Re: [PATCH v5 2/4] s390/pci: Preserve FMB state in device re-enablement

[Niklas Schnelle <schnelle@linux.ibm.com>]

On Fri, 2026-06-26 at 13:55 -0400, Omar Elghoul wrote:
> Introduce a function zpci_fmb_reenable_device() that checks the state of
> the FMB and ensures it is enabled. Reset the counters to zero, disable, and
> re-enable the FMB if it was already enabled. Call this function during a
> zPCI device re-enablement, which in turn implicitly ensures that the FMB is
> enabled for host devices during their KVM registration.
> 
> Signed-off-by: Omar Elghoul <oelghoul@linux.ibm.com>
> ---

Just to keep the list up to date. We're still discussing some details
about this internally. Mostly about how this may interact with platform
behavior in some edge cases that are likely not possible with current
implementations but would be covered by the architecture. 

Personally, I actually liked the re-using of the buffer in v4 better
and I think depending on implementations of the kmem_cache,
specifically if it may give us back the same buffer that we just freed
in the immediately following allocation, this could also end up re-
using the same buffer anyway. Hope to get the details sorted soon.

Thanks,
Niklas