diff mbox series

[v2,3/3] vdpa/mlx5: defer clear_virtqueues to until DRIVER_OK

Message ID 1612993680-29454-4-git-send-email-si-wei.liu@oracle.com (mailing list archive)
State Awaiting Upstream
Headers show
Series mlx5_vdpa bug fixes | expand

Checks

Context Check Description
netdev/tree_selection success Not a local patch

Commit Message

Si-Wei Liu Feb. 10, 2021, 9:48 p.m. UTC 
While virtq is stopped,  get_vq_state() is supposed to
be  called to  get  sync'ed  with  the latest internal
avail_index from device. The saved avail_index is used
to restate  the virtq  once device is started.  Commit
b35ccebe3ef7 introduced the clear_virtqueues() routine
to  reset  the saved  avail_index,  however, the index
gets cleared a bit earlier before get_vq_state() tries
to read it. This would cause consistency problems when
virtq is restarted, e.g. through a series of link down
and link up events. We  could  defer  the  clearing of
avail_index  to  until  the  device  is to be started,
i.e. until  VIRTIO_CONFIG_S_DRIVER_OK  is set again in
set_status().

Fixes: b35ccebe3ef7 ("vdpa/mlx5: Restore the hardware used index after change map")
Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
Acked-by: Jason Wang <jasowang@redhat.com>
---
 drivers/vdpa/mlx5/net/mlx5_vnet.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Eli Cohen Feb. 11, 2021, 7:33 a.m. UTC | #1 
On Wed, Feb 10, 2021 at 01:48:00PM -0800, Si-Wei Liu wrote:
> While virtq is stopped,  get_vq_state() is supposed to
> be  called to  get  sync'ed  with  the latest internal
> avail_index from device. The saved avail_index is used
> to restate  the virtq  once device is started.  Commit
> b35ccebe3ef7 introduced the clear_virtqueues() routine
> to  reset  the saved  avail_index,  however, the index
> gets cleared a bit earlier before get_vq_state() tries
> to read it. This would cause consistency problems when
> virtq is restarted, e.g. through a series of link down
> and link up events. We  could  defer  the  clearing of
> avail_index  to  until  the  device  is to be started,
> i.e. until  VIRTIO_CONFIG_S_DRIVER_OK  is set again in
> set_status().
> 
> Fixes: b35ccebe3ef7 ("vdpa/mlx5: Restore the hardware used index after change map")
> Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
> Acked-by: Jason Wang <jasowang@redhat.com>

Acked-by: Eli Cohen <elic@nvidia.com>

> ---
>  drivers/vdpa/mlx5/net/mlx5_vnet.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index 7c1f789..ce6aae8 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -1777,7 +1777,6 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
>  	if (!status) {
>  		mlx5_vdpa_info(mvdev, "performing device reset\n");
>  		teardown_driver(ndev);
> -		clear_virtqueues(ndev);
>  		mlx5_vdpa_destroy_mr(&ndev->mvdev);
>  		ndev->mvdev.status = 0;
>  		++mvdev->generation;
> @@ -1786,6 +1785,7 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
>  
>  	if ((status ^ ndev->mvdev.status) & VIRTIO_CONFIG_S_DRIVER_OK) {
>  		if (status & VIRTIO_CONFIG_S_DRIVER_OK) {
> +			clear_virtqueues(ndev);
>  			err = setup_driver(ndev);
>  			if (err) {
>  				mlx5_vdpa_warn(mvdev, "failed to setup driver\n");
> -- 
> 1.8.3.1
>
Eli Cohen Feb. 16, 2021, 3:21 p.m. UTC | #2 
On Thu, Feb 11, 2021 at 09:33:14AM +0200, Eli Cohen wrote:
> On Wed, Feb 10, 2021 at 01:48:00PM -0800, Si-Wei Liu wrote:
> > While virtq is stopped,  get_vq_state() is supposed to
> > be  called to  get  sync'ed  with  the latest internal
> > avail_index from device. The saved avail_index is used
> > to restate  the virtq  once device is started.  Commit
> > b35ccebe3ef7 introduced the clear_virtqueues() routine
> > to  reset  the saved  avail_index,  however, the index
> > gets cleared a bit earlier before get_vq_state() tries
> > to read it. This would cause consistency problems when
> > virtq is restarted, e.g. through a series of link down
> > and link up events. We  could  defer  the  clearing of
> > avail_index  to  until  the  device  is to be started,
> > i.e. until  VIRTIO_CONFIG_S_DRIVER_OK  is set again in
> > set_status().
> > 
> > Fixes: b35ccebe3ef7 ("vdpa/mlx5: Restore the hardware used index after change map")
> > Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
> > Acked-by: Jason Wang <jasowang@redhat.com>
> 
> Acked-by: Eli Cohen <elic@nvidia.com>
> 

