Re: [virtio-dev] Re: [PATCH v1 1/2] virtio-balloon: tweak config_changed implementation
On 01/04/2019 12:42 AM, Michael S. Tsirkin wrote: On Thu, Jan 03, 2019 at 01:31:01PM +0800, Wei Wang wrote: virtio-ccw has deadlock issues with reading config registers inside the interrupt context, so we tweak the virtballoon_changed implementation by moving the config read operations into the related workqueue contexts. Signed-off-by: Wei Wang --- drivers/virtio/virtio_balloon.c | 54 - 1 file changed, 26 insertions(+), 28 deletions(-) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 728ecd1..9a82a11 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -394,33 +394,15 @@ static void virtballoon_changed(struct virtio_device *vdev) { struct virtio_balloon *vb = vdev->priv; unsigned long flags; - s64 diff = towards_target(vb); - - if (diff) { - spin_lock_irqsave(>stop_update_lock, flags); - if (!vb->stop_update) - queue_work(system_freezable_wq, - >update_balloon_size_work); - spin_unlock_irqrestore(>stop_update_lock, flags); - } - if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { - virtio_cread(vdev, struct virtio_balloon_config, -free_page_report_cmd_id, >cmd_id_received); There's one problem with this approach: previously updating the cmd_id_received here would immediately stop the report in send_free_pages. With this approach we are waiting for the wq to schedule, which might be blocked waiting for report to complete. So host can no longer quickly stop the report in progress. A simple work-around would be to set some kind of flag whenever there is a change interrupt, then have send_free_pages test it and re-read cmd_id_received. Needs to be an atomic I guess ... Yes, sounds better..will update the patch. Best, Wei ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
Re: [PATCH v1 1/2] virtio-balloon: tweak config_changed implementation
On Thu, Jan 03, 2019 at 01:31:01PM +0800, Wei Wang wrote: > virtio-ccw has deadlock issues with reading config registers inside the > interrupt context, so we tweak the virtballoon_changed implementation > by moving the config read operations into the related workqueue contexts. > > Signed-off-by: Wei Wang > --- > drivers/virtio/virtio_balloon.c | 54 > - > 1 file changed, 26 insertions(+), 28 deletions(-) > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > index 728ecd1..9a82a11 100644 > --- a/drivers/virtio/virtio_balloon.c > +++ b/drivers/virtio/virtio_balloon.c > @@ -394,33 +394,15 @@ static void virtballoon_changed(struct virtio_device > *vdev) > { > struct virtio_balloon *vb = vdev->priv; > unsigned long flags; > - s64 diff = towards_target(vb); > - > - if (diff) { > - spin_lock_irqsave(>stop_update_lock, flags); > - if (!vb->stop_update) > - queue_work(system_freezable_wq, > ->update_balloon_size_work); > - spin_unlock_irqrestore(>stop_update_lock, flags); > - } > > - if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { > - virtio_cread(vdev, struct virtio_balloon_config, > - free_page_report_cmd_id, >cmd_id_received); There's one problem with this approach: previously updating the cmd_id_received here would immediately stop the report in send_free_pages. With this approach we are waiting for the wq to schedule, which might be blocked waiting for report to complete. So host can no longer quickly stop the report in progress. A simple work-around would be to set some kind of flag whenever there is a change interrupt, then have send_free_pages test it and re-read cmd_id_received. Needs to be an atomic I guess ... > - if (vb->cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) { > - /* Pass ULONG_MAX to give back all the free pages */ > - return_free_pages_to_mm(vb, ULONG_MAX); > - } else if (vb->cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP && > -vb->cmd_id_received != > -virtio32_to_cpu(vdev, vb->cmd_id_active)) { > - spin_lock_irqsave(>stop_update_lock, flags); > - if (!vb->stop_update) { > - queue_work(vb->balloon_wq, > ->report_free_page_work); > - } > - spin_unlock_irqrestore(>stop_update_lock, flags); > - } > + spin_lock_irqsave(>stop_update_lock, flags); > + if (!vb->stop_update) { > + queue_work(system_freezable_wq, > +>update_balloon_size_work); > + if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) > + queue_work(vb->balloon_wq, >report_free_page_work); > } > + spin_unlock_irqrestore(>stop_update_lock, flags); > } > > static void update_balloon_size(struct virtio_balloon *vb) > @@ -637,11 +619,9 @@ static int send_free_pages(struct virtio_balloon *vb) > return 0; > } > > -static void report_free_page_func(struct work_struct *work) > +static void virtio_balloon_report_free_page(struct virtio_balloon *vb) > { > int err; > - struct virtio_balloon *vb = container_of(work, struct virtio_balloon, > - report_free_page_work); > struct device *dev = >vdev->dev; > > /* Start by sending the received cmd id to host with an outbuf. */ > @@ -659,6 +639,24 @@ static void report_free_page_func(struct work_struct > *work) > dev_err(dev, "Failed to send a stop id, err = %d\n", err); > } > > +static void report_free_page_func(struct work_struct *work) > +{ > + struct virtio_balloon *vb = container_of(work, struct virtio_balloon, > + report_free_page_work); > + > + virtio_cread(vb->vdev, struct virtio_balloon_config, > + free_page_report_cmd_id, >cmd_id_received); > + > + if (vb->cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) { > + /* Pass ULONG_MAX to give back all the free pages */ > + return_free_pages_to_mm(vb, ULONG_MAX); > + } else if (vb->cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP && > +vb->cmd_id_received != > +virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) { > + virtio_balloon_report_free_page(vb); > + } > +} > + > #ifdef CONFIG_BALLOON_COMPACTION > /* > * virtballoon_migratepage - perform the balloon page migration on behalf of > -- > 2.7.4 ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
