Messages in this thread | | | Subject | Re: [PATCH] KVM: s390: Enable specification exception interpretation | From | Christian Borntraeger <> | Date | Tue, 6 Jul 2021 13:56:27 +0200 |
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On 06.07.21 13:52, Cornelia Huck wrote: > On Tue, Jul 06 2021, Janis Schoetterl-Glausch <scgl@linux.ibm.com> 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. >> >> Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com> >> --- >> 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; >> + if (!kvm_is_ucontrol(vcpu->kvm)) >> + vcpu->arch.sie_block->ecb |= ECB_SPECI; > > Does this exist for any hardware version (i.e. not guarded by a cpu > feature?)
Not for all hardware versions, but also no indication. The architecture says that the HW is free to do this or not. (which makes the vsie code simpler). > >> >> if (test_kvm_facility(vcpu->kvm, 8) && vcpu->kvm->arch.use_pfmfi) >> vcpu->arch.sie_block->ecb2 |= ECB2_PFMFI; >
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