On 7/6/21 5:16 PM, David Hildenbrand wrote: > On 06.07.21 14:02, Christian Borntraeger wrote: >> >> >> On 06.07.21 13:59, David Hildenbrand wrote: >>> On 06.07.21 13:56, Christian Borntraeger wrote: >>>> >>>> >>>> On 06.07.21 13:52, Cornelia Huck wrote: >>>>> On Tue, Jul 06 2021, Janis Schoetterl-Glausch <scgl@xxxxxxxxxxxxx> 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@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; >>>>>> + 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). >>> >>> I remember the architecture said at some point to never set undefined bits - and this bit is undefined on older HW generations. I might be wrong, though. >> >> I can confirm that this bit will be ignored on older machines. The notion of >> never setting undefined bits comes from "you never know what this bit will >> change in future machines". Now we know :-) > > Well, okay then :) > > So the plan for vSIE is to always keep it disabled? IIUC, one could similarly always forward the bit of set. The bit does get copied for vSIE.
