[PATCH V3 0/2] tcm_vhost hotplug/hotunplug support

[PATCH V3 0/2] tcm_vhost hotplug/hotunplug support

[Asias He]

Changes in v3:
- Separate the bug fix to another thread

Changes in v2:
- Remove code duplication in tcm_vhost_{hotplug,hotunplug}
- Fix racing of vs_events_nr
- Add flush fix patch to this series


Asias He (2):
  tcm_vhost: Introduce tcm_vhost_check_feature()
  tcm_vhost: Add hotplug/hotunplug support

 drivers/vhost/tcm_vhost.c | 224 ++++++++++++++++++++++++++++++++++++++++++++--
 drivers/vhost/tcm_vhost.h |  10 +++
 2 files changed, 229 insertions(+), 5 deletions(-)

-- 
1.8.1.4

[PATCH V3 1/2] tcm_vhost: Introduce tcm_vhost_check_feature()

[Asias He]

This helper is useful to check if a feature is supported.

Signed-off-by: Asias He <asias@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 drivers/vhost/tcm_vhost.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
index c5157cd..ee6dc47 100644
--- a/drivers/vhost/tcm_vhost.c
+++ b/drivers/vhost/tcm_vhost.c
@@ -91,6 +91,18 @@ static int iov_num_pages(struct iovec *iov)
 	       ((unsigned long)iov->iov_base & PAGE_MASK)) >> PAGE_SHIFT;
 }
 
+static bool tcm_vhost_check_feature(struct vhost_scsi *vs, int feature)
+{
+	bool ret = false;
+
+	mutex_lock(&vs->dev.mutex);
+	if (vhost_has_feature(&vs->dev, feature))
+		ret = true;
+	mutex_unlock(&vs->dev.mutex);
+
+	return ret;
+}
+
 static bool tcm_vhost_check_endpoint(struct vhost_scsi *vs)
 {
 	bool ret = false;
-- 
1.8.1.4

[PATCH V3 2/2] tcm_vhost: Add hotplug/hotunplug support

[Asias He]

In commit 365a7150094 ([SCSI] virtio-scsi: hotplug support for
virtio-scsi), hotplug support is added to virtio-scsi.

This patch adds hotplug and hotunplug support to tcm_vhost.

You can create or delete a LUN in targetcli to hotplug or hotunplug a
LUN in guest.

Signed-off-by: Asias He <asias@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 drivers/vhost/tcm_vhost.c | 212 ++++++++++++++++++++++++++++++++++++++++++++--
 drivers/vhost/tcm_vhost.h |  10 +++
 2 files changed, 217 insertions(+), 5 deletions(-)

diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
index ee6dc47..f80a545 100644
--- a/drivers/vhost/tcm_vhost.c
+++ b/drivers/vhost/tcm_vhost.c
@@ -62,6 +62,9 @@ enum {
 
 #define VHOST_SCSI_MAX_TARGET	256
 #define VHOST_SCSI_MAX_VQ	128
+#define VHOST_SCSI_MAX_EVENT	128
+
+#define VHOST_SCSI_FEATURES (VHOST_FEATURES | (1ULL << VIRTIO_SCSI_F_HOTPLUG))
 
 struct vhost_scsi {
 	/* Protected by vhost_scsi->dev.mutex */
@@ -74,6 +77,13 @@ struct vhost_scsi {
 
 	struct vhost_work vs_completion_work; /* cmd completion work item */
 	struct llist_head vs_completion_list; /* cmd completion queue */
+
+	struct vhost_work vs_event_work; /* evt injection work item */
+	struct llist_head vs_event_list; /* evt injection queue */
+
+	bool vs_events_dropped; /* any missed events, protected by dev.mutex */
+	u64 vs_events_nr; /* # of pennding events, protected by dev.mutex */
+
 };
 
 /* Local pointer to allocated TCM configfs fabric module */
@@ -115,6 +125,16 @@ static bool tcm_vhost_check_endpoint(struct vhost_scsi *vs)
 	return ret;
 }
 
+static bool tcm_vhost_check_events_dropped(struct vhost_scsi *vs)
+{
+	bool ret;
+
+	mutex_lock(&vs->dev.mutex);
+	ret = vs->vs_events_dropped;
+	mutex_unlock(&vs->dev.mutex);
+
+	return ret;
+}
 static int tcm_vhost_check_true(struct se_portal_group *se_tpg)
 {
 	return 1;
@@ -365,6 +385,35 @@ static int tcm_vhost_queue_tm_rsp(struct se_cmd *se_cmd)
 	return 0;
 }
 
