diff --git a/xen/arch/x86/hvm/io.c b/xen/arch/x86/hvm/io.c
index 15e0b4c0ae..bf6309de26 100644
--- a/xen/arch/x86/hvm/io.c
+++ b/xen/arch/x86/hvm/io.c
@@ -300,7 +300,10 @@ void hvm_io_assist(ioreq_t *p)
     }
 
     if ( p->state == STATE_IOREQ_NONE )
+    {
+        msix_write_completion(curr);
         vcpu_end_shutdown_deferral(curr);
+    }
 }
 
 static int dpci_ioport_read(uint32_t mport, ioreq_t *p)
diff --git a/xen/arch/x86/hvm/vmsi.c b/xen/arch/x86/hvm/vmsi.c
index 4826b4ad77..10e5f34954 100644
--- a/xen/arch/x86/hvm/vmsi.c
+++ b/xen/arch/x86/hvm/vmsi.c
@@ -293,7 +293,11 @@ static int msixtbl_write(struct vcpu *v, unsigned long address,
 
     /* exit to device model if address/data has been modified */
     if ( test_and_clear_bit(nr_entry, &entry->table_flags) )
+    {
+        if ( !(val & PCI_MSIX_VECTOR_BITMASK) )
+            v->arch.hvm_vcpu.hvm_io.msix_unmask_address = address;
         goto out;
+    }
 
     virt = msixtbl_addr_to_virt(entry, address);
     if ( !virt )
@@ -528,3 +532,15 @@ void msixtbl_pt_cleanup(struct domain *d)
     spin_unlock(&d->arch.hvm_domain.msixtbl_list_lock);
     local_irq_restore(flags);
 }
+
+void msix_write_completion(struct vcpu *v)
+{
+    unsigned long ctrl_address = v->arch.hvm_vcpu.hvm_io.msix_unmask_address;
+
+    if ( !ctrl_address )
+        return;
+
+    v->arch.hvm_vcpu.hvm_io.msix_unmask_address = 0;
+    if ( msixtbl_write(v, ctrl_address, 4, 0) != X86EMUL_OKAY )
+        gdprintk(XENLOG_WARNING, "MSI-X write completion failure\n");
+}
diff --git a/xen/include/asm-x86/hvm/io.h b/xen/include/asm-x86/hvm/io.h
index 6f4cb96408..86db58de0a 100644
--- a/xen/include/asm-x86/hvm/io.h
+++ b/xen/include/asm-x86/hvm/io.h
@@ -124,6 +124,7 @@ void hvm_interrupt_post(struct vcpu *v, int vector, int type);
 void hvm_io_assist(ioreq_t *p);
 void hvm_dpci_eoi(struct domain *d, unsigned int guest_irq,
                   union vioapic_redir_entry *ent);
+void msix_write_completion(struct vcpu *);
 
 struct hvm_hw_stdvga {
     uint8_t sr_index;
diff --git a/xen/include/asm-x86/hvm/vcpu.h b/xen/include/asm-x86/hvm/vcpu.h
index a309389187..4f45060e7f 100644
--- a/xen/include/asm-x86/hvm/vcpu.h
+++ b/xen/include/asm-x86/hvm/vcpu.h
@@ -74,6 +74,8 @@ struct hvm_vcpu_io {
      * necessary retry through other than function return codes.
      */
     bool_t mmio_retry, mmio_retrying;
+
+    unsigned long msix_unmask_address;
 };
 
 #define VMCX_EADDR    (~0ULL)