KVM: s390: Introducing kvm_arch_set_irq_inatomic fast inject

s390 needs a fast path for irq injection, and along those lines we
introduce kvm_arch_set_irq_inatomic. Instead of placing all interrupts on
the global work queue as it does today, this patch provides a fast path for
irq injection.

The inatomic fast path cannot lose control since it is running with
interrupts disabled. This meant making the following changes that exist on
the slow path today. First, the adapter_indicators page needs to be mapped
since it is accessed with interrupts disabled, so we added map/unmap
functions. Second, access to shared resources between the fast and slow
paths needed to be changed from mutex and semaphores to spin_lock's.
Finally, the memory allocation on the slow path utilizes GFP_KERNEL_ACCOUNT
but we had to implement the fast path with GFP_ATOMIC allocation. Each of
these enhancements were required to prevent blocking on the fast inject
path.

Fencing of Fast Inject in Secure Execution environments is enabled in the
patch series by not mapping adapter indicator pages. In Secure Execution
environments the path of execution available before this patch is followed.

Statistical counters have been added to enable analysis of irq injection on
the fast path and slow path including io_390_inatomic, io_flic_inject_airq,
io_set_adapter_int and io_390_inatomic_no_inject. The no inject counter
captures adapter masked, coalesced and suppressed interrupts.

Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: Douglas Freimuth <freimuth@linux.ibm.com>
Acked-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20260604192755.203143-4-freimuth@linux.ibm.com>

0 files changed, 0 insertions, 0 deletions