+static void tcm_vhost_free_evt(struct vhost_scsi *vs, struct tcm_vhost_evt *evt)
+{
+	mutex_lock(&vs->dev.mutex);
+	vs->vs_events_nr--;
+	kfree(evt);
+	mutex_unlock(&vs->dev.mutex);
+}
+
+static struct tcm_vhost_evt *tcm_vhost_allocate_evt(struct vhost_scsi *vs,
+	u32 event, u32 reason)
+{
+	struct tcm_vhost_evt *evt;
+
+	mutex_lock(&vs->dev.mutex);
+	if (vs->vs_events_nr > VHOST_SCSI_MAX_EVENT) {
+		mutex_unlock(&vs->dev.mutex);
+		return NULL;
+	}
+
+	evt = kzalloc(sizeof(*evt), GFP_KERNEL);
+	if (evt) {
+		evt->event.event = event;
+		evt->event.reason = reason;
+		vs->vs_events_nr++;
+	}
+	mutex_unlock(&vs->dev.mutex);
+	return evt;
+}
+
 static void vhost_scsi_free_cmd(struct tcm_vhost_cmd *tv_cmd)
 {
 	struct se_cmd *se_cmd = &tv_cmd->tvc_se_cmd;
@@ -383,6 +432,77 @@ static void vhost_scsi_free_cmd(struct tcm_vhost_cmd *tv_cmd)
 	kfree(tv_cmd);
 }
 
+static void tcm_vhost_do_evt_work(struct vhost_scsi *vs,
+	struct virtio_scsi_event *event)
+{
+	struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT];
+	struct virtio_scsi_event __user *eventp;
+	unsigned out, in;
+	int head, ret;
+
+	if (!tcm_vhost_check_endpoint(vs))
+		return;
+
+	mutex_lock(&vq->mutex);
+again:
+	vhost_disable_notify(&vs->dev, vq);
+	head = vhost_get_vq_desc(&vs->dev, vq, vq->iov,
+			ARRAY_SIZE(vq->iov), &out, &in,
+			NULL, NULL);
+	if (head < 0) {
+		mutex_lock(&vs->dev.mutex);
+		vs->vs_events_dropped = true;
+		mutex_unlock(&vs->dev.mutex);
+		goto out;
+	}
+	if (head == vq->num) {
+		if (vhost_enable_notify(&vs->dev, vq))
+			goto again;
+		mutex_lock(&vs->dev.mutex);
+		vs->vs_events_dropped = true;
+		mutex_unlock(&vs->dev.mutex);
+		goto out;
+	}
+
+	if ((vq->iov[out].iov_len != sizeof(struct virtio_scsi_event))) {
+		vq_err(vq, "Expecting virtio_scsi_event, got %zu bytes\n",
+				vq->iov[out].iov_len);
+		goto out;
+	}
+
+	mutex_lock(&vs->dev.mutex);
+	if (vs->vs_events_dropped) {
+		event->event |= VIRTIO_SCSI_T_EVENTS_MISSED;
+		vs->vs_events_dropped = false;
+	}
+	mutex_unlock(&vs->dev.mutex);
+
+	eventp = vq->iov[out].iov_base;
+	ret = __copy_to_user(eventp, event, sizeof(*event));
+	if (!ret)
+		vhost_add_used_and_signal(&vs->dev, vq, head, 0);
+	else
+		vq_err(vq, "Faulted on tcm_vhost_send_event\n");
+out:
+	mutex_unlock(&vq->mutex);
+}
+
+static void tcm_vhost_evt_work(struct vhost_work *work)
+{
+	struct vhost_scsi *vs = container_of(work, struct vhost_scsi,
+					vs_event_work);
+	struct tcm_vhost_evt *evt;
+	struct llist_node *llnode;
+
+	llnode = llist_del_all(&vs->vs_event_list);
+	while (llnode) {
+		evt = llist_entry(llnode, struct tcm_vhost_evt, list);
+		llnode = llist_next(llnode);
+		tcm_vhost_do_evt_work(vs, &evt->event);
+		tcm_vhost_free_evt(vs, evt);
+	}
+}
+
 /* Fill in status and signal that we are done processing this command
  *
  * This is scheduled in the vhost work queue so we are called with the owner
@@ -781,9 +901,46 @@ static void vhost_scsi_ctl_handle_kick(struct vhost_work *work)
 	pr_debug("%s: The handling func for control queue.\n", __func__);
 }
 
