Re: [PATCH v7 0/4] Implement vdpasim suspend operation

Re: [PATCH v7 0/4] Implement vdpasim suspend operation

[Michael S. Tsirkin]

On Wed, Aug 10, 2022 at 07:15:08PM +0200, Eugenio Pérez wrote:
> Implement suspend operation for vdpa_sim devices, so vhost-vdpa will offer
> that backend feature and userspace can effectively suspend the device.
> 
> This is a must before getting virtqueue indexes (base) for live migration,
> since the device could modify them after userland gets them. There are
> individual ways to perform that action for some devices
> (VHOST_NET_SET_BACKEND, VHOST_VSOCK_SET_RUNNING, ...) but there was no
> way to perform it for any vhost device (and, in particular, vhost-vdpa).
> 
> After a successful return of ioctl the device must not process more virtqueue
> descriptors. The device can answer to read or writes of config fields as if it
> were not suspended. In particular, writing to "queue_enable" with a value of 1
> will not make the device start processing virtqueue buffers.
> 
> In the future, we will provide features similar to
> VHOST_USER_GET_INFLIGHT_FD so the device can save pending operations.
> 
> Applied on top of [1] branch after removing the old commits.

Except, I can't really do this without invaliding all testing.
Can't you post an incremental patch?

> Comments are welcome.
> 
> v7:
> * Remove ioctl leftover argument and update doc accordingly.

> v6:
> * Remove the resume operation, making the ioctl simpler. We can always add
>   another ioctl for VM_STOP/VM_RESUME operation later.
> * s/stop/suspend/ to differentiate more from reset.
> * Clarify scope of the suspend operation.
> 
> v5:
> * s/not stop/resume/ in doc.
> 
> v4:
> * Replace VHOST_STOP to VHOST_VDPA_STOP in vhost ioctl switch case too.
> 
> v3:
> * s/VHOST_STOP/VHOST_VDPA_STOP/
> * Add documentation and requirements of the ioctl above its definition.
> 
> v2:
> * Replace raw _F_STOP with BIT_ULL(_F_STOP).
> * Fix obtaining of stop ioctl arg (it was not obtained but written).
> * Add stop to vdpa_sim_blk.
> 
> [1] git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git
> 
> Eugenio Pérez (4):
>   vdpa: Add suspend operation
>   vhost-vdpa: introduce SUSPEND backend feature bit
>   vhost-vdpa: uAPI to suspend the device
>   vdpa_sim: Implement suspend vdpa op
> 
>  drivers/vdpa/vdpa_sim/vdpa_sim.c     | 14 +++++++++++
>  drivers/vdpa/vdpa_sim/vdpa_sim.h     |  1 +
>  drivers/vdpa/vdpa_sim/vdpa_sim_blk.c |  3 +++
>  drivers/vdpa/vdpa_sim/vdpa_sim_net.c |  3 +++
>  drivers/vhost/vdpa.c                 | 35 +++++++++++++++++++++++++++-
>  include/linux/vdpa.h                 |  4 ++++
>  include/uapi/linux/vhost.h           |  9 +++++++
>  include/uapi/linux/vhost_types.h     |  2 ++
>  8 files changed, 70 insertions(+), 1 deletion(-)
> 
> -- 
> 2.31.1
> 

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Re: [PATCH v7 1/4] vdpa: Add suspend operation

[Michael S. Tsirkin]

On Wed, Aug 10, 2022 at 07:15:09PM +0200, Eugenio Pérez wrote:
> This operation is optional: It it's not implemented, backend feature bit
> will not be exposed.
> 
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> Message-Id: <20220623160738.632852-2-eperezma@redhat.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

What is this message id doing here?

