On Mon, 15 Jun 2026 16:01:55 -0400 William Bezenah <[email protected]> wrote:
> On 6/15/2026 10:58 AM, Cornelia Huck wrote: > > On Mon, Jun 15 2026, Halil Pasic <[email protected]> wrote: > > > >> On Fri, 12 Jun 2026 17:54:07 +0200 > >> William Bezenah <[email protected]> wrote: > >> > >>> Since commit 8c58a229688c ("s390/cio: Do not unregister the > >>> subchannel based on DNV"), subchannel behavior following a device > >>> detach has been updated and results in -EINVAL being propagated > >>> rather than -ENODEV, originating from ccw_device_start_timeout_key() > >>> in cio/device_ops. In the end, the virtio driver has no ability to > >>> react to the difference between device and subchannel states here, > >>> and during detach, both -ENODEV and -EINVAL indicate the device > >>> cannot be used and should not be treated as errors requiring > >>> attention. Update error handling in virtio_ccw_del_vq() and > >>> virtio_ccw_drop_indicator() to suppress -EINVAL in addition to > >>> -ENODEV. > >> Hi William! > >> > >> Are you saying that ccw_device_start() started returning -EINVAL > >> since 8c58a229688c ("s390/cio: Do not unregister the subchannel based on > >> DNV")? Or did I somehow read the paragraph wrong? > >> > >> The funcition ccw_device_start is documented to return: > >> * Returns: > >> > >> * %0, if the operation was successful; > >> > >> * -%EBUSY, if the device is busy, or status pending; > >> > >> * -%EACCES, if no path specified in @lpm is operational; > >> > >> * -%ENODEV, if the device is not operational. > >> and the commit message does not say a thing about introducing -EINVAL to > >> the mix. > > The function may return -EINVAL for non-enabled subchannels > > (i.e. pmcw.ena == 0), maybe we get an all-zeroes schib with dnv == 0? > > I'd expect it not to be enabled in that case anyway. > > Yep, that's at least how I've come to understand what changed. The > function ccw_device_start_timeout_key() has always returned -EINVAL > for non-enabled subchannels (pmcw.ena == 0), though it's not > documented in the header. Wasn't his -EINVAL actually introduced by commit: 823d494ac111 ("[S390] pm: ccw bus power management callbacks")? > > What changed with commit 8c58a229688c is that cio_update_schib() now > updates the schib even when DNV=0, rather than returning early as it > did previously. Somehow this update results in pmcw.ena == 0 in > ccw_device_start_timeout_key(). Previously, it saw pmcw.ena == 1 and > moved to the condition (cdev->private->state == DEV_STATE_NOT_OPER) > where it returned -ENODEV. Sounds fishy to me. As far as I understand the DNV takes precedence over all other pieces of PMCW. > > So the commit didn't introduce -EINVAL as a new return value, rather, > it changed the subchannel lifecycle such that existing paths now > propagate -EINVAL rather than -ENODEV during the device detach > scenario. > I'm not convinced returning -EINVAL in the given situation is the right thing to do. Peter, would you mind to chime in? Regards, Halil