+static int tcm_vhost_send_evt(struct vhost_scsi *vs, struct tcm_vhost_tpg *tpg,
+	struct se_lun *lun, u32 event, u32 reason)
+{
+	struct tcm_vhost_evt *evt;
+
+	if (!tcm_vhost_check_endpoint(vs))
+		return -EOPNOTSUPP;
+
+	evt = tcm_vhost_allocate_evt(vs, event, reason);
+	if (!evt) {
+		mutex_lock(&vs->dev.mutex);
+		vs->vs_events_dropped = true;
+		mutex_unlock(&vs->dev.mutex);
+		return -ENOMEM;
+	}
+
+	if (tpg && lun) {
+		/* TODO: share lun setup code with virtio-scsi.ko */
+		evt->event.lun[0] = 0x01;
+		evt->event.lun[1] = tpg->tport_tpgt & 0xFF;
+		if (lun->unpacked_lun >= 256)
+			evt->event.lun[2] = lun->unpacked_lun >> 8 | 0x40 ;
+		evt->event.lun[3] = lun->unpacked_lun & 0xFF;
+	}
+
+	llist_add(&evt->list, &vs->vs_event_list);
+	vhost_work_queue(&vs->dev, &vs->vs_event_work);
+
+	return 0;
+}
+
 static void vhost_scsi_evt_handle_kick(struct vhost_work *work)
 {
-	pr_debug("%s: The handling func for event queue.\n", __func__);
+	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
+						poll.work);
+	struct vhost_scsi *vs = container_of(vq->dev, struct vhost_scsi, dev);
+
+	if (tcm_vhost_check_events_dropped(vs))
+		tcm_vhost_send_evt(vs, NULL, NULL, VIRTIO_SCSI_T_NO_EVENT, 0);
+
 }
 
 static void vhost_scsi_handle_kick(struct vhost_work *work)
@@ -839,6 +996,7 @@ static int vhost_scsi_set_endpoint(
 				return -EEXIST;
 			}
 			tv_tpg->tv_tpg_vhost_count++;
+			tv_tpg->vhost_scsi = vs;
 			vs->vs_tpg[tv_tpg->tport_tpgt] = tv_tpg;
 			smp_mb__after_atomic_inc();
 			match = true;
@@ -902,6 +1060,7 @@ static int vhost_scsi_clear_endpoint(
 			goto err;
 		}
 		tv_tpg->tv_tpg_vhost_count--;
+		tv_tpg->vhost_scsi = NULL;
 		vs->vs_tpg[target] = NULL;
 		vs->vs_endpoint = false;
 		mutex_unlock(&tv_tpg->tv_tpg_mutex);
@@ -924,6 +1083,9 @@ static int vhost_scsi_open(struct inode *inode, struct file *f)
 		return -ENOMEM;
 
 	vhost_work_init(&s->vs_completion_work, vhost_scsi_complete_cmd_work);
+	vhost_work_init(&s->vs_event_work, tcm_vhost_evt_work);
+
+	s->vs_events_nr = 0;
 
 	s->vqs[VHOST_SCSI_VQ_CTL].handle_kick = vhost_scsi_ctl_handle_kick;
 	s->vqs[VHOST_SCSI_VQ_EVT].handle_kick = vhost_scsi_evt_handle_kick;
@@ -966,11 +1128,12 @@ static void vhost_scsi_flush(struct vhost_scsi *vs)
 	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)
 		vhost_scsi_flush_vq(vs, i);
 	vhost_work_flush(&vs->dev, &vs->vs_completion_work);
+	vhost_work_flush(&vs->dev, &vs->vs_event_work);
 }
 
 static int vhost_scsi_set_features(struct vhost_scsi *vs, u64 features)
 {
-	if (features & ~VHOST_FEATURES)
+	if (features & ~VHOST_SCSI_FEATURES)
 		return -EOPNOTSUPP;
 
 	mutex_lock(&vs->dev.mutex);
@@ -1016,7 +1179,7 @@ static long vhost_scsi_ioctl(struct file *f, unsigned int ioctl,
 			return -EFAULT;
 		return 0;
 	case VHOST_GET_FEATURES:
-		features = VHOST_FEATURES;
+		features = VHOST_SCSI_FEATURES;
 		if (copy_to_user(featurep, &features, sizeof features))
 			return -EFAULT;
 		return 0;
@@ -1086,6 +1249,42 @@ static char *tcm_vhost_dump_proto_id(struct tcm_vhost_tport *tport)
 	return "Unknown";
 }
 