> ---
>  include/linux/vdpa.h | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
> index 7b4a13d3bd91..d282f464d2f1 100644
> --- a/include/linux/vdpa.h
> +++ b/include/linux/vdpa.h
> @@ -218,6 +218,9 @@ struct vdpa_map_file {
>   * @reset:			Reset device
>   *				@vdev: vdpa device
>   *				Returns integer: success (0) or error (< 0)
> + * @suspend:			Suspend or resume the device (optional)
> + *				@vdev: vdpa device
> + *				Returns integer: success (0) or error (< 0)
>   * @get_config_size:		Get the size of the configuration space includes
>   *				fields that are conditional on feature bits.
>   *				@vdev: vdpa device
> @@ -319,6 +322,7 @@ struct vdpa_config_ops {
>  	u8 (*get_status)(struct vdpa_device *vdev);
>  	void (*set_status)(struct vdpa_device *vdev, u8 status);
>  	int (*reset)(struct vdpa_device *vdev);
> +	int (*suspend)(struct vdpa_device *vdev);
>  	size_t (*get_config_size)(struct vdpa_device *vdev);
>  	void (*get_config)(struct vdpa_device *vdev, unsigned int offset,
>  			   void *buf, unsigned int len);
> -- 
> 2.31.1

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Re: [PATCH v7 1/4] vdpa: Add suspend operation

[Dan Carpenter]

On Thu, Aug 11, 2022 at 04:27:32AM -0400, Michael S. Tsirkin wrote:
> On Wed, Aug 10, 2022 at 07:15:09PM +0200, Eugenio Pérez wrote:
> > This operation is optional: It it's not implemented, backend feature bit
> > will not be exposed.
> > 
> > Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> > Message-Id: <20220623160738.632852-2-eperezma@redhat.com>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> 
> What is this message id doing here?
> 

I like the Message-Id tag.  It means you can `b4 mbox <mesg-id>` and get
the thread.

Linus has complained (rough remembering) that everyone is using the
Link: tag for links to the patch itself.  It's supposed to be for Links
to bugzilla or to the spec or whatever.  Extra information, too much to
put in the commit message.  Now the Link tag is useless because it either
points to the patch or to a bugzilla.  Depend on what you want it to do,
it *always* points to the opposite thing.

But I can't remember what people settled on as the alternative to use
to link to lore...

In theory, we should be able to figure out the link to lore automatically
and there have been a couple projects which tried to do this but they
can't make it work 100%.  Maintainers massage and reformat the patches
too much before applying them.

regards,
dan carpenter

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Re: [PATCH v7 1/4] vdpa: Add suspend operation

[Michael S. Tsirkin]

On Thu, Aug 11, 2022 at 01:15:08PM +0300, Dan Carpenter wrote:
> On Thu, Aug 11, 2022 at 04:27:32AM -0400, Michael S. Tsirkin wrote:
> > On Wed, Aug 10, 2022 at 07:15:09PM +0200, Eugenio Pérez wrote:
> > > This operation is optional: It it's not implemented, backend feature bit
> > > will not be exposed.
> > > 
> > > Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> > > Message-Id: <20220623160738.632852-2-eperezma@redhat.com>
> > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > 
> > What is this message id doing here?
> > 
> 
> I like the Message-Id tag.  It means you can `b4 mbox <mesg-id>` and get
> the thread.

Yes it makes sense in git. But I don't see what it does in this patch
posted to the list. It seems to refer to the previous version of the
patch here. Which is ok I guess but better called out e.g.

Previous-version: <20220623160738.632852-2-eperezma@redhat.com>


> Linus has complained (rough remembering) that everyone is using the
> Link: tag for links to the patch itself.  It's supposed to be for Links
> to bugzilla or to the spec or whatever.  Extra information, too much to
> put in the commit message.  Now the Link tag is useless because it either
> points to the patch or to a bugzilla.  Depend on what you want it to do,
> it *always* points to the opposite thing.
> 
> But I can't remember what people settled on as the alternative to use
> to link to lore...
> 
> In theory, we should be able to figure out the link to lore automatically
> and there have been a couple projects which tried to do this but they
> can't make it work 100%.  Maintainers massage and reformat the patches
> too much before applying them.
> 
> regards,
> dan carpenter

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Re: [PATCH v7 1/4] vdpa: Add suspend operation

[Dan Carpenter]

On Thu, Aug 11, 2022 at 07:23:44AM -0400, Michael S. Tsirkin wrote:
> On Thu, Aug 11, 2022 at 01:15:08PM +0300, Dan Carpenter wrote:
> > On Thu, Aug 11, 2022 at 04:27:32AM -0400, Michael S. Tsirkin wrote:
> > > On Wed, Aug 10, 2022 at 07:15:09PM +0200, Eugenio Pérez wrote:
> > > > This operation is optional: It it's not implemented, backend feature bit
> > > > will not be exposed.
> > > > 
> > > > Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> > > > Message-Id: <20220623160738.632852-2-eperezma@redhat.com>
> > > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > > 
> > > What is this message id doing here?
> > > 
> > 
> > I like the Message-Id tag.  It means you can `b4 mbox <mesg-id>` and get
> > the thread.
> 
> Yes it makes sense in git. But I don't see what it does in this patch
> posted to the list.

