1 files changed, 22 insertions, 3 deletions

diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 040745b23224..9faaa8f96fc3 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -249,6 +249,25 @@ static inline int gisa_set_iam(struct kvm_s390_gisa *gisa, u8 iam)
         return 0;
 }
 
+/**
+ * gisa_clear_ipm - clear the GISA interruption pending mask
+ *
+ * @gisa: gisa to operate on
+ *
+ * Clear the IPM atomically with the next alert address and the IAM
+ * of the GISA unconditionally. All three fields are located in the
+ * first long word of the GISA.
+ */
+static inline void gisa_clear_ipm(struct kvm_s390_gisa *gisa)
+{
+        u64 word, _word;
+
+        do {
+                word = READ_ONCE(gisa->u64.word[0]);
+                _word = word & ~(0xffUL << 24);
+        } while (cmpxchg(&gisa->u64.word[0], word, _word) != word);
+}
+
 static inline void gisa_set_ipm_gisc(struct kvm_s390_gisa *gisa, u32 gisc)
 {
         set_bit_inv(IPM_BIT_OFFSET + gisc, (unsigned long *) gisa);
@@ -2926,8 +2945,7 @@ void kvm_s390_gisa_clear(struct kvm *kvm)
 
         if (!gi->origin)
                 return;
-        memset(gi->origin, 0, sizeof(struct kvm_s390_gisa));
-        gi->origin->next_alert = (u32)(u64)gi->origin;
+        gisa_clear_ipm(gi->origin);
         VM_EVENT(kvm, 3, "gisa 0x%pK cleared", gi->origin);
 }
 
@@ -2940,7 +2958,8 @@ void kvm_s390_gisa_init(struct kvm *kvm)
         gi->origin = &kvm->arch.sie_page2->gisa;
         gi->alert.mask = 0;
         spin_lock_init(&gi->alert.ref_lock);
-        kvm_s390_gisa_clear(kvm);
+        memset(gi->origin, 0, sizeof(struct kvm_s390_gisa));
+        gi->origin->next_alert = (u32)(u64)gi->origin;
         VM_EVENT(kvm, 3, "gisa 0x%pK initialized", gi->origin);
 }