Tyrel Datwyler <tyr...@linux.ibm.com> writes: > On 4/17/21 5:30 AM, Michael Ellerman wrote: >> Tyrel Datwyler <tyr...@linux.ibm.com> writes: >>> On 4/1/21 5:13 PM, Tyrel Datwyler wrote: >>>> Currently, neither the vio_bus or vio_driver structures provide support >>>> for a shutdown() routine. >>>> >>>> Add support for shutdown() by allowing drivers to provide a >>>> implementation via function pointer in their vio_driver struct and >>>> provide a proper implementation in the driver template for the vio_bus >>>> that calls a vio drivers shutdown() if defined. >>>> >>>> In the case that no shutdown() is defined by a vio driver and a kexec is >>>> in progress we implement a big hammer that calls remove() to ensure no >>>> further DMA for the devices is possible. >>>> >>>> Signed-off-by: Tyrel Datwyler <tyr...@linux.ibm.com> >>>> --- >>> >>> Ping... any comments, problems with this approach? >> >> The kexec part seems like a bit of a hack. >> >> It also doesn't help for kdump, when none of the shutdown code is run. > > If I understand correctly for kdump we have a reserved memory space where the > kdump kernel is loaded, but for kexec the memory region isn't reserved ahead > of > time meaning we can try and load the kernel over potential memory used for DMA > by the current kernel.
That's correct. >> How many drivers do we have? Can we just implement a proper shutdown for >> them? > > Well that is the end goal. I just don't currently have the bandwidth to do > each > driver myself with a proper shutdown sequence, and thought this was a > launching > off point to at least introduce the shutdown callback to the VIO bus. Fair enough. > Off the top of my head we have 3 storage drivers, 2 network drivers, vtpm, > vmc, > pseries_rng, nx, nx842, hvcs, hvc_vio. > > I can drop the kexec_in_progress hammer and just have each driver call > remove() > themselves in their shutdown function. Leave it to each maintainer to decide > if > remove() is enough or if there is a more lightweight quiesce sequence they > choose to implement. That's OK, you've convinced me. I'll take it as-is. Eventually it would be good for drivers to implement shutdown in the optimal way for their device, but that can be done incrementally. cheers
