Asias He (2): tcm_vhost: Use vq->private_data to indicate if the endpoint is setup tcm_vhost: Initialize vq->last_used_idx when set endpoint drivers/vhost/tcm_vhost.c | 47 +++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 41 insertions(+), 6 deletions(-) -- 1.8.1.4
Asias He
2013-Mar-22 02:52 UTC
[PATCH 1/2] tcm_vhost: Use vq->private_data to indicate if the endpoint is setup
Currently, vs->vs_endpoint is used indicate if the endpoint is setup or
not. It is set or cleared in vhost_scsi_set_endpoint() or
vhost_scsi_clear_endpoint() under the vs->dev.mutex lock. However, when
we check it in vhost_scsi_handle_vq(), we ignored the lock.
Instead of using the vs->vs_endpoint and the vs->dev.mutex lock to
indicate the status of the endpoint, we use per virtqueue
vq->private_data to indicate it. In this way, we can only take the
vq->mutex lock which is per queue and make the concurrent multiqueue
process having less lock contention. Further, in the read side of
vq->private_data, we can even do not take only lock if it is accessed in
the vhost worker thread, because it is protected by "vhost rcu".
Signed-off-by: Asias He <asias at redhat.com>
---
drivers/vhost/tcm_vhost.c | 46 ++++++++++++++++++++++++++++++++++++++++------
1 file changed, 40 insertions(+), 6 deletions(-)
diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
index 43fb11e..099feef 100644
--- a/drivers/vhost/tcm_vhost.c
+++ b/drivers/vhost/tcm_vhost.c
@@ -67,7 +67,6 @@ struct vhost_scsi {
/* Protected by vhost_scsi->dev.mutex */
struct tcm_vhost_tpg *vs_tpg[VHOST_SCSI_MAX_TARGET];
char vs_vhost_wwpn[TRANSPORT_IQN_LEN];
- bool vs_endpoint;
struct vhost_dev dev;
struct vhost_virtqueue vqs[VHOST_SCSI_MAX_VQ];
@@ -91,6 +90,24 @@ static int iov_num_pages(struct iovec *iov)
((unsigned long)iov->iov_base & PAGE_MASK)) >> PAGE_SHIFT;
}
+static bool tcm_vhost_check_endpoint(struct vhost_virtqueue *vq)
+{
+ bool ret = false;
+
+ /*
+ * We can handle the vq only after the endpoint is setup by calling the
+ * VHOST_SCSI_SET_ENDPOINT ioctl.
+ *
+ * TODO: Check that we are running from vhost_worker which acts
+ * as read-side critical section for vhost kind of RCU.
+ * See the comments in struct vhost_virtqueue in drivers/vhost/vhost.h
+ */
+ if (rcu_dereference_check(vq->private_data, 1))
+ ret = true;
+
+ return ret;
+}
+
static int tcm_vhost_check_true(struct se_portal_group *se_tpg)
{
return 1;
@@ -581,8 +598,7 @@ static void vhost_scsi_handle_vq(struct vhost_scsi *vs,
int head, ret;
u8 target;
- /* Must use ioctl VHOST_SCSI_SET_ENDPOINT */
- if (unlikely(!vs->vs_endpoint))
+ if (!tcm_vhost_check_endpoint(vq))
return;
mutex_lock(&vq->mutex);
@@ -781,8 +797,9 @@ static int vhost_scsi_set_endpoint(
{
struct tcm_vhost_tport *tv_tport;
struct tcm_vhost_tpg *tv_tpg;
+ struct vhost_virtqueue *vq;
bool match = false;
- int index, ret;
+ int index, ret, i;
mutex_lock(&vs->dev.mutex);
/* Verify that ring has been setup correctly. */
@@ -826,7 +843,13 @@ static int vhost_scsi_set_endpoint(
if (match) {
memcpy(vs->vs_vhost_wwpn, t->vhost_wwpn,
sizeof(vs->vs_vhost_wwpn));
- vs->vs_endpoint = true;
+ for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {
+ vq = &vs->vqs[i];
+ /* Flushing the vhost_work acts as synchronize_rcu */
+ mutex_lock(&vq->mutex);
+ rcu_assign_pointer(vq->private_data, vs);
+ mutex_unlock(&vq->mutex);
+ }
ret = 0;
} else {
ret = -EEXIST;
@@ -842,6 +865,8 @@ static int vhost_scsi_clear_endpoint(
{
struct tcm_vhost_tport *tv_tport;
struct tcm_vhost_tpg *tv_tpg;
+ struct vhost_virtqueue *vq;
+ bool match = false;
int index, ret, i;
u8 target;
@@ -877,9 +902,18 @@ static int vhost_scsi_clear_endpoint(