I take it back. I think we don't need to clear the indexes at all. In
case we need to restore indexes we'll get the right values through
set_vq_state(). If we suspend the virtqueue due to VM being suspended,
qemu will query first and will provide the the queried value. In case of
VM reboot, it will provide 0 in set_vq_state().

I am sending a patch that addresses both reboot and suspend.

> > ---
> >  drivers/vdpa/mlx5/net/mlx5_vnet.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > index 7c1f789..ce6aae8 100644
> > --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > @@ -1777,7 +1777,6 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
> >  	if (!status) {
> >  		mlx5_vdpa_info(mvdev, "performing device reset\n");
> >  		teardown_driver(ndev);
> > -		clear_virtqueues(ndev);
> >  		mlx5_vdpa_destroy_mr(&ndev->mvdev);
> >  		ndev->mvdev.status = 0;
> >  		++mvdev->generation;
> > @@ -1786,6 +1785,7 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
> >  
> >  	if ((status ^ ndev->mvdev.status) & VIRTIO_CONFIG_S_DRIVER_OK) {
> >  		if (status & VIRTIO_CONFIG_S_DRIVER_OK) {
> > +			clear_virtqueues(ndev);
> >  			err = setup_driver(ndev);
> >  			if (err) {
> >  				mlx5_vdpa_warn(mvdev, "failed to setup driver\n");
> > -- 
> > 1.8.3.1
> >
Si-Wei Liu Feb. 17, 2021, 9:55 p.m. UTC | #3 
On 2/16/2021 7:21 AM, Eli Cohen wrote:
> On Thu, Feb 11, 2021 at 09:33:14AM +0200, Eli Cohen wrote:
>> On Wed, Feb 10, 2021 at 01:48:00PM -0800, Si-Wei Liu wrote:
>>> While virtq is stopped,  get_vq_state() is supposed to
>>> be  called to  get  sync'ed  with  the latest internal
>>> avail_index from device. The saved avail_index is used
>>> to restate  the virtq  once device is started.  Commit
>>> b35ccebe3ef7 introduced the clear_virtqueues() routine
>>> to  reset  the saved  avail_index,  however, the index
>>> gets cleared a bit earlier before get_vq_state() tries
>>> to read it. This would cause consistency problems when
>>> virtq is restarted, e.g. through a series of link down
>>> and link up events. We  could  defer  the  clearing of
>>> avail_index  to  until  the  device  is to be started,
>>> i.e. until  VIRTIO_CONFIG_S_DRIVER_OK  is set again in
>>> set_status().
>>>
>>> Fixes: b35ccebe3ef7 ("vdpa/mlx5: Restore the hardware used index after change map")
>>> Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
>>> Acked-by: Jason Wang <jasowang@redhat.com>
>> Acked-by: Eli Cohen <elic@nvidia.com>
>>
> I take it back. I think we don't need to clear the indexes at all. In
> case we need to restore indexes we'll get the right values through
> set_vq_state(). If we suspend the virtqueue due to VM being suspended,
> qemu will query first and will provide the the queried value. In case of
> VM reboot, it will provide 0 in set_vq_state().
>
> I am sending a patch that addresses both reboot and suspend.
With set_vq_state() repurposed to restoring used_index I'm fine with 
this approach.

Do I have to repost a v3 of this series while dropping the 3rd patch?