+static int tcm_vhost_do_plug(struct tcm_vhost_tpg *tpg,
+	struct se_lun *lun, bool plug)
+{
+
+	struct vhost_scsi *vs = tpg->vhost_scsi;
+	u32 reason;
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	vs = tpg->vhost_scsi;
+	mutex_unlock(&tpg->tv_tpg_mutex);
+	if (!vs)
+		return -EOPNOTSUPP;
+
+	if (!tcm_vhost_check_feature(vs, VIRTIO_SCSI_F_HOTPLUG))
+		return -EOPNOTSUPP;
+
+	if (plug)
+		reason = VIRTIO_SCSI_EVT_RESET_RESCAN;
+	else
+		reason = VIRTIO_SCSI_EVT_RESET_REMOVED;
+
+	return tcm_vhost_send_evt(vs, tpg, lun,
+			VIRTIO_SCSI_T_TRANSPORT_RESET,
+			reason);
+}
+
+static int tcm_vhost_hotplug(struct tcm_vhost_tpg *tpg, struct se_lun *lun)
+{
+	return tcm_vhost_do_plug(tpg, lun, true);
+}
+
+static int tcm_vhost_hotunplug(struct tcm_vhost_tpg *tpg, struct se_lun *lun)
+{
+	return tcm_vhost_do_plug(tpg, lun, false);
+}
+
 static int tcm_vhost_port_link(struct se_portal_group *se_tpg,
 	struct se_lun *lun)
 {
@@ -1096,18 +1295,21 @@ static int tcm_vhost_port_link(struct se_portal_group *se_tpg,
 	tv_tpg->tv_tpg_port_count++;
 	mutex_unlock(&tv_tpg->tv_tpg_mutex);
 
+	tcm_vhost_hotplug(tv_tpg, lun);
+
 	return 0;
 }
 
 static void tcm_vhost_port_unlink(struct se_portal_group *se_tpg,
-	struct se_lun *se_lun)
+	struct se_lun *lun)
 {
 	struct tcm_vhost_tpg *tv_tpg = container_of(se_tpg,
 				struct tcm_vhost_tpg, se_tpg);
-
 	mutex_lock(&tv_tpg->tv_tpg_mutex);
 	tv_tpg->tv_tpg_port_count--;
 	mutex_unlock(&tv_tpg->tv_tpg_mutex);
+
+	tcm_vhost_hotunplug(tv_tpg, lun);
 }
 
 static struct se_node_acl *tcm_vhost_make_nodeacl(
diff --git a/drivers/vhost/tcm_vhost.h b/drivers/vhost/tcm_vhost.h
index 1d2ae7a..94e9ee53 100644
--- a/drivers/vhost/tcm_vhost.h
+++ b/drivers/vhost/tcm_vhost.h
@@ -53,6 +53,7 @@ struct tcm_vhost_nacl {
 	struct se_node_acl se_node_acl;
 };
 
+struct vhost_scsi;
 struct tcm_vhost_tpg {
 	/* Vhost port target portal group tag for TCM */
 	u16 tport_tpgt;
@@ -70,6 +71,8 @@ struct tcm_vhost_tpg {
 	struct tcm_vhost_tport *tport;
 	/* Returned by tcm_vhost_make_tpg() */
 	struct se_portal_group se_tpg;
+	/* Pointer back to struct vhost_scsi, protected by tv_tpg_mutex */
+	struct vhost_scsi *vhost_scsi;
 };
 
 struct tcm_vhost_tport {
@@ -83,6 +86,13 @@ struct tcm_vhost_tport {
 	struct se_wwn tport_wwn;
 };
 
+struct tcm_vhost_evt {
+	/* virtio_scsi event */
+	struct virtio_scsi_event event;
+	/* virtio_scsi event list, serviced from vhost worker thread */
+	struct llist_node list;
+};
+
 /*
  * As per request from MST, keep TCM_VHOST related ioctl defines out of
  * linux/vhost.h (user-space) for now..
-- 
1.8.1.4

Re: [PATCH V3 0/2] tcm_vhost hotplug/hotunplug support

[Nicholas A. Bellinger]

On Tue, 2013-03-12 at 10:45 +0800, Asias He wrote:
> Changes in v3:
> - Separate the bug fix to another thread
> 
> Changes in v2:
> - Remove code duplication in tcm_vhost_{hotplug,hotunplug}
> - Fix racing of vs_events_nr
> - Add flush fix patch to this series
> 
> 
> Asias He (2):
>   tcm_vhost: Introduce tcm_vhost_check_feature()
>   tcm_vhost: Add hotplug/hotunplug support
> 
>  drivers/vhost/tcm_vhost.c | 224 ++++++++++++++++++++++++++++++++++++++++++++--
>  drivers/vhost/tcm_vhost.h |  10 +++
>  2 files changed, 229 insertions(+), 5 deletions(-)
> 

MST, are you OK with these two being applied to target-pending/for-next
now..?

