name) "%p:%s"
+vhost_dev_start(void *dev, const char *name, bool vrings) "%p:%s vrings:%d"
+vhost_dev_stop(void *dev, const char *name, bool vrings) "%p:%s vrings:%d"
 
 
 # vhost-user.c
-- 
MST

[PULL 4/5] hw/virtio: generalise CHR_EVENT_CLOSED handling

[Michael S. Tsirkin]

From: Alex Bennée <alex.bennee@linaro.org>

..and use for both virtio-user-blk and virtio-user-gpio. This avoids
the circular close by deferring shutdown due to disconnection until a
later point. virtio-user-blk already had this mechanism in place so
generalise it as a vhost-user helper function and use for both blk and
gpio devices.

While we are at it we also fix up vhost-user-gpio to re-establish the
event handler after close down so we can reconnect later.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Message-Id: <20221130112439.2527228-5-alex.bennee@linaro.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/hw/virtio/vhost-user.h | 18 +++++++++
 hw/block/vhost-user-blk.c      | 41 +++-----------------
 hw/virtio/vhost-user-gpio.c    | 11 +++++-
 hw/virtio/vhost-user.c         | 71 ++++++++++++++++++++++++++++++++++
 4 files changed, 104 insertions(+), 37 deletions(-)

diff --git a/include/hw/virtio/vhost-user.h b/include/hw/virtio/vhost-user.h
index c6e693cd3f..191216a74f 100644
--- a/include/hw/virtio/vhost-user.h
+++ b/include/hw/virtio/vhost-user.h
@@ -68,4 +68,22 @@ bool vhost_user_init(VhostUserState *user, CharBackend *chr, Error **errp);
  */
 void vhost_user_cleanup(VhostUserState *user);
 
+/**
+ * vhost_user_async_close() - cleanup vhost-user post connection drop
+ * @d: DeviceState for the associated device (passed to callback)
+ * @chardev: the CharBackend associated with the connection
+ * @vhost: the common vhost device
+ * @cb: the user callback function to complete the clean-up
+ *
+ * This function is used to handle the shutdown of a vhost-user
+ * connection to a backend. We handle this centrally to make sure we
+ * do all the steps and handle potential races due to VM shutdowns.
+ * Once the connection is disabled we call a backhalf to ensure
+ */
+typedef void (*vu_async_close_fn)(DeviceState *cb);
+
+void vhost_user_async_close(DeviceState *d,
+                            CharBackend *chardev, struct vhost_dev *vhost,
+                            vu_async_close_fn cb);
+
 #endif
diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index 1177064631..aff4d2b8cb 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -369,17 +369,10 @@ static void vhost_user_blk_disconnect(DeviceState *dev)
     vhost_user_blk_stop(vdev);
 
     vhost_dev_cleanup(&s->dev);
-}
 
-static void vhost_user_blk_chr_closed_bh(void *opaque)
-{
-    DeviceState *dev = opaque;
-    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
-    VHostUserBlk *s = VHOST_USER_BLK(vdev);
-
-    vhost_user_blk_disconnect(dev);
+    /* Re-instate the event handler for new connections */
     qemu_chr_fe_set_handlers(&s->chardev, NULL, NULL, vhost_user_blk_event,
-                             NULL, opaque, NULL, true);
+                             NULL, dev, NULL, true);
 }
 
 static void vhost_user_blk_event(void *opaque, QEMUChrEvent event)
@@ -398,33 +391,9 @@ static void vhost_user_blk_event(void *opaque, QEMUChrEvent event)
         }
         break;
     case CHR_EVENT_CLOSED:
-        if (!runstate_check(RUN_STATE_SHUTDOWN)) {
-            /*
-             * A close event may happen during a read/write, but vhost
-             * code assumes the vhost_dev remains setup, so delay the
-             * stop & clear.
-             */
-            AioContext *ctx = qemu_get_current_aio_context();
-
-            qemu_chr_fe_set_handlers(&s->chardev, NULL, NULL, NULL, NULL,
-                    NULL, NULL, false);
-            aio_bh_schedule_oneshot(ctx, vhost_user_blk_chr_closed_bh, opaque);
-
-            /*
-             * Move vhost device to the stopped state. The vhost-user device
-             * will be clean up and disconnected in BH. This can be useful in
-             * the vhost migration code. If disconnect was caught there is an
-             * option for the general vhost code to get the dev state without
-             * knowing its type (in this case vhost-user).
-             *
-             * FIXME: this is sketchy to be reaching into vhost_dev
-             * now because we are forcing something that implies we
-             * have executed vhost_dev_stop() but that won't happen
-             * until vhost_user_blk_stop() gets called from the bh.
-             * Really this state check should be tracked locally.
-             */
-            s->dev.started = false;
-        }
+        /* defer close until later to avoid circular close */
+        vhost_user_async_close(dev, &s->chardev, &s->dev,
+                               vhost_user_blk_disconnect);
         break;
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
diff --git a/hw/virtio/vhost-user-gpio.c b/hw/virtio/vhost-user-gpio.c
index be9be08b4c..b7b82a1099 100644
--- a/hw/virtio/vhost-user-gpio.c
+++ b/hw/virtio/vhost-user-gpio.c
@@ -233,6 +233,8 @@ static int vu_gpio_connect(DeviceState *dev, Error **errp)
     return 0;
 }
 