}
tv_tpg->tv_tpg_vhost_count--;
vs->vs_tpg[target] = NULL;
- vs->vs_endpoint = false;
+ match = true;
mutex_unlock(&tv_tpg->tv_tpg_mutex);
}
+ if (match) {
+ for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {
+ vq = &vs->vqs[i];
+ /* Flushing the vhost_work acts as synchronize_rcu */
+ mutex_lock(&vq->mutex);
+ rcu_assign_pointer(vq->private_data, NULL);
+ mutex_unlock(&vq->mutex);
+ }
+ }
mutex_unlock(&vs->dev.mutex);
return 0;
--
1.8.1.4
Asias He
2013-Mar-22 02:52 UTC
[PATCH 2/2] tcm_vhost: Initialize vq->last_used_idx when set endpoint
This patch fixes guest hang when booting seabios and guest. [ 0.576238] scsi0 : Virtio SCSI HBA [ 0.616754] virtio_scsi virtio1: request:id 0 is not a head! vq->last_used_idx is initialized only when /dev/vhost-scsi is opened or closed. vhost_scsi_open -> vhost_dev_init() -> vhost_vq_reset() vhost_scsi_release() -> vhost_dev_cleanup -> vhost_vq_reset() So, when guest talks to tcm_vhost after seabios does, vq->last_used_idx still contains the old valule for seabios. This confuses guest. Fix this by calling vhost_init_used() to init vq->last_used_idx when we set endpoint. Signed-off-by: Asias He <asias at redhat.com> --- drivers/vhost/tcm_vhost.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c index 099feef..0524267 100644 --- a/drivers/vhost/tcm_vhost.c +++ b/drivers/vhost/tcm_vhost.c @@ -848,6 +848,7 @@ static int vhost_scsi_set_endpoint( /* Flushing the vhost_work acts as synchronize_rcu */ mutex_lock(&vq->mutex); rcu_assign_pointer(vq->private_data, vs); + vhost_init_used(vq); mutex_unlock(&vq->mutex); } ret = 0; -- 1.8.1.4
Michael S. Tsirkin
2013-Mar-25 11:15 UTC
[PATCH 1/2] tcm_vhost: Use vq->private_data to indicate if the endpoint is setup
On Fri, Mar 22, 2013 at 10:52:27AM +0800, Asias He wrote:> Currently, vs->vs_endpoint is used indicate if the endpoint is setup or > not. It is set or cleared in vhost_scsi_set_endpoint() or > vhost_scsi_clear_endpoint() under the vs->dev.mutex lock. However, when > we check it in vhost_scsi_handle_vq(), we ignored the lock. > > Instead of using the vs->vs_endpoint and the vs->dev.mutex lock to > indicate the status of the endpoint, we use per virtqueue > vq->private_data to indicate it. In this way, we can only take the > vq->mutex lock which is per queue and make the concurrent multiqueue > process having less lock contention. Further, in the read side of > vq->private_data, we can even do not take only lock if it is accessed in > the vhost worker thread, because it is protected by "vhost rcu". > > Signed-off-by: Asias He <asias at redhat.com>Need to think some more about this, in any case, not 3.9 material IMO.> --- > drivers/vhost/tcm_vhost.c | 46 ++++++++++++++++++++++++++++++++++++++++------ > 1 file changed, 40 insertions(+), 6 deletions(-) > > diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c > index 43fb11e..099feef 100644 > --- a/drivers/vhost/tcm_vhost.c > +++ b/drivers/vhost/tcm_vhost.c > @@ -67,7 +67,6 @@ struct vhost_scsi { > /* Protected by vhost_scsi->dev.mutex */ > struct tcm_vhost_tpg *vs_tpg[VHOST_SCSI_MAX_TARGET]; > char vs_vhost_wwpn[TRANSPORT_IQN_LEN]; > - bool vs_endpoint; > > struct vhost_dev dev; > struct vhost_virtqueue vqs[VHOST_SCSI_MAX_VQ]; > @@ -91,6 +90,24 @@ static int iov_num_pages(struct iovec *iov) > ((unsigned long)iov->iov_base & PAGE_MASK)) >> PAGE_SHIFT; > } > > +static bool tcm_vhost_check_endpoint(struct vhost_virtqueue *vq) > +{ > + bool ret = false; > + > + /* > + * We can handle the vq only after the endpoint is setup by calling the > + * VHOST_SCSI_SET_ENDPOINT ioctl. > + * > + * TODO: