[libvirt PATCH 6/7] nodedev: Implement virNodeDeviceIsPersistent()/IsActive()
Jonathon Jongsma
jjongsma at redhat.com
Wed Jun 23 19:12:06 UTC 2021
On Wed, Jun 16, 2021 at 8:30 AM Boris Fiuczynski <fiuczy at linux.ibm.com> wrote:
>
> On 6/14/21 10:46 PM, Jonathon Jongsma wrote:
> > 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'?
>
> Yes, the mdev definition exists.
> Here is the information before the reboot with a vfio-ccw device setup
> by manually binding it to the vfio-ccw device driver. Manually means
> that I did not use driverctl to persist the device driver binding.
>
> # virsh nodedev-info mdev_e60cef97_3f6b_485e_ac46_0520f9f66ac2
> Name: mdev_e60cef97_3f6b_485e_ac46_0520f9f66ac2
> Parent: css_0_0_0033
> Active: yes
> Persistent: yes
> Autostart: yes
>
> # mdevctl list -d
> e60cef97-3f6b-485e-ac46-0520f9f66ac2 0.0.0033 vfio_ccw-io auto (active)
>
> # virsh nodedev-dumpxml mdev_e60cef97_3f6b_485e_ac46_0520f9f66ac2
> <device>
> <name>mdev_e60cef97_3f6b_485e_ac46_0520f9f66ac2</name>
>
> <path>/sys/devices/css0/0.0.0033/e60cef97-3f6b-485e-ac46-0520f9f66ac2</path>
> <parent>css_0_0_0033</parent>
> <driver>
> <name>vfio_mdev</name>
> </driver>
> <capability type='mdev'>
> <type id='vfio_ccw-io'/>
> <uuid>e60cef97-3f6b-485e-ac46-0520f9f66ac2</uuid>
> <iommuGroup number='1'/>
> </capability>
> </device>
>
> # virsh nodedev-info css_0_0_0033
> Name: css_0_0_0033
> Parent: computer
> Active: yes
> Persistent: yes
> Autostart: yes
>
> This is the state before rebooting.
> After the reboot:
> # virsh nodedev-list --tree
> ...
> +- css_0_0_0033
> | |
> | +- ccw_0_0_c670
> | |
> | +- block_dasdb_IBM_750000000KMV11_c600_70
> |
> +- css_0_0_0034
> | |
> | +- ccw_0_0_c671
> | |
> | +- block_dasda_IBM_750000000KMV11_c600_71
> ...
>
> # virsh nodedev-info css_0_0_0033
> Name: css_0_0_0033
> Parent: computer
> Active: yes
> Persistent: yes
> Autostart: yes
>
> # virsh nodedev-info ccw_0_0_c670
> Name: ccw_0_0_c670
> Parent: css_0_0_0033
> Active: yes
> Persistent: yes
> Autostart: yes
>
> # virsh nodedev-dumpxml css_0_0_0033
> <device>
> <name>css_0_0_0033</name>
> <path>/sys/devices/css0/0.0.0033</path>
> <parent>computer</parent>
> <driver>
> <name>io_subchannel</name>
> </driver>
> <capability type='css'>
> <cssid>0x0</cssid>
> <ssid>0x0</ssid>
> <devno>0x0033</devno>
> </capability>
> </device>
>
> # virsh nodedev-list --cap mdev --all
> mdev_e60cef97_3f6b_485e_ac46_0520f9f66ac2
>
> # virsh nodedev-info mdev_e60cef97_3f6b_485e_ac46_0520f9f66ac2
> Name: mdev_e60cef97_3f6b_485e_ac46_0520f9f66ac2
> Parent: 0.0.0033
> Active: no
> Persistent: yes
> Autostart: yes
>
> As you can see the default device driver is bound to the parent device
> now and therefore the mdev does not get created although being defined
> in mdevctl.
> Also note that Persistent ond Autostart are misleading as they show on
> the mdev definition as well as the ccw device being set both "yes".
>
> On s390 there is also cio_ignore which allows devices to be ignored.
> This can also cause that devices exist before the reboot afterwards due
> to being ignored no longer exist on the system.
>
> For these reasons I think that these two new attributes show something
> that libvirt should not make assumptions on unless knowing about it.
>
This is an interesting case. The vast majority of these devices will
be "persistent" for all practical purposes, because they will still be
there on the next reboot, and they will still be using the same
drivers. On the other hand, it is true that there is no record of the
device that remains after the physical device is removed, so strictly
speaking they're not persistently defined. After reflecting, I've kind
of flip-flopped and decided that maybe the best choice would be to
mark them as non-persistent (and also non-autostart?). Would there be
any downside to such a designation? They don't exactly match the
behavior of other transient objects (domains, etc) because they
(mostly) will still be present after a reboot...I still don't really
like the idea of introducing a tristate return type. Opinions from
longtime libvirt developers particularly appreciated.
Jonathon
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