[v4,0/2] KVM: s390: add counters for vsie performance

Message

Nico Boehr Oct. 9, 2023, 9:32 a.m. UTC

v4:
---
* fix indent in tracepoint (thanks Janosch)

v3:
---
* rename te -> entry (David)
* add counters for gmap reuse and gmap create (David)

v2:
---
* also count shadowing of pages (Janosch)
* fix naming of counters (Janosch)
* mention shadowing of multiple levels is counted in each level (Claudio)
* fix inaccuate commit description regarding gmap notifier (Claudio)

When running a guest-3 via VSIE, guest-1 needs to shadow the page table
structures of guest-2.

To reflect changes of the guest-2 in the _shadowed_ page table structures,
the _shadowing_ sturctures sometimes need to be rebuilt. Since this is a
costly operation, it should be avoided whenever possible.

This series adds kvm stat counters to count the number of shadow gmaps
created and a tracepoint whenever something is unshadowed. This is a first
step to try and improve VSIE performance.

Please note that "KVM: s390: add tracepoint in gmap notifier" has some
checkpatch --strict findings. I did not fix these since the tracepoint
definition would then look completely different from all the other
tracepoints in arch/s390/kvm/trace-s390.h. If you want me to fix that,
please let me know.

Nico Boehr (2):
  KVM: s390: add stat counter for shadow gmap events
  KVM: s390: add tracepoint in gmap notifier

 arch/s390/include/asm/kvm_host.h |  7 +++++++
 arch/s390/kvm/gaccess.c          |  7 +++++++
 arch/s390/kvm/kvm-s390.c         | 11 ++++++++++-
 arch/s390/kvm/trace-s390.h       | 23 +++++++++++++++++++++++
 arch/s390/kvm/vsie.c             |  5 ++++-
 5 files changed, 51 insertions(+), 2 deletions(-)