--nab

Re: [PATCH V3 0/2] tcm_vhost hotplug/hotunplug support

[Michael S. Tsirkin]

On Mon, Mar 18, 2013 at 02:46:12PM -0700, Nicholas A. Bellinger wrote:
> On Tue, 2013-03-12 at 10:45 +0800, Asias He wrote:
> > Changes in v3:
> > - Separate the bug fix to another thread
> > 
> > Changes in v2:
> > - Remove code duplication in tcm_vhost_{hotplug,hotunplug}
> > - Fix racing of vs_events_nr
> > - Add flush fix patch to this series
> > 
> > 
> > Asias He (2):
> >   tcm_vhost: Introduce tcm_vhost_check_feature()
> >   tcm_vhost: Add hotplug/hotunplug support
> > 
> >  drivers/vhost/tcm_vhost.c | 224 ++++++++++++++++++++++++++++++++++++++++++++--
> >  drivers/vhost/tcm_vhost.h |  10 +++
> >  2 files changed, 229 insertions(+), 5 deletions(-)
> > 
> 
> MST, are you OK with these two being applied to target-pending/for-next
> now..?
> 
> --nab

Sorry, no, I'd prefer we get userspace support in qemu in first.
If there's only a single user for this driver (kvmtool),
then it was a mistake to merge it, the right thing would be to freeze it
and look at whether we can drop it completely.

I really don't want this, I hope it will be merged and all will
be shiny, but I think it's wrong to rush in more code,
we have some time before the next merge window.

-- 
MST

Re: [PATCH V3 0/2] tcm_vhost hotplug/hotunplug support

[Nicholas A. Bellinger]

On Mon, 2013-03-18 at 23:53 +0200, Michael S. Tsirkin wrote:
> On Mon, Mar 18, 2013 at 02:46:12PM -0700, Nicholas A. Bellinger wrote:
> > On Tue, 2013-03-12 at 10:45 +0800, Asias He wrote:
> > > Changes in v3:
> > > - Separate the bug fix to another thread
> > > 
> > > Changes in v2:
> > > - Remove code duplication in tcm_vhost_{hotplug,hotunplug}
> > > - Fix racing of vs_events_nr
> > > - Add flush fix patch to this series
> > > 
> > > 
> > > Asias He (2):
> > >   tcm_vhost: Introduce tcm_vhost_check_feature()
> > >   tcm_vhost: Add hotplug/hotunplug support
> > > 
> > >  drivers/vhost/tcm_vhost.c | 224 ++++++++++++++++++++++++++++++++++++++++++++--
> > >  drivers/vhost/tcm_vhost.h |  10 +++
> > >  2 files changed, 229 insertions(+), 5 deletions(-)
> > > 
> > 
> > MST, are you OK with these two being applied to target-pending/for-next
> > now..?
> > 
> > --nab
> 
> Sorry, no, I'd prefer we get userspace support in qemu in first.
> If there's only a single user for this driver (kvmtool),
> then it was a mistake to merge it, the right thing would be to freeze it
> and look at whether we can drop it completely.
> 
> I really don't want this, I hope it will be merged and all will
> be shiny, but I think it's wrong to rush in more code,
> we have some time before the next merge window.
> 

Fair enough.

With the seabios issues now out of the way, the proposed vhost-scsi-pci
series from Paolo can make it's way into upstream QEMU in an expedited
fashion.

If Asias is OK with it, I'll take ownership of the WIP code and make
sure it finally makes it into upstream QEMU proper.