Check that we are running from vhost_worker which acts > + * as read-side critical section for vhost kind of RCU. > + * See the comments in struct vhost_virtqueue in drivers/vhost/vhost.h > + */ > + if (rcu_dereference_check(vq->private_data, 1)) > + ret = true; > + > + return ret; > +} > + > static int tcm_vhost_check_true(struct se_portal_group *se_tpg) > { > return 1; > @@ -581,8 +598,7 @@ static void vhost_scsi_handle_vq(struct vhost_scsi *vs, > int head, ret; > u8 target; > > - /* Must use ioctl VHOST_SCSI_SET_ENDPOINT */ > - if (unlikely(!vs->vs_endpoint)) > + if (!tcm_vhost_check_endpoint(vq)) > return; > > mutex_lock(&vq->mutex); > @@ -781,8 +797,9 @@ static int vhost_scsi_set_endpoint( > { > struct tcm_vhost_tport *tv_tport; > struct tcm_vhost_tpg *tv_tpg; > + struct vhost_virtqueue *vq; > bool match = false; > - int index, ret; > + int index, ret, i; > > mutex_lock(&vs->dev.mutex); > /* Verify that ring has been setup correctly. */ > @@ -826,7 +843,13 @@ static int vhost_scsi_set_endpoint( > if (match) { > memcpy(vs->vs_vhost_wwpn, t->vhost_wwpn, > sizeof(vs->vs_vhost_wwpn)); > - vs->vs_endpoint = true; > + for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) { > + vq = &vs->vqs[i]; > + /* Flushing the vhost_work acts as synchronize_rcu */ > + mutex_lock(&vq->mutex); > + rcu_assign_pointer(vq->private_data, vs); > + mutex_unlock(&vq->mutex); > + } > ret = 0; > } else { > ret = -EEXIST; > @@ -842,6 +865,8 @@ static int vhost_scsi_clear_endpoint( > { > struct tcm_vhost_tport *tv_tport; > struct tcm_vhost_tpg *tv_tpg; > + struct vhost_virtqueue *vq; > + bool match = false; > int index, ret, i; > u8 target; > > @@ -877,9 +902,18 @@ static int vhost_scsi_clear_endpoint( > } > tv_tpg->tv_tpg_vhost_count--; > vs->vs_tpg[target] = NULL; > - vs->vs_endpoint = false; > + match = true; > mutex_unlock(&tv_tpg->tv_tpg_mutex); > } > + if (match) { > + for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) { > + vq = &vs->vqs[i]; > + /* Flushing the vhost_work acts as synchronize_rcu */ > + mutex_lock(&vq->mutex); > + rcu_assign_pointer(vq->private_data, NULL); > + mutex_unlock(&vq->mutex); > + } > + } > mutex_unlock(&vs->dev.mutex); > return 0; > > -- > 1.8.1.4
Michael S. Tsirkin
2013-Mar-25 11:16 UTC
[PATCH 2/2] tcm_vhost: Initialize vq->last_used_idx when set endpoint
On Fri, Mar 22, 2013 at 10:52:28AM +0800, Asias He wrote:> This patch fixes guest hang when booting seabios and guest. > > [ 0.576238] scsi0 : Virtio SCSI HBA > [ 0.616754] virtio_scsi virtio1: request:id 0 is not a head! > > vq->last_used_idx is initialized only when /dev/vhost-scsi is > opened or closed. > > vhost_scsi_open -> vhost_dev_init() -> vhost_vq_reset() > vhost_scsi_release() -> vhost_dev_cleanup -> vhost_vq_reset() > > So, when guest talks to tcm_vhost after seabios does, vq->last_used_idx > still contains the old valule for seabios. This confuses guest. > > Fix this by calling vhost_init_used() to init vq->last_used_idx when > we set endpoint. > > Signed-off-by: Asias He <asias at redhat.com>Good catch, thanks. Acked-by: Michael S. Tsirkin <mst at redhat.com> Nicholas can you pick this one up for 3.9 please?> --- > drivers/vhost/tcm_vhost.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c > index 099feef..0524267 100644 > --- a/drivers/vhost/tcm_vhost.c > +++ b/drivers/vhost/tcm_vhost.c > @@ -848,6 +848,7 @@ static int vhost_scsi_set_endpoint( > /* Flushing the vhost_work acts as synchronize_rcu */ > mutex_lock(&vq->mutex); > rcu_assign_pointer(vq->private_data, vs); > + vhost_init_used(vq); > mutex_unlock(&vq->mutex); > } > ret = 0; > -- > 1.8.1.4