Messages in this thread | | | Date | Thu, 24 Nov 2022 11:24:33 +0100 | Subject | Re: [PATCH] KVM: s390: vsie: Fix the initialization of the epoch extension (epdx) field | From | Janosch Frank <> |
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On 11/23/22 10:41, Christian Borntraeger wrote: > > > Am 23.11.22 um 10:08 schrieb Thomas Huth: >> We recently experienced some weird huge time jumps in nested guests when >> rebooting them in certain cases. After adding some debug code to the epoch >> handling in vsie.c (thanks to David Hildenbrand for the idea!), it was >> obvious that the "epdx" field (the multi-epoch extension) did not get set >> to 0xff in case the "epoch" field was negative. >> Seems like the code misses to copy the value from the epdx field from >> the guest to the shadow control block. By doing so, the weird time >> jumps are gone in our scenarios. >> >> Link: https://bugzilla.redhat.com/show_bug.cgi?id=2140899 >> Fixes: 8fa1696ea781 ("KVM: s390: Multiple Epoch Facility support") > > We might want to add cc stable, just in case.
I'm pushing this to devel for the CI with the following additions:
Reviewed-by: Janosch Frank <frankja@linux.ibm.com> Cc: stable@vger.kernel.org # 4.19+
> > Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com> > > >> Signed-off-by: Thomas Huth <thuth@redhat.com> >> --- >> arch/s390/kvm/vsie.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c >> index 94138f8f0c1c..ace2541ababd 100644 >> --- a/arch/s390/kvm/vsie.c >> +++ b/arch/s390/kvm/vsie.c >> @@ -546,8 +546,10 @@ static int shadow_scb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page) >> if (test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_CEI)) >> scb_s->eca |= scb_o->eca & ECA_CEI; >> /* Epoch Extension */ >> - if (test_kvm_facility(vcpu->kvm, 139)) >> + if (test_kvm_facility(vcpu->kvm, 139)) { >> scb_s->ecd |= scb_o->ecd & ECD_MEF; >> + scb_s->epdx = scb_o->epdx; >> + } >> >> /* etoken */ >> if (test_kvm_facility(vcpu->kvm, 156))
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