[libvirt PATCH 6/7] nodedev: Implement virNodeDeviceIsPersistent()/IsActive()

[Jonathon Jongsma]

On Mon, Jun 14, 2021 at 12:27 PM Boris Fiuczynski <fiuczy at linux.ibm.com> wrote:
>
> On 6/3/21 10:11 PM, Jonathon Jongsma wrote:
> > Implement these new API functions in the nodedev driver.
> >
> > Signed-off-by: Jonathon Jongsma <jjongsma at redhat.com>
> > ---
> >   src/node_device/node_device_driver.c | 50 ++++++++++++++++++++++++++++
> >   src/node_device/node_device_driver.h |  6 ++++
> >   src/node_device/node_device_udev.c   | 21 +++++++-----
> >   3 files changed, 69 insertions(+), 8 deletions(-)
> >
> > diff --git a/src/node_device/node_device_driver.c b/src/node_device/node_device_driver.c
> > index 9ebe609aa4..75391f18b8 100644
> > --- a/src/node_device/node_device_driver.c
> > +++ b/src/node_device/node_device_driver.c
> > @@ -1804,3 +1804,53 @@ nodeDeviceGetAutostart(virNodeDevice *device,
> >       virNodeDeviceObjEndAPI(&obj);
> >       return ret;
> >   }
> > +
> > +
> > +int
> > +nodeDeviceIsPersistent(virNodeDevice *device)
> > +{
> > +    virNodeDeviceObj *obj = NULL;
> > +    virNodeDeviceDef *def = NULL;
> > +    int ret = -1;
> > +
> > +    if (nodeDeviceInitWait() < 0)
> > +        return -1;
> > +
> > +    if (!(obj = nodeDeviceObjFindByName(device->name)))
> > +        return -1;
> > +    def = virNodeDeviceObjGetDef(obj);
> > +
> > +    if (virNodeDeviceIsPersistentEnsureACL(device->conn, def) < 0)
> > +        goto cleanup;
> > +
> > +    ret = virNodeDeviceObjIsPersistent(obj);
> > +
> > + cleanup:
> > +    virNodeDeviceObjEndAPI(&obj);
> > +    return ret;
> > +}
> > +
> > +
> > +int
> > +nodeDeviceIsActive(virNodeDevice *device)
> > +{
> > +    virNodeDeviceObj *obj = NULL;
> > +    virNodeDeviceDef *def = NULL;
> > +    int ret = -1;
> > +
> > +    if (nodeDeviceInitWait() < 0)
> > +        return -1;
> > +
> > +    if (!(obj = nodeDeviceObjFindByName(device->name)))
> > +        return -1;
> > +    def = virNodeDeviceObjGetDef(obj);
> > +
> > +    if (virNodeDeviceIsActiveEnsureACL(device->conn, def) < 0)
> > +        goto cleanup;
> > +
> > +    ret = virNodeDeviceObjIsActive(obj);
> > +
> > + cleanup:
> > +    virNodeDeviceObjEndAPI(&obj);
> > +    return ret;
> > +}
> > diff --git a/src/node_device/node_device_driver.h b/src/node_device/node_device_driver.h
> > index d178a18180..744dd42632 100644
> > --- a/src/node_device/node_device_driver.h
> > +++ b/src/node_device/node_device_driver.h
> > @@ -180,6 +180,12 @@ int
> >   nodeDeviceGetAutostart(virNodeDevice *dev,
> >                          int *autostart);
> >
> > +int
> > +nodeDeviceIsPersistent(virNodeDevice *dev);
> > +
> > +int
> > +nodeDeviceIsActive(virNodeDevice *dev);
> > +
> >   virCommand*
> >   nodeDeviceGetMdevctlSetAutostartCommand(virNodeDeviceDef *def,
> >                                           bool autostart,
> > diff --git a/src/node_device/node_device_udev.c b/src/node_device/node_device_udev.c
> > index 21273083a6..eb15ccce7f 100644
> > --- a/src/node_device/node_device_udev.c
> > +++ b/src/node_device/node_device_udev.c
> > @@ -1487,7 +1487,7 @@ udevAddOneDevice(struct udev_device *device)
> >       virObjectEvent *event = NULL;
> >       bool new_device = true;
> >       int ret = -1;
> > -    bool was_persistent = false;
> > +    bool persistent = true;
> >       bool autostart = true;
> >       bool is_mdev;
> >
> > @@ -1518,7 +1518,8 @@ udevAddOneDevice(struct udev_device *device)
> >
> >           if (is_mdev)
> >               nodeDeviceDefCopyFromMdevctl(def, objdef);
> > -        was_persistent = virNodeDeviceObjIsPersistent(obj);
> > +
> > +        persistent = virNodeDeviceObjIsPersistent(obj);
> >           autostart = virNodeDeviceObjIsAutostart(obj);
> >
> >           /* If the device was defined by mdevctl and was never instantiated, it
> > @@ -1527,11 +1528,12 @@ udevAddOneDevice(struct udev_device *device)
> >
> >           virNodeDeviceObjEndAPI(&obj);
> >       } else {
> > -        /* All non-mdev devices report themselves as autostart since they
> > -         * should still be present and active after a reboot unless the device
> > -         * is removed from the host. Mediated devices can only be persistent if
> > -         * they are in already in the device list from parsing the mdevctl
> > -         * output. */
> > +        /* All non-mdev devices report themselves as persistent and autostart
> > +         * since they should still be present and active after a reboot unless
> > +         * the device is removed from the host. Mediated devices can only be
> > +         * persistent if they are in already in the device list from parsing
> > +         * the mdevctl output. */
>
> The assumption for all non-mdev devices ends up very misleading.
> For example: The parent device of an mdev needs to be bound to a vfio
> device driver. Without it the device ends up without the capability to
> create mdevs.
> If this driver binding is not persisted (e.g. with setting up driverctl)
> but instead the device is just manually being rebound to a vfio device
> driver than after reboot neither the mdev capability on the parent
> device nor the mdev device as a child device will be existing.
> A user calling nodedev-info before the reboot gets
> on the parent device
>         Persistent:     yes
>         Autostart:      yes
> and on the mdev device
>         Persistent:     yes
>         Autostart:      yes
> After a reboot he ends up with with nodedev-info
> on the parent device
>         Persistent:     yes
>         Autostart:      yes
> and the mdev device does not exist.

Before I get to the rest of your suggestion, I'd like to know more
about this. If the mdev device is persistent (i.e. "defined" in
mdevctl terminology), then it should still exist after a reboot, even
if it's not started. If it doesn't, then it's a bug. An mdev can be
defined even if its parent device is not present.

Does this device show up if you run 'mdevctl list --defined'?
Does it show up if you run `virsh nodedev-list --cap mdev --all`?

> I suggest to use three states like yes, no, unknown
> or not showing Persistent and Autostart on devices that libvirt does not
> manage/know about their persistence and autostart configuration.

Well, I suppose that we have the error value (-1) that could be used
for this case, but it doesn't exactly seem like an error. Adding a
separate tri-state return value would make this API inconsistent with
all of the other IsActive()/IsPersistent() APIs in libvirt, so I don't
think that's a very good idea.

Jonathon