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 though HW learned the lesson to always use proper feature indications
along with new features)
--
Thanks,
David / dhildenb