-Siwei
>
>>> ---
>>>   drivers/vdpa/mlx5/net/mlx5_vnet.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
>>> index 7c1f789..ce6aae8 100644
>>> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
>>> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
>>> @@ -1777,7 +1777,6 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
>>>   	if (!status) {
>>>   		mlx5_vdpa_info(mvdev, "performing device reset\n");
>>>   		teardown_driver(ndev);
>>> -		clear_virtqueues(ndev);
>>>   		mlx5_vdpa_destroy_mr(&ndev->mvdev);
>>>   		ndev->mvdev.status = 0;
>>>   		++mvdev->generation;
>>> @@ -1786,6 +1785,7 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
>>>   
>>>   	if ((status ^ ndev->mvdev.status) & VIRTIO_CONFIG_S_DRIVER_OK) {
>>>   		if (status & VIRTIO_CONFIG_S_DRIVER_OK) {
>>> +			clear_virtqueues(ndev);
>>>   			err = setup_driver(ndev);
>>>   			if (err) {
>>>   				mlx5_vdpa_warn(mvdev, "failed to setup driver\n");
>>> -- 
>>> 1.8.3.1
>>>
Jason Wang Feb. 18, 2021, 6:37 a.m. UTC | #4 
On 2021/2/18 上午5:55, Si-Wei Liu wrote:
>
>
> On 2/16/2021 7:21 AM, Eli Cohen wrote:
>> On Thu, Feb 11, 2021 at 09:33:14AM +0200, Eli Cohen wrote:
>>> On Wed, Feb 10, 2021 at 01:48:00PM -0800, Si-Wei Liu wrote:
>>>> While virtq is stopped,  get_vq_state() is supposed to
>>>> be  called to  get  sync'ed  with  the latest internal
>>>> avail_index from device. The saved avail_index is used
>>>> to restate  the virtq  once device is started.  Commit
>>>> b35ccebe3ef7 introduced the clear_virtqueues() routine
>>>> to  reset  the saved  avail_index,  however, the index
>>>> gets cleared a bit earlier before get_vq_state() tries
>>>> to read it. This would cause consistency problems when
>>>> virtq is restarted, e.g. through a series of link down
>>>> and link up events. We  could  defer  the  clearing of
>>>> avail_index  to  until  the  device  is to be started,
>>>> i.e. until  VIRTIO_CONFIG_S_DRIVER_OK  is set again in
>>>> set_status().
>>>>
>>>> Fixes: b35ccebe3ef7 ("vdpa/mlx5: Restore the hardware used index 
>>>> after change map")
>>>> Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
>>>> Acked-by: Jason Wang <jasowang@redhat.com>
>>> Acked-by: Eli Cohen <elic@nvidia.com>
>>>
>> I take it back. I think we don't need to clear the indexes at all. In
>> case we need to restore indexes we'll get the right values through
>> set_vq_state(). If we suspend the virtqueue due to VM being suspended,
>> qemu will query first and will provide the the queried value. In case of
>> VM reboot, it will provide 0 in set_vq_state().
>>
>> I am sending a patch that addresses both reboot and suspend.
> With set_vq_state() repurposed to restoring used_index I'm fine with 
> this approach.
>
> Do I have to repost a v3 of this series while dropping the 3rd patch?
>
> -Siwei 


Yes, please.

Thanks
diff mbox series

Patch

diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index 7c1f789..ce6aae8 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -1777,7 +1777,6 @@  static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
 	if (!status) {
 		mlx5_vdpa_info(mvdev, "performing device reset\n");
 		teardown_driver(ndev);
-		clear_virtqueues(ndev);
 		mlx5_vdpa_destroy_mr(&ndev->mvdev);
 		ndev->mvdev.status = 0;
 		++mvdev->generation;
@@ -1786,6 +1785,7 @@  static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
 
 	if ((status ^ ndev->mvdev.status) & VIRTIO_CONFIG_S_DRIVER_OK) {
 		if (status & VIRTIO_CONFIG_S_DRIVER_OK) {
+			clear_virtqueues(ndev);
 			err = setup_driver(ndev);
 			if (err) {
 				mlx5_vdpa_warn(mvdev, "failed to setup driver\n");