On Tue, Sep 08, 2026 at 07:38:11AM +0200, Karl Mehltretter wrote:
> This is v3 of the callback synchronization series. It is based on
> Michael S. Tsirkin's linux-next branch at f49e6cf91942 ("virtio:
> synchronize callbacks after device reset"), which already contains the
> core change and the virtio_input teardown reorder from v2.Thanks I applied since this looks like a net improvement. Pls keep iterating on the core change. If you want to take a stab at some of the pre-existing issues - will be welcome. Pls do note which patches were tested and which were not. > Patches 1 and 2 fix two bugs in virtio-ccw's existing > synchronize_cbs() hook. After a fallback from adapter to classic > interrupts it selects the wrong lock, and the classic interrupt handler > only takes the matching lock when notification hardening is enabled. > Patch 3 adds SRCU tracking for remoteproc callbacks, which can sleep. > Patches 4 and 5 replace the RCU fallback with synchronization against > the UML IRQ and the TmFIFO callback locks. The fallback already covers > these IRQ handlers and spinlock sections. Patch 6 adds SRCU tracking > in virtio_vdpa so callback synchronization does not depend on the > context in which the vDPA driver invokes the callback. > > The UML, TmFIFO and remoteproc reset paths do not themselves prevent > new virtqueue callbacks. UML and TmFIFO only clear a status field, and > remoteproc does not wait for the remote side to acknowledge the reset. > Without notification hardening or driver-specific teardown protection, > callbacks can still start after reset. The new synchronization hooks > do not fix that. The TmFIFO hook also does not synchronize with the > rest of the FIFO work item outside the callback locks. > > The virtio_input loop change from v2 (continue instead of break, so > events the device already completed are still delivered) and the > event buffer leak are sent separately. > > Changes in v3: > - Rebased on Michael's linux-next branch. Dropped the core change and > the virtio_input patch, which are there already. > - Split the virtio-ccw fixes out of the core patch, one per bug, and > the transport patch into one patch per transport. The CCW and TmFIFO > changes are functionally unchanged from v2. > - Patch 2: added a Fixes tag and described the existing shutdown > case. Removed the dependency note on the core reset change. > - remoteproc: read the queue pointer once in rproc_vq_interrupt(), and > synchronize with callbacks in __rproc_virtio_del_vqs() before > freeing the queues (Sashiko). Place vq_srcu next to rvdevs so the > hunk also applies to mainline, which added attach_work after index. > - virtio_uml: compare against UM_IRQ_ALLOC instead of a bare negative > check. > - virtio_vdpa: use SRCU instead of a per-device rwlock, so the > callback tracking uses per-CPU counters, and cover the config > callback (Sashiko). > - Rewrote the commit messages. Corrected the RCU fallback description > for UML, TmFIFO and the vDPA simulators. Dropped the claimed simulator > reset race: the simulators disable bottom halves around virtqueue > callbacks and serialize reset with the worker's mutex. > > Changes in v2: > - Moved callback synchronization from virtio-pci into the core, as > Michael suggested, and added the missing synchronize_cbs() hooks. > > Testing: the changed objects build with W=1 without warnings, with > clang on arm64, x86-64 and s390 and with gcc on SMP UML, and the > patches also apply to current mainline and linux-next. The runtime > tests from v2 were not repeated on this version: the input, rebind and > shutdown checks on arm64 MMIO and x86 PCI covered code that is > unchanged here, and the remoteproc and virtio_vdpa hooks have only > been build-tested. No remoteproc, TmFIFO or s390 hardware was > available. > > v2: https://lore.kernel.org/r/[email protected] > v1: https://lore.kernel.org/r/[email protected] > > Karl Mehltretter (6): > virtio_ccw: fix synchronize_cbs() after interrupt fallback > virtio_ccw: always take irq_lock in the classic interrupt handler > remoteproc: implement synchronize_cbs() for virtio devices > um: virtio_uml: implement synchronize_cbs() > platform/mellanox: mlxbf-tmfifo: implement synchronize_cbs() > virtio_vdpa: implement synchronize_cbs() > > arch/um/drivers/virtio_uml.c | 10 +++++++ > drivers/platform/mellanox/mlxbf-tmfifo.c | 15 ++++++++++ > drivers/remoteproc/remoteproc_core.c | 12 ++++++++ > drivers/remoteproc/remoteproc_virtio.c | 37 +++++++++++++++++++----- > drivers/s390/virtio/virtio_ccw.c | 6 +--- > drivers/virtio/virtio_vdpa.c | 34 ++++++++++++++++++++-- > include/linux/remoteproc.h | 3 ++ > 7 files changed, 102 insertions(+), 15 deletions(-) > > > base-commit: f49e6cf919425cc55f10fd7cda7e0fc895df4cc0 > -- > 2.39.5 (Apple Git-154)
