KVM: s390: do not clobber registers during guest reset/store status

BugLink: https://bugs.launchpad.net/bugs/1863588
commit 55680890ea78be0df5e1384989f1be835043c084 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index d047e846e1b9f2e6795e46564543f70c4233ca8a..756c627f7e540809192c96ef35a2d714305cabc2 100644 (file)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2863,9 +2863,7 @@ 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;
@@ -4354,7 +4352,7 @@ 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: {