Thanks,

--nab

Re: [PATCH V3 0/2] tcm_vhost hotplug/hotunplug support

[Asias He]

On Mon, Mar 18, 2013 at 03:19:30PM -0700, Nicholas A. Bellinger wrote:
> On Mon, 2013-03-18 at 23:53 +0200, Michael S. Tsirkin wrote:
> > On Mon, Mar 18, 2013 at 02:46:12PM -0700, Nicholas A. Bellinger wrote:
> > > On Tue, 2013-03-12 at 10:45 +0800, Asias He wrote:
> > > > Changes in v3:
> > > > - Separate the bug fix to another thread
> > > > 
> > > > Changes in v2:
> > > > - Remove code duplication in tcm_vhost_{hotplug,hotunplug}
> > > > - Fix racing of vs_events_nr
> > > > - Add flush fix patch to this series
> > > > 
> > > > 
> > > > Asias He (2):
> > > >   tcm_vhost: Introduce tcm_vhost_check_feature()
> > > >   tcm_vhost: Add hotplug/hotunplug support
> > > > 
> > > >  drivers/vhost/tcm_vhost.c | 224 ++++++++++++++++++++++++++++++++++++++++++++--
> > > >  drivers/vhost/tcm_vhost.h |  10 +++
> > > >  2 files changed, 229 insertions(+), 5 deletions(-)
> > > > 
> > > 
> > > MST, are you OK with these two being applied to target-pending/for-next
> > > now..?
> > > 
> > > --nab
> > 
> > Sorry, no, I'd prefer we get userspace support in qemu in first.
> > If there's only a single user for this driver (kvmtool),
> > then it was a mistake to merge it, the right thing would be to freeze it
> > and look at whether we can drop it completely.
> > 
> > I really don't want this, I hope it will be merged and all will
> > be shiny, but I think it's wrong to rush in more code,
> > we have some time before the next merge window.
> > 
> 
> Fair enough.
> 
> With the seabios issues now out of the way, the proposed vhost-scsi-pci
> series from Paolo can make it's way into upstream QEMU in an expedited
> fashion.
> 
> If Asias is OK with it, I'll take ownership of the WIP code and make
> sure it finally makes it into upstream QEMU proper.

Nicholas, sure, go ahead. I will send out WIP v3 where you can start
with.

-- 
Asias

Re: [PATCH V3 0/2] tcm_vhost hotplug/hotunplug support

[Paolo Bonzini]

Il 18/03/2013 22:53, Michael S. Tsirkin ha scritto:
> Sorry, no, I'd prefer we get userspace support in qemu in first.
> If there's only a single user for this driver (kvmtool),
> then it was a mistake to merge it, the right thing would be to freeze it
> and look at whether we can drop it completely.

I'm still not sure why this matters for this patch, since it does not
change the userspace ABI.

Paolo

> I really don't want this, I hope it will be merged and all will
> be shiny, but I think it's wrong to rush in more code,
> we have some time before the next merge window.

Re: [PATCH V3 0/2] tcm_vhost hotplug/hotunplug support

[Michael S. Tsirkin]

On Tue, Mar 19, 2013 at 10:36:42AM +0100, Paolo Bonzini wrote:
> Il 18/03/2013 22:53, Michael S. Tsirkin ha scritto:
> > Sorry, no, I'd prefer we get userspace support in qemu in first.
> > If there's only a single user for this driver (kvmtool),
> > then it was a mistake to merge it, the right thing would be to freeze it
> > and look at whether we can drop it completely.
> 
> I'm still not sure why this matters for this patch, since it does not
> change the userspace ABI.
> 
> Paolo

It enables a new feature bit.

> > I really don't want this, I hope it will be merged and all will
> > be shiny, but I think it's wrong to rush in more code,
> > we have some time before the next merge window.

Re: [PATCH V3 0/2] tcm_vhost hotplug/hotunplug support

[Paolo Bonzini]

Il 19/03/2013 14:45, Michael S. Tsirkin ha scritto:
> On Tue, Mar 19, 2013 at 10:36:42AM +0100, Paolo Bonzini wrote:
>> Il 18/03/2013 22:53, Michael S. Tsirkin ha scritto:
>>> Sorry, no, I'd prefer we get userspace support in qemu in first.
>>> If there's only a single user for this driver (kvmtool),
>>> then it was a mistake to merge it, the right thing would be to freeze it
>>> and look at whether we can drop it completely.
>>
>> I'm still not sure why this matters for this patch, since it does not
>> change the userspace ABI.
> 
> It enables a new feature bit.

How does that matter if userspace is not supposed to do anything special
with that bit?

Paolo

>>> I really don't want this, I hope it will be merged and all will
>>> be shiny, but I think it's wrong to rush in more code,
>>> we have some time before the next merge window.