kernel/git/stable/linux.git/drivers/s390/cio, branch linux-7.2.y

s390/vfio_ccw: Implement a crw lock

2026-07-30T17:50:48+00:00

Unlike the channel_program struct, which covers synchronous I/O submissions and asynchronous interrupts, the CRW region relies exclusively on asynchronous events coming from hardware. Implement a lock to manage the list of those payloads, to ensure they are read cohesively. Fixes: 3f02cb2fd9d2 ("vfio-ccw: Wire up the CRW irq and CRW region") Cc: stable@vger.kernel.org Reviewed-by: Matthew Rosato Reviewed-by: Farhan Ali Signed-off-by: Eric Farman Signed-off-by: Christian Borntraeger

s390/vfio_ccw: Selectively expand io_mutex

2026-07-30T17:50:43+00:00

The io_mutex was defined to serialize the io_regions, but then has also sort of been associated with the I/O themselves because of the close relationship they share. With the handful of races that are possible, the choices are either to: A) expand the scope of io_mutex to close these remaining windows, or B) reduce the scope of io_mutex to just io_region, and introduce a new lock mechanism for the remaining I/O resources This patch implements A, since B brings with it a lot more interactions that would need to be tracked and kept in a correct hierarchy. It also takes advantage of the workqueue element for cp_free() that now gets called out of fsm_notoper(), which could be invoked out of an interrupt context and thus cannot acquire a mutex itself. Fixes: 4f76617378ee ("vfio-ccw: protect the I/O region") Cc: stable@vger.kernel.org Signed-off-by: Eric Farman Reviewed-by: Matthew Rosato Signed-off-by: Christian Borntraeger

s390/vfio_ccw: Move cp cleanup out of not operational

2026-07-30T17:50:39+00:00

The fsm_notoper() routine is called when the device has been lost, and is (by definition) no longer operational. Since this can happen asynchronously from the normal behavior of the driver, the cleanup may happen when holding other locks in the calling sequence (notably, the cio subchannel lock). Push the cleanup of the private->cp resources to a workqueue, where it can be done out from under that lock sequence and a future patch can safely manage the locking requirements. Fixes: 204b394a23ad ("vfio/ccw: Move FSM open/close to MDEV open/close") Cc: stable@vger.kernel.org Signed-off-by: Eric Farman Reviewed-by: Matthew Rosato Signed-off-by: Christian Borntraeger

s390/vfio_ccw: Cancel existing workqueues

2026-07-30T17:50:31+00:00

The initialization of the io_work and crw_work workqueues begs the question of whether they should be un-initialized. Add the corresponding cleanup tags in _release_dev to ensure work isn't dispatched after the private struct is free'd. Suggested-by: Matthew Rosato Fixes: e5f84dbaea59 ("vfio: ccw: return I/O results asynchronously") Fixes: 3f02cb2fd9d2 ("vfio-ccw: Wire up the CRW irq and CRW region") Cc: stable@vger.kernel.org Reviewed-by: Matthew Rosato Signed-off-by: Eric Farman Signed-off-by: Christian Borntraeger

s390/vfio_ccw: Ensure index for read/write regions are within range

2026-07-30T17:50:24+00:00

The introduction of the capability chain rightly clamped the region indexes to the range of the capabilities itself, but neglected to do so for the existing read/write regions which should also be enforced. Fixes: db8e5d17ac03 ("vfio-ccw: add capabilities chain") Cc: stable@vger.kernel.org Cc: Cornelia Huck Reviewed-by: Matthew Rosato Signed-off-by: Eric Farman Signed-off-by: Christian Borntraeger

s390/vfio_ccw: Calculate idal length based on idaw type

2026-07-30T17:50:19+00:00

Sashiko pointed out that get_guest_idal() unconditionally calculates the length of the IDAL presuming everything is a Format-2 IDAW. The output of vfio-ccw is always Format-2, but the input can be either Format-1 (31-bit addresses) or Format-2 (64-bit addresses). As a result, the size of the guest IDAL may be incorrect and should be trimmed down. Reported-by: sashiko-bot Link: https://lore.kernel.org/r/20260720203400.7328E1F000E9@smtp.kernel.org/ Fixes: 1b676fe3d9d3 ("vfio/ccw: handle a guest Format-1 IDAL") Cc: stable@vger.kernel.org Reviewed-by: Matthew Rosato Signed-off-by: Eric Farman Signed-off-by: Christian Borntraeger

s390/vfio_ccw: Ensure first IDAW remains constant

2026-07-30T17:50:15+00:00

The first IDAW in a list does not need to be on a 2K/4K boundary like all others, and so is read separately to accurately calculate the size of the buffer needed to read the full IDAL. Verify that the address found in the first IDAW is unchanged between reads, to ensure a consistent set of IDAWs being worked with. Fixes: 01aa26c672c0 ("s390/cio: Combine direct and indirect CCW paths") Cc: stable@vger.kernel.org Reviewed-by: Matthew Rosato Signed-off-by: Eric Farman Signed-off-by: Christian Borntraeger

s390/vfio_ccw: Fix out of bounds check on CCW array

2026-07-30T17:50:11+00:00

The routine ccwchain_calc_length() counts the number of channel command words (CCWs) that are chained together in a single channel program, and rejects anything larger than CCWCHAIN_LEN_MAX (256) CCWs. The loop itself is "do..while (count < 257)", and while the logic in is_cpa_within_range() correctly adjusts between the 0-index array of CCWs and the count of CCWs starting at 1, this means it would look at a possible 257th CCW before ending the loop and (correctly) returning an error. Fix this by restructuring the loop to break as soon as 256 CCWs (thus indexes 0-255) are examined, without looking at memory outside the range. Fixes: 0a19e61e6d4c ("vfio: ccw: introduce channel program interfaces") Cc: stable@vger.kernel.org Reviewed-by: Matthew Rosato Signed-off-by: Eric Farman Signed-off-by: Christian Borntraeger

s390/vfio_ccw: Limit the number of channel program segments

2026-07-30T17:50:07+00:00

The processing of channel programs, and the CCWs within them, is done recursively. As such, there is an arbitrary (but not architectural) limit to the number of CCWs that can exist in a single channel program. The vfio-ccw logic breaks these channel programs into segments whenever it encounters a Transfer-In-Channel (TIC) CCW, and the combined number of segments count towards the global limit. Impose an equivalent limit to the number of segments until such logic can be made non-recursive. Fixes: 0a19e61e6d4c ("vfio: ccw: introduce channel program interfaces") Cc: stable@vger.kernel.org Reviewed-by: Matthew Rosato Signed-off-by: Eric Farman Signed-off-by: Christian Borntraeger

s390/vfio_ccw: Free all memory if cp_init() fails

2026-07-30T17:49:49+00:00

The routine cp_free() is called to unpin/free any memory once an I/O is completed successfully, or if cp_prefetch() fails. But if cp_init() fails, and cp->initialized is not enabled, the same routine cannot be used to free all the memory. An attempt to address this exists in ccwchain_handle_ccw(), where a single call to ccwchain_free() is made for the currently-processed CCW segment. But this will leak other segments (created as a result of a Transfer in Channel) that had been allocated as part of the same channel program. Address this by performing the cleanup outside of the recursive ccwchain_handle_ccw()/ccwchain_loop_tic() logic. Fixes: 8b515be512a2 ("vfio-ccw: Fix memory leak and don't call cp_free in cp_init") Cc: stable@vger.kernel.org Reviewed-by: Farhan Ali Reviewed-by: Matthew Rosato Signed-off-by: Eric Farman Signed-off-by: Christian Borntraeger