Re: [PATCH v1 1/2] virtio-balloon: tweak config_changed implementation
On 01/03/2019 05:40 PM, Cornelia Huck wrote: On Thu, 3 Jan 2019 13:31:01 +0800 Wei Wang wrote: virtio-ccw has deadlock issues with reading config registers inside the s/config registers/the config space/ ? Sounds good. interrupt context, so we tweak the virtballoon_changed implementation by moving the config read operations into the related workqueue contexts. Also credit Christian with a Reported-by:? Yes, definitely. Sorry for missing that. Best, Wei ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
Re: [PATCH v1 1/2] virtio-balloon: tweak config_changed implementation
On Thu, 3 Jan 2019 13:31:01 +0800 Wei Wang wrote: > virtio-ccw has deadlock issues with reading config registers inside the s/config registers/the config space/ ? > interrupt context, so we tweak the virtballoon_changed implementation > by moving the config read operations into the related workqueue contexts. Also credit Christian with a Reported-by:? > > Signed-off-by: Wei Wang > --- > drivers/virtio/virtio_balloon.c | 54 > - > 1 file changed, 26 insertions(+), 28 deletions(-) Reviewed-by: Cornelia Huck ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
[PATCH v1 1/2] virtio-balloon: tweak config_changed implementation
virtio-ccw has deadlock issues with reading config registers inside the interrupt context, so we tweak the virtballoon_changed implementation by moving the config read operations into the related workqueue contexts. Signed-off-by: Wei Wang --- drivers/virtio/virtio_balloon.c | 54 - 1 file changed, 26 insertions(+), 28 deletions(-) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 728ecd1..9a82a11 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -394,33 +394,15 @@ static void virtballoon_changed(struct virtio_device *vdev) { struct virtio_balloon *vb = vdev->priv; unsigned long flags; - s64 diff = towards_target(vb); - - if (diff) { - spin_lock_irqsave(>stop_update_lock, flags); - if (!vb->stop_update) - queue_work(system_freezable_wq, - >update_balloon_size_work); - spin_unlock_irqrestore(>stop_update_lock, flags); - } - if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { - virtio_cread(vdev, struct virtio_balloon_config, -free_page_report_cmd_id, >cmd_id_received); - if (vb->cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) { - /* Pass ULONG_MAX to give back all the free pages */ - return_free_pages_to_mm(vb, ULONG_MAX); - } else if (vb->cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP && - vb->cmd_id_received != - virtio32_to_cpu(vdev, vb->cmd_id_active)) { - spin_lock_irqsave(>stop_update_lock, flags); - if (!vb->stop_update) { - queue_work(vb->balloon_wq, - >report_free_page_work); - } - spin_unlock_irqrestore(>stop_update_lock, flags); - } + spin_lock_irqsave(>stop_update_lock, flags); + if (!vb->stop_update) { + queue_work(system_freezable_wq, + >update_balloon_size_work); + if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) + queue_work(vb->balloon_wq, >report_free_page_work); } + spin_unlock_irqrestore(>stop_update_lock, flags); } static void update_balloon_size(struct virtio_balloon *vb) @@ -637,11 +619,9 @@ static int send_free_pages(struct virtio_balloon *vb) return 0; } -static void report_free_page_func(struct work_struct *work) +static void virtio_balloon_report_free_page(struct virtio_balloon *vb) { int err; - struct virtio_balloon *vb = container_of(work, struct virtio_balloon, -report_free_page_work); struct device *dev = >vdev->dev; /* Start by sending the received cmd id to host with an outbuf. */ @@ -659,6 +639,24 @@ static void report_free_page_func(struct work_struct *work) dev_err(dev, "Failed to send a stop id, err = %d\n", err); } +static void report_free_page_func(struct work_struct *work) +{ + struct virtio_balloon *vb = container_of(work, struct virtio_balloon, +report_free_page_work); + + virtio_cread(vb->vdev, struct virtio_balloon_config, +free_page_report_cmd_id, >cmd_id_received); + + if (vb->cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) { + /* Pass ULONG_MAX to give back all the free pages */ + return_free_pages_to_mm(vb, ULONG_MAX); + } else if (vb->cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP && + vb->cmd_id_received != + virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) { + virtio_balloon_report_free_page(vb); + } +} + #ifdef CONFIG_BALLOON_COMPACTION /* * virtballoon_migratepage - perform the balloon page migration on behalf of -- 2.7.4 ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization