On Wed, Jul 07 2021, Christian Borntraeger <borntraeger@xxxxxxxxxx> wrote: > On 06.07.21 13:47, Janis Schoetterl-Glausch wrote: >> When this feature is enabled the hardware is free to interpret >> specification exceptions generated by the guest, instead of causing >> program interruption interceptions. >> >> This benefits (test) programs that generate a lot of specification >> exceptions (roughly 4x increase in exceptions/sec). >> >> Interceptions will occur as before if ICTL_PINT is set, >> i.e. if guest debug is enabled. > > I think I will add > > There is no indication if this feature is available or not and the hardware > is free to interpret or not. So we can simply set this bit and if the > hardware ignores it we fall back to intercept 8 handling. Sounds good. > > > With that > > Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxx> >> >> Signed-off-by: Janis Schoetterl-Glausch <scgl@xxxxxxxxxxxxx> >> --- >> I'll additionally send kvm-unit-tests for testing this feature. >> >> arch/s390/include/asm/kvm_host.h | 1 + >> arch/s390/kvm/kvm-s390.c | 2 ++ >> arch/s390/kvm/vsie.c | 2 ++ >> 3 files changed, 5 insertions(+) (...) >> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c >> index b655a7d82bf0..aadd589a3755 100644 >> --- a/arch/s390/kvm/kvm-s390.c >> +++ b/arch/s390/kvm/kvm-s390.c >> @@ -3200,6 +3200,8 @@ static int kvm_s390_vcpu_setup(struct kvm_vcpu *vcpu) >> vcpu->arch.sie_block->ecb |= ECB_SRSI; >> if (test_kvm_facility(vcpu->kvm, 73)) >> vcpu->arch.sie_block->ecb |= ECB_TE; Maybe add /* no facility bit, but safe as the hardware may ignore it */ or something like that, so that we don't stumble over that in the future? >> + if (!kvm_is_ucontrol(vcpu->kvm)) >> + vcpu->arch.sie_block->ecb |= ECB_SPECI; >> >> if (test_kvm_facility(vcpu->kvm, 8) && vcpu->kvm->arch.use_pfmfi) >> vcpu->arch.sie_block->ecb2 |= ECB2_PFMFI; Reviewed-by: Cornelia Huck <cohuck@xxxxxxxxxx>
