[PATCH v2 0/3] KVM: arm64: add more event counters for kvm_stat

[Yoan Picchi]

Hi all,

Considering the feedback on my first version https://lore.kernel.org/linux-arm-kernel/20210319161711.24972-1-yoan.picchi@arm.com/
I started from scratch and focussed only on stage 2 page fault.

For the context, as mentioned in the KVM forum talk from 2019 
(https://kvmforum2019.sched.com/event/Tmwf/kvmstat-and-beyond-past-present-and-future-of-performance-monitoring-christian-borntrager-ibm page 10),
there are few event counters for kvm_stat in the arm64 version of kvm when
you compare it to something like the x86 version.
Those counters are used in kvm_stat by kernel/driver developers to
have a rough idea of the impact of their patches on the general performance.

In this patchset I introduce 3 counters to use in kvm stat. They aim to help
a kernel/driver dev troubleshot performance issues by letting them know how
much exits comes from stage 2 table faults, and thus, see if their changes
added a lot. Between the existing mmio_user_exit and the added page_mapped,
the main reasons for a stage 2 page fault should be covered and thus give
some finer granularity when looking for the source of exits.


Yoan Picchi (3):
  KVM: arm64: Add a stage2 page fault counter for kvm_stat
  KVM: arm64: Add two page mapping counters for kvm_stat
  KVM: arm64: Add irq_exit counter for kvm_stat

 arch/arm64/include/asm/kvm_host.h | 4 ++++
 arch/arm64/kvm/guest.c            | 4 ++++
 arch/arm64/kvm/handle_exit.c      | 1 +
 arch/arm64/kvm/hyp/pgtable.c      | 5 +++++
 arch/arm64/kvm/mmu.c              | 2 ++
 5 files changed, 16 insertions(+)

-- 
2.17.1