+static void vu_gpio_event(void *opaque, QEMUChrEvent event);
+
 static void vu_gpio_disconnect(DeviceState *dev)
 {
     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
@@ -245,6 +247,11 @@ static void vu_gpio_disconnect(DeviceState *dev)
 
     vu_gpio_stop(vdev);
     vhost_dev_cleanup(&gpio->vhost_dev);
+
+    /* Re-instate the event handler for new connections */
+    qemu_chr_fe_set_handlers(&gpio->chardev,
+                             NULL, NULL, vu_gpio_event,
+                             NULL, dev, NULL, true);
 }
 
 static void vu_gpio_event(void *opaque, QEMUChrEvent event)
@@ -262,7 +269,9 @@ static void vu_gpio_event(void *opaque, QEMUChrEvent event)
         }
         break;
     case CHR_EVENT_CLOSED:
-        vu_gpio_disconnect(dev);
+        /* defer close until later to avoid circular close */
+        vhost_user_async_close(dev, &gpio->chardev, &gpio->vhost_dev,
+                               vu_gpio_disconnect);
         break;
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index abe23d4ebe..8f635844af 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -21,6 +21,7 @@
 #include "qemu/error-report.h"
 #include "qemu/main-loop.h"
 #include "qemu/sockets.h"
+#include "sysemu/runstate.h"
 #include "sysemu/cryptodev.h"
 #include "migration/migration.h"
 #include "migration/postcopy-ram.h"
@@ -2670,6 +2671,76 @@ void vhost_user_cleanup(VhostUserState *user)
     user->chr = NULL;
 }
 
+
+typedef struct {
+    vu_async_close_fn cb;
+    DeviceState *dev;
+    CharBackend *cd;
+    struct vhost_dev *vhost;
+} VhostAsyncCallback;
+
+static void vhost_user_async_close_bh(void *opaque)
+{
+    VhostAsyncCallback *data = opaque;
+    struct vhost_dev *vhost = data->vhost;
+
+    /*
+     * If the vhost_dev has been cleared in the meantime there is
+     * nothing left to do as some other path has completed the
+     * cleanup.
+     */
+    if (vhost->vdev) {
+        data->cb(data->dev);
+    }
+
+    g_free(data);
+}
+
+/*
+ * We only schedule the work if the machine is running. If suspended
+ * we want to keep all the in-flight data as is for migration
+ * purposes.
+ */
+void vhost_user_async_close(DeviceState *d,
+                            CharBackend *chardev, struct vhost_dev *vhost,
+                            vu_async_close_fn cb)
+{
+    if (!runstate_check(RUN_STATE_SHUTDOWN)) {
+        /*
+         * A close event may happen during a read/write, but vhost
+         * code assumes the vhost_dev remains setup, so delay the
+         * stop & clear.
+         */
+        AioContext *ctx = qemu_get_current_aio_context();
+        VhostAsyncCallback *data = g_new0(VhostAsyncCallback, 1);
+
+        /* Save data for the callback */
+        data->cb = cb;
+        data->dev = d;
+        data->cd = chardev;
+        data->vhost = vhost;
+
+        /* Disable any further notifications on the chardev */
+        qemu_chr_fe_set_handlers(chardev,
+                                 NULL, NULL, NULL, NULL, NULL, NULL,
+                                 false);
+
+        aio_bh_schedule_oneshot(ctx, vhost_user_async_close_bh, data);
+
+        /*
+         * Move vhost device to the stopped state. The vhost-user device
+         * will be clean up and disconnected in BH. This can be useful in
+         * the vhost migration code. If disconnect was caught there is an
+         * option for the general vhost code to get the dev state without
+         * knowing its type (in this case vhost-user).
+         *
+         * Note if the vhost device is fully cleared by the time we
+         * execute the bottom half we won't continue with the cleanup.
+         */
+        vhost->started = false;
+    }
+}
+
 static int vhost_user_dev_start(struct vhost_dev *dev, bool started)
 {
     if (!virtio_has_feature(dev->protocol_features,
-- 
MST

[PULL 5/5] include/hw: VM state takes precedence in virtio_device_should_start

[Michael S. Tsirkin]

From: Alex Bennée <alex.bennee@linaro.org>

The VM status should always preempt the device status for these
checks. This ensures the device is in the correct state when we
suspend the VM prior to migrations. This restores the checks to the
order they where in before the refactoring moved things around.

While we are at it lets improve our documentation of the various
fields involved and document the two functions.

