This is a note to let you know that I've just added the patch titled
KVM: s390: vsie: Fix the initialization of the epoch extension (epdx) field
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-s390-vsie-fix-the-initialization-of-the-epoch-extension-epdx-field.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 0dd4cdccdab3d74bd86b868768a7dca216bcce7e Mon Sep 17 00:00:00 2001
From: Thomas Huth <thuth@xxxxxxxxxx>
Date: Wed, 23 Nov 2022 10:08:33 +0100
Subject: KVM: s390: vsie: Fix the initialization of the epoch extension (epdx) field
From: Thomas Huth <thuth@xxxxxxxxxx>
commit 0dd4cdccdab3d74bd86b868768a7dca216bcce7e upstream.
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")
Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx>
Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Reviewed-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # 4.19+
Link: https://lore.kernel.org/r/20221123090833.292938-1-thuth@xxxxxxxxxx
Message-Id: <20221123090833.292938-1-thuth@xxxxxxxxxx>
Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/s390/kvm/vsie.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/arch/s390/kvm/vsie.c
+++ b/arch/s390/kvm/vsie.c
@@ -376,8 +376,10 @@ static int shadow_scb(struct kvm_vcpu *v
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))
Patches currently in stable-queue which might be from thuth@xxxxxxxxxx are
queue-4.19/kvm-s390-vsie-fix-the-initialization-of-the-epoch-extension-epdx-field.patch
