KVM: s390: pci: Fix GISC refcount leak on AIF enable failure

KVM: s390: pci: Fix GISC refcount leak on AIF enable failure

kvm_s390_gisc_register() registers the guest ISC before pinning
the guest interrupt forwarding pages and allocating the AISB bit.
If any of the later setup steps fails, the function unwinds the
pinned pages and other local state, but does not unregister the
GISC reference. Add the missing kvm_s390_gisc_unregister() to the
error unwind path.

Fixes: 3c5a1b6f0a18 ("KVM: s390: pci: provide routines for enabling/disabling interrupt forwarding")
Cc: stable@vger.kernel.org
Signed-off-by: Haoxiang Li <haoxiang_li2024@163.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Tested-by: Matthew Rosato <mjrosato@linux.ibm.com>
Acked-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20260624061910.2794734-1-haoxiang_li2024@163.com>
Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>