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Re: [PATCH for-9.0 v2] vdpa-dev: Fix initialisation order to restore VDU
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From: |
Stefano Garzarella |
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Subject: |
Re: [PATCH for-9.0 v2] vdpa-dev: Fix initialisation order to restore VDUSE compatibility |
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Date: |
Fri, 15 Mar 2024 16:07:45 +0100 |
On Fri, Mar 15, 2024 at 03:03:31PM +0100, Kevin Wolf wrote:
VDUSE requires that virtqueues are first enabled before the DRIVER_OK
status flag is set; with the current API of the kernel module, it is
impossible to enable the opposite order in our block export code because
userspace is not notified when a virtqueue is enabled.
This requirement also mathces the normal initialisation order as done by
the generic vhost code in QEMU. However, commit 6c482547 accidentally
changed the order for vdpa-dev and broke access to VDUSE devices with
this.
This changes vdpa-dev to use the normal order again and use the standard
vhost callback .vhost_set_vring_enable for this. VDUSE devices can be
used with vdpa-dev again after this fix.
vhost_net intentionally avoided enabling the vrings for vdpa and does
this manually later while it does enable them for other vhost backends.
Reflect this in the vhost_net code and return early for vdpa, so that
the behaviour doesn't change for this device.
Cc: qemu-stable@nongnu.org
Fixes: 6c4825476a4351530bcac17abab72295b75ffe98
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
v2:
- Actually make use of the @enable parameter
- Change vhost_net to preserve the current behaviour
hw/net/vhost_net.c | 10 ++++++++++
hw/virtio/vdpa-dev.c | 5 +----
hw/virtio/vhost-vdpa.c | 27 +++++++++++++++++++++++++--
hw/virtio/vhost.c | 8 +++++++-
4 files changed, 43 insertions(+), 7 deletions(-)
diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index e8e1661646..fd1a93701a 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -541,6 +541,16 @@ int vhost_set_vring_enable(NetClientState *nc, int enable)
VHostNetState *net = get_vhost_net(nc);
const VhostOps *vhost_ops = net->dev.vhost_ops;
+ /*
+ * vhost-vdpa network devices need to enable dataplane virtqueues after
+ * DRIVER_OK, so they can recover device state before starting dataplane.
+ * Because of that, we don't enable virtqueues here and leave it to
+ * net/vhost-vdpa.c.
+ */
+ if (nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) {
+ return 0;
+ }
+
nc->vring_enable = enable;
if (vhost_ops && vhost_ops->vhost_set_vring_enable) {
diff --git a/hw/virtio/vdpa-dev.c b/hw/virtio/vdpa-dev.c
index eb9ecea83b..13e87f06f6 100644
--- a/hw/virtio/vdpa-dev.c
+++ b/hw/virtio/vdpa-dev.c
@@ -253,14 +253,11 @@ static int vhost_vdpa_device_start(VirtIODevice *vdev,
Error **errp)
s->dev.acked_features = vdev->guest_features;
- ret = vhost_dev_start(&s->dev, vdev, false);
+ ret = vhost_dev_start(&s->dev, vdev, true);
if (ret < 0) {
error_setg_errno(errp, -ret, "Error starting vhost");
goto err_guest_notifiers;
}
- for (i = 0; i < s->dev.nvqs; ++i) {
- vhost_vdpa_set_vring_ready(&s->vdpa, i);
- }
s->started = true;
/*
diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index ddae494ca8..401afac2f5 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -886,12 +886,13 @@ static int vhost_vdpa_get_vq_index(struct vhost_dev *dev,
int idx)
return idx;
}
-int vhost_vdpa_set_vring_ready(struct vhost_vdpa *v, unsigned idx)
+static int vhost_vdpa_set_vring_enable_one(struct vhost_vdpa *v, unsigned idx,
+ int enable)
{
struct vhost_dev *dev = v->dev;
struct vhost_vring_state state = {
.index = idx,
- .num = 1,
+ .num = enable,
};
int r = vhost_vdpa_call(dev, VHOST_VDPA_SET_VRING_ENABLE, &state);
After this line we now have:
trace_vhost_vdpa_set_vring_ready(dev, idx, r);
Should we rename it or move it to the new function?
If we rename it, we should trace also `enable`.
@@ -899,6 +900,27 @@ int vhost_vdpa_set_vring_ready(struct vhost_vdpa
*v, unsigned idx)
return r;
}
+static int vhost_vdpa_set_vring_enable(struct vhost_dev *dev, int enable)
+{
+ struct vhost_vdpa *v = dev->opaque;
+ unsigned int i;
+ int ret;
+
+ for (i = 0; i < dev->nvqs; ++i) {
+ ret = vhost_vdpa_set_vring_enable_one(v, i, enable);
+ if (ret < 0) {
+ return ret;
+ }
+ }
+
+ return 0;
+}
+
+int vhost_vdpa_set_vring_ready(struct vhost_vdpa *v, unsigned idx)
+{
+ return vhost_vdpa_set_vring_enable_one(v, idx, 1);
+}
+
static int vhost_vdpa_set_config_call(struct vhost_dev *dev,
int fd)
{
@@ -1514,6 +1536,7 @@ const VhostOps vdpa_ops = {
.vhost_set_features = vhost_vdpa_set_features,
.vhost_reset_device = vhost_vdpa_reset_device,
.vhost_get_vq_index = vhost_vdpa_get_vq_index,
+ .vhost_set_vring_enable = vhost_vdpa_set_vring_enable,
.vhost_get_config = vhost_vdpa_get_config,
.vhost_set_config = vhost_vdpa_set_config,
.vhost_requires_shm_log = NULL,
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 2c9ac79468..decfb85184 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1984,7 +1984,13 @@ static int vhost_dev_set_vring_enable(struct vhost_dev
*hdev, int enable)
return hdev->vhost_ops->vhost_set_vring_enable(hdev, enable);
}
-/* Host notifiers must be enabled at this point. */
+/*
+ * Host notifiers must be enabled at this point.
+ *
+ * If @vring is true, this function will enable all vrings before starting the
Nit: @vrings
+ * device. If it is false, the vring initialization is left to be done by the
+ * caller.
+ */
int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev, bool vrings)
{
int i, r;
--
2.44.0
The rest LGTM, but while reviewing I was thinking whether it would be
better to split the patch into two: first patch to support
.vhost_set_vring_enable() for vhost-vdpa, second patch to fix
hw/virtio/vdpa-dev.c.
But I'm not sure this is a good idea since the second is strictly
dependent on the first.
Thanks,
Stefano