The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 55680890ea78be0df5e1384989f1be835043c084 Mon Sep 17 00:00:00 2001
From: Christian Borntraeger borntraeger@de.ibm.com Date: Fri, 31 Jan 2020 05:02:00 -0500 Subject: [PATCH] KVM: s390: do not clobber registers during guest reset/store status
The initial CPU reset clobbers the userspace fpc and the store status ioctl clobbers the guest acrs + fpr. As these calls are only done via ioctl (and not via vcpu_run), no CPU context is loaded, so we can (and must) act directly on the sync regs, not on the thread context.
Cc: stable@kernel.org Fixes: e1788bb995be ("KVM: s390: handle floating point registers in the run ioctl not in vcpu_put/load") Fixes: 31d8b8d41a7e ("KVM: s390: handle access registers in the run ioctl not in vcpu_put/load") Signed-off-by: Christian Borntraeger borntraeger@de.ibm.com Reviewed-by: David Hildenbrand david@redhat.com Reviewed-by: Cornelia Huck cohuck@redhat.com Signed-off-by: Janosch Frank frankja@linux.ibm.com Link: https://lore.kernel.org/r/20200131100205.74720-2-frankja@linux.ibm.com Signed-off-by: Christian Borntraeger borntraeger@de.ibm.com
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index d9e6bf3d54f0..876802894b35 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -2860,9 +2860,7 @@ static void kvm_s390_vcpu_initial_reset(struct kvm_vcpu *vcpu) vcpu->arch.sie_block->gcr[14] = CR14_UNUSED_32 | CR14_UNUSED_33 | CR14_EXTERNAL_DAMAGE_SUBMASK; - /* make sure the new fpc will be lazily loaded */ - save_fpu_regs(); - current->thread.fpu.fpc = 0; + vcpu->run->s.regs.fpc = 0; vcpu->arch.sie_block->gbea = 1; vcpu->arch.sie_block->pp = 0; vcpu->arch.sie_block->fpf &= ~FPF_BPBC; @@ -4351,7 +4349,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp, switch (ioctl) { case KVM_S390_STORE_STATUS: idx = srcu_read_lock(&vcpu->kvm->srcu); - r = kvm_s390_vcpu_store_status(vcpu, arg); + r = kvm_s390_store_status_unloaded(vcpu, arg); srcu_read_unlock(&vcpu->kvm->srcu, idx); break; case KVM_S390_SET_INITIAL_PSW: {