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

Nico Boehr
2023-10-09T09:33:14Z

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(-)

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2.41.0