Ah.  Okay.  I misunderstood.

> It seems to refer to the previous version of the
> patch here. Which is ok I guess but better called out e.g.
> 
> Previous-version: <20220623160738.632852-2-eperezma@redhat.com>
> 

Let's not go over board with storing previous threads.  That seems like
a headache...

regards,
dan carpenter

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Re: [PATCH v7 3/4] vhost-vdpa: uAPI to suspend the device

[Michael S. Tsirkin]

On Wed, Aug 10, 2022 at 07:15:11PM +0200, Eugenio Pérez wrote:
> The ioctl adds support for suspending the device from userspace.
> 
> This is a must before getting virtqueue indexes (base) for live migration,
> since the device could modify them after userland gets them. There are
> individual ways to perform that action for some devices
> (VHOST_NET_SET_BACKEND, VHOST_VSOCK_SET_RUNNING, ...) but there was no
> way to perform it for any vhost device (and, in particular, vhost-vdpa).
> 
> After a successful return of the ioctl call the device must not process
> more virtqueue descriptors. The device can answer to read or writes of
> config fields as if it were not suspended. In particular, writing to
> "queue_enable" with a value of 1 will not make the device start
> processing buffers of the virtqueue.
> 
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> Message-Id: <20220623160738.632852-4-eperezma@redhat.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

You are not supposed to include upstream maintainer's signoff
like this.

> ---
> v7: Delete argument to ioctl, unused
> ---
>  drivers/vhost/vdpa.c       | 19 +++++++++++++++++++
>  include/uapi/linux/vhost.h |  9 +++++++++
>  2 files changed, 28 insertions(+)
> 
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 3d636e192061..7fa671ac4bdf 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -478,6 +478,22 @@ static long vhost_vdpa_get_vqs_count(struct vhost_vdpa *v, u32 __user *argp)
>  	return 0;
>  }
>  
> +/* After a successful return of ioctl the device must not process more
> + * virtqueue descriptors. The device can answer to read or writes of config
> + * fields as if it were not suspended. In particular, writing to "queue_enable"
> + * with a value of 1 will not make the device start processing buffers.
> + */
> +static long vhost_vdpa_suspend(struct vhost_vdpa *v)
> +{
> +	struct vdpa_device *vdpa = v->vdpa;
> +	const struct vdpa_config_ops *ops = vdpa->config;
> +
> +	if (!ops->suspend)
> +		return -EOPNOTSUPP;
> +
> +	return ops->suspend(vdpa);
> +}
> +
>  static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
>  				   void __user *argp)
>  {
> @@ -654,6 +670,9 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
>  	case VHOST_VDPA_GET_VQS_COUNT:
>  		r = vhost_vdpa_get_vqs_count(v, argp);
>  		break;
> +	case VHOST_VDPA_SUSPEND:
> +		r = vhost_vdpa_suspend(v);
> +		break;
>  	default:
>  		r = vhost_dev_ioctl(&v->vdev, cmd, argp);
>  		if (r == -ENOIOCTLCMD)
> diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
> index cab645d4a645..f9f115a7c75b 100644
> --- a/include/uapi/linux/vhost.h
> +++ b/include/uapi/linux/vhost.h
> @@ -171,4 +171,13 @@
>  #define VHOST_VDPA_SET_GROUP_ASID	_IOW(VHOST_VIRTIO, 0x7C, \
>  					     struct vhost_vring_state)
>  
> +/* Suspend a device so it does not process virtqueue requests anymore
> + *
> + * After the return of ioctl the device must preserve all the necessary state
> + * (the virtqueue vring base plus the possible device specific states) that is
> + * required for restoring in the future. The device must not change its
> + * configuration after that point.
> + */
> +#define VHOST_VDPA_SUSPEND		_IO(VHOST_VIRTIO, 0x7D)
> +
>  #endif
> -- 
> 2.31.1

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