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. 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. 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.