Fixes: 9f6bcfd99f (hw/virtio: move vm_running check to virtio_device_started)
Fixes: 259d69c00b (hw/virtio: introduce virtio_device_should_start)
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20221130112439.2527228-6-alex.bennee@linaro.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/hw/virtio/virtio.h | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index a973811cbf..acfd4df125 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -116,6 +116,13 @@ struct VirtIODevice
     bool broken; /* device in invalid state, needs reset */
     bool use_disabled_flag; /* allow use of 'disable' flag when needed */
     bool disabled; /* device in temporarily disabled state */
+    /**
+     * @use_started: true if the @started flag should be used to check the
+     * current state of the VirtIO device. Otherwise status bits
+     * should be checked for a current status of the device.
+     * @use_started is only set via QMP and defaults to true for all
+     * modern machines (since 4.1).
+     */
     bool use_started;
     bool started;
     bool start_on_kick; /* when virtio 1.0 feature has not been negotiated */
@@ -391,6 +398,16 @@ static inline bool virtio_is_big_endian(VirtIODevice *vdev)
     return false;
 }
 
+/**
+ * virtio_device_started() - check if device started
+ * @vdev - the VirtIO device
+ * @status - the devices status bits
+ *
+ * Check if the device is started. For most modern machines this is
+ * tracked via the @vdev->started field (to support migration),
+ * otherwise we check for the final negotiated status bit that
+ * indicates everything is ready.
+ */
 static inline bool virtio_device_started(VirtIODevice *vdev, uint8_t status)
 {
     if (vdev->use_started) {
@@ -411,15 +428,11 @@ static inline bool virtio_device_started(VirtIODevice *vdev, uint8_t status)
  */
 static inline bool virtio_device_should_start(VirtIODevice *vdev, uint8_t status)
 {
-    if (vdev->use_started) {
-        return vdev->started;
-    }
-
     if (!vdev->vm_running) {
         return false;
     }
 
-    return status & VIRTIO_CONFIG_S_DRIVER_OK;
+    return virtio_device_started(vdev, status);
 }
 
 static inline void virtio_set_started(VirtIODevice *vdev, bool started)
-- 
MST

[PULL 3/5] hw/virtio: add started_vu status field to vhost-user-gpio

[Michael S. Tsirkin]

From: Alex Bennée <alex.bennee@linaro.org>

As per the fix to vhost-user-blk in f5b22d06fb (vhost: recheck dev
state in the vhost_migration_log routine) we really should track the
connection and starting separately.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20221130112439.2527228-4-alex.bennee@linaro.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/hw/virtio/vhost-user-gpio.h | 10 ++++++++++
 hw/virtio/vhost-user-gpio.c         | 11 ++++-------
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/include/hw/virtio/vhost-user-gpio.h b/include/hw/virtio/vhost-user-gpio.h
index 4fe9aeecc0..a9305c5e6c 100644
--- a/include/hw/virtio/vhost-user-gpio.h
+++ b/include/hw/virtio/vhost-user-gpio.h
@@ -28,7 +28,17 @@ struct VHostUserGPIO {
     VhostUserState vhost_user;
     VirtQueue *command_vq;
     VirtQueue *interrupt_vq;
+    /**
+     * There are at least two steps of initialization of the
+     * vhost-user device. The first is a "connect" step and
+     * second is a "start" step. Make a separation between
+     * those initialization phases by using two fields.
+     *
+     * @connected: see vu_gpio_connect()/vu_gpio_disconnect()
+     * @started_vu: see vu_gpio_start()/vu_gpio_stop()
+     */
     bool connected;
+    bool started_vu;
     /*< public >*/
 };
 
diff --git a/hw/virtio/vhost-user-gpio.c b/hw/virtio/vhost-user-gpio.c
index 0b40ebd15a..be9be08b4c 100644
--- a/hw/virtio/vhost-user-gpio.c
+++ b/hw/virtio/vhost-user-gpio.c
@@ -86,6 +86,7 @@ static int vu_gpio_start(VirtIODevice *vdev)
         error_report("Error starting vhost-user-gpio: %d", ret);
         goto err_guest_notifiers;
     }
+    gpio->started_vu = true;
 
     /*
      * guest_notifier_mask/pending not used yet, so just unmask
@@ -126,16 +127,12 @@ static void vu_gpio_stop(VirtIODevice *vdev)
     struct vhost_dev *vhost_dev = &gpio->vhost_dev;
     int ret;
 
-    if (!k->set_guest_notifiers) {
+    if (!gpio->started_vu) {
         return;
     }
+    gpio->started_vu = false;
 
-    /*
-     * We can call vu_gpio_stop multiple times, for example from
-     * vm_state_notify and the final object finalisation. Check we
-     * aren't already stopped before doing so.
-     */
-    if (!vhost_dev_is_started(vhost_dev)) {
+    if (!k->set_guest_notifiers) {
         return;
     }
 
-- 
MST

Re: [PULL 0/5] virtio: regression fix

[Stefan Hajnoczi]

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Applied, thanks.

Please update the changelog at https://wiki.qemu.org/ChangeLog/7.2 for any user-visible changes.

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