Polite ping. Quoting Nico Boehr (2023-05-10 14:18:20) > 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. > > While developing this, a question regarding the stat counters came up: > there's usually no locking involved when the stat counters are incremented. > On s390, GCC accidentally seems to do the right thing(TM) most of the time > by generating a agsi instruction (which should be atomic given proper > alignment). However, it's not guaranteed, so would we rather want to go > with an atomic for the stat counters to avoid losing events? Or do we just > accept the fact that we might loose events sometimes? Is there anything > that speaks against having an atomic in kvm_stat? > > 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 | 6 ++++++ > arch/s390/kvm/gaccess.c | 7 +++++++ > arch/s390/kvm/kvm-s390.c | 10 +++++++++- > arch/s390/kvm/trace-s390.h | 23 +++++++++++++++++++++++ > arch/s390/kvm/vsie.c | 1 + > 5 files changed, 46 insertions(+), 1 deletion(-) > > -- > 2.39.1 >
