Index: sys/dev/pci/pci.c
===================================================================
--- sys/dev/pci/pci.c
+++ sys/dev/pci/pci.c
@@ -1671,10 +1671,12 @@
 	KASSERT(msix->msix_msgnum > index, ("bogus index"));
 	offset = msix->msix_table_offset + index * 16 + 12;
 	val = bus_read_4(msix->msix_table_res, offset);
-	if (!(val & PCIM_MSIX_VCTRL_MASK)) {
-		val |= PCIM_MSIX_VCTRL_MASK;
-		bus_write_4(msix->msix_table_res, offset, val);
-	}
+	val |= PCIM_MSIX_VCTRL_MASK;
+	/*
+	 * Some devices (eg Samsung PM961) cannot handle RMW on this register for
+	 * all its vectors, so write the values we need directly.
+	 */
+	bus_write_4(msix->msix_table_res, offset, PCIM_MSIX_VCTRL_MASK);
 }
 
 void
@@ -1687,10 +1689,12 @@
 	KASSERT(msix->msix_table_len > index, ("bogus index"));
 	offset = msix->msix_table_offset + index * 16 + 12;
 	val = bus_read_4(msix->msix_table_res, offset);
-	if (val & PCIM_MSIX_VCTRL_MASK) {
-		val &= ~PCIM_MSIX_VCTRL_MASK;
-		bus_write_4(msix->msix_table_res, offset, val);
-	}
+	val &= ~PCIM_MSIX_VCTRL_MASK;
+	/*
+	 * Some devices (eg Samsung PM961) cannot handle RMW on this register for
+	 * all its vectors, so write the values we need directly.
+	 */
+	bus_write_4(msix->msix_table_res, offset, 0);
 }
 
 int