[PATCH v3 1/5] KVM: s390: Silence potential warnings in _gmap_crstep_xchg_atomic()

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

While dat_crstep_xchg_atomic() is marked as __must_check, in this
particular case the return value should be ignored.

Silence potential compiler warnings with a pointless check, and add a
comment to explain the situation.

Fixes: d1adc098ce08 ("KVM: s390: Fix _gmap_crstep_xchg_atomic()")
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
CC: stable@vger.kernel.org # 7.1
---
 arch/s390/kvm/gmap.h | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/s390/kvm/gmap.h b/arch/s390/kvm/gmap.h
index 5374f21aaf8d..20881e3ce9d8 100644
--- a/arch/s390/kvm/gmap.h
+++ b/arch/s390/kvm/gmap.h
@@ -279,7 +279,16 @@ static inline bool __must_check _gmap_crstep_xchg_atomic(struct gmap *gmap, unio
 			gmap_handle_vsie_unshadow_event(gmap, gfn);
 		else
 			_gmap_handle_vsie_unshadow_event(gmap, gfn);
-		dat_crstep_xchg_atomic(crstep, oldcrste, newcrste, gfn, gmap->asce);
+		if (!dat_crstep_xchg_atomic(crstep, oldcrste, newcrste, gfn, gmap->asce))
+			return false;
+		/*
+		 * Return false even if the swap was successful, as it only
+		 * indicates that the best effort clearing of the vsie_notif
+		 * bit was successful. The caller will have to try again
+		 * regardless, since the desired value has not been set.
+		 * This pointless check is needed to silence a potential
+		 * __must_check warning.
+		 */
 		return false;
 	}
 	if (!oldcrste.s.fc1.d && newcrste.s.fc1.d && !newcrste.s.fc1.s)
-- 
2.54.0