eventfd: simplify eventfd_signal()

Ever since the eventfd type was introduced back in 2007 in commit
e1ad7468c77d ("signal/timer/event: eventfd core") the eventfd_signal()
function only ever passed 1 as a value for @n. There's no point in
keeping that additional argument.

Link: https://lore.kernel.org/r/20231122-vfs-eventfd-signal-v2-2-bd549b14ce0c@kernel.org
Acked-by: Xu Yilun <yilun.xu@intel.com>
Acked-by: Andrew Donnellan <ajd@linux.ibm.com> # ocxl
Acked-by: Eric Farman <farman@linux.ibm.com> # s390
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Christian Brauner <brauner@kernel.org>

vfio/ccw: remove private->sch

These places all rely on the ability to jump from a private
struct back to the subchannel struct. Rather than keeping a
copy in our back pocket, let's use the relationship provided
by the vfio_device embedded within the private.

Signed-off-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Link: https://lore.kernel.org/r/20221104142007.1314999-3-farman@linux.ibm.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

vfio-ccw: Fix a build error due to missing include of linux/slab.h

Include linux/slab.h to fix a build error due to kfree() being undefined.

Fixes: 3f02cb2fd9d2 ("vfio-ccw: Wire up the CRW irq and CRW region")
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200703022628.6036-1-sean.j.christopherson@intel.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

vfio-ccw: make vfio_ccw_regops variables declarations static

Fixes the following sparse warnings:
drivers/s390/cio/vfio_ccw_chp.c:62:30: warning: symbol 'vfio_ccw_schib_region_ops' was not declared. Should it be static?
drivers/s390/cio/vfio_ccw_chp.c:117:30: warning: symbol 'vfio_ccw_crw_region_ops' was not declared. Should it be static?

Link: https://lkml.kernel.org/r/patch.git-a34be7aede18.your-ad-here.call-01591269421-ext-5655@work.hours
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

vfio-ccw: Wire up the CRW irq and CRW region

Use the IRQ to notify userspace that there is a CRW
pending in the region, related to path-availability
changes on the passthrough subchannel.

Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
Signed-off-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20200505122745.53208-8-farman@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

vfio-ccw: Introduce a new CRW region

This region provides a mechanism to pass a Channel Report Word
that affect vfio-ccw devices, and needs to be passed to the guest
for its awareness and/or processing.

The base driver (see crw_collect_info()) provides space for two
CRWs, as a subchannel event may have two CRWs chained together
(one for the ssid, one for the subchannel). As vfio-ccw will
deal with everything at the subchannel level, provide space
for a single CRW to be transferred in one shot.

Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
Signed-off-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20200505122745.53208-7-farman@linux.ibm.com>
[CH: added padding to ccw_crw_region]
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

vfio-ccw: Introduce a new schib region

The schib region can be used by userspace to get the subchannel-
information block (SCHIB) for the passthrough subchannel.
This can be useful to get information such as channel path
information via the SCHIB.PMCW fields.

Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
Signed-off-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20200505122745.53208-5-farman@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>