Index: sys/dev/iommu/busdma_iommu.c
===================================================================
--- sys/dev/iommu/busdma_iommu.c
+++ sys/dev/iommu/busdma_iommu.c
@@ -619,8 +619,8 @@
 		if (buflen1 > tag->common.maxsegsz)
 			buflen1 = tag->common.maxsegsz;
 
-		KASSERT(((entry->start + offset) & (tag->common.alignment - 1))
-		    == 0,
+		KASSERT(vm_page_align_ok(entry->start + offset,
+		    tag->common.alignment),
 		    ("alignment failed: ctx %p start 0x%jx offset %x "
 		    "align 0x%jx", ctx, (uintmax_t)entry->start, offset,
 		    (uintmax_t)tag->common.alignment));
@@ -631,7 +631,7 @@
 		    (uintmax_t)entry->start, (uintmax_t)entry->end,
 		    (uintmax_t)tag->common.lowaddr,
 		    (uintmax_t)tag->common.highaddr));
-		KASSERT(iommu_test_boundary(entry->start + offset, buflen1,
+		KASSERT(vm_page_bound_ok(entry->start + offset, buflen1,
 		    tag->common.boundary),
 		    ("boundary failed: ctx %p start 0x%jx end 0x%jx "
 		    "boundary 0x%jx", ctx, (uintmax_t)entry->start,
Index: sys/dev/iommu/iommu.h
===================================================================
--- sys/dev/iommu/iommu.h
+++ sys/dev/iommu/iommu.h
@@ -148,16 +148,6 @@
 #define	IOMMU_DOMAIN_UNLOCK(dom)	mtx_unlock(&(dom)->lock)
 #define	IOMMU_DOMAIN_ASSERT_LOCKED(dom)	mtx_assert(&(dom)->lock, MA_OWNED)
 
-static inline bool
-iommu_test_boundary(iommu_gaddr_t start, iommu_gaddr_t size,
-    iommu_gaddr_t boundary)
-{
-
-	if (boundary == 0)
-		return (true);
-	return (start + size <= ((start + boundary) & ~(boundary - 1)));
-}
-
 void iommu_free_ctx(struct iommu_ctx *ctx);
 void iommu_free_ctx_locked(struct iommu_unit *iommu, struct iommu_ctx *ctx);
 struct iommu_ctx *iommu_get_ctx(struct iommu_unit *, device_t dev,
Index: sys/dev/iommu/iommu_gas.c
===================================================================
--- sys/dev/iommu/iommu_gas.c
+++ sys/dev/iommu/iommu_gas.c
@@ -314,7 +314,7 @@
 		return (false);
 
 	/* No boundary crossing. */
-	if (iommu_test_boundary(a->entry->start + a->offset, a->size,
+	if (vm_page_bound_ok(a->entry->start + a->offset, a->size,
 	    a->common->boundary))
 		return (true);
 
Index: sys/vm/vm_map.c
===================================================================
--- sys/vm/vm_map.c
+++ sys/vm/vm_map.c
@@ -2032,10 +2032,8 @@
 		 */
 		if (alignment == 0)
 			pmap_align_superpage(object, offset, addr, length);
-		else if ((*addr & (alignment - 1)) != 0) {
-			*addr &= ~(alignment - 1);
-			*addr += alignment;
-		}
+		else
+			*addr = roundup2(*addr, alignment);
 		aligned_addr = *addr;
 		if (aligned_addr == free_addr) {
 			/*
Index: sys/vm/vm_page.h
===================================================================
--- sys/vm/vm_page.h
+++ sys/vm/vm_page.h
@@ -1017,5 +1017,24 @@
 #endif
 }
 
+static inline bool
+vm_page_align_ok(vm_paddr_t pa, u_long alignment)
+{
+	return ((pa & (alignment - 1)) == 0);
+}
+
+static inline bool
+vm_page_bound_ok(vm_paddr_t pa, vm_paddr_t size, vm_paddr_t boundary)
+{
+	return (((pa ^ (pa + size - 1)) & -boundary) == 0);
+}
+
+static inline bool
+vm_page_addr_ok(vm_paddr_t pa, vm_paddr_t size, u_long alignment,
+    vm_paddr_t boundary)
+{
+	return (vm_page_align_ok(pa, alignment) &&
+	    vm_page_bound_ok(pa, size, boundary));
+}
 #endif				/* _KERNEL */
 #endif				/* !_VM_PAGE_ */
Index: sys/vm/vm_page.c
===================================================================
--- sys/vm/vm_page.c
+++ sys/vm/vm_page.c
@@ -2656,12 +2656,11 @@
 			if (m + npages > m_end)
 				break;
 			pa = VM_PAGE_TO_PHYS(m);
-			if ((pa & (alignment - 1)) != 0) {
+			if (!vm_page_align_ok(pa, alignment)) {
 				m_inc = atop(roundup2(pa, alignment) - pa);
 				continue;
 			}
-			if (rounddown2(pa ^ (pa + ptoa(npages) - 1),
-			    boundary) != 0) {
+			if (!vm_page_bound_ok(pa, ptoa(npages), boundary)) {
 				m_inc = atop(roundup2(pa, boundary) - pa);
 				continue;
 			}
Index: sys/vm/vm_phys.c
===================================================================
--- sys/vm/vm_phys.c
+++ sys/vm/vm_phys.c
@@ -1466,8 +1466,8 @@
 				pa = VM_PAGE_TO_PHYS(m_ret);
 				pa_end = pa + size;
 				if (pa >= low && pa_end <= high &&
-				    (pa & (alignment - 1)) == 0 &&
-				    rounddown2(pa ^ (pa_end - 1), boundary) == 0)
+				    vm_page_addr_ok(pa, size,
+				    alignment, boundary))
 					goto done;
 			}
 		}
Index: sys/vm/vm_reserv.c
===================================================================
--- sys/vm/vm_reserv.c
+++ sys/vm/vm_reserv.c
@@ -656,10 +656,8 @@
 	 * possible size satisfy the alignment and boundary requirements?
 	 */
 	pa = VM_RESERV_INDEX(object, pindex) << PAGE_SHIFT;
-	if ((pa & (alignment - 1)) != 0)
-		return (NULL);
 	size = npages << PAGE_SHIFT;
-	if (((pa ^ (pa + size - 1)) & ~(boundary - 1)) != 0)
+	if (!vm_page_addr_ok(pa, size, alignment, boundary))
 		return (NULL);
 
 	/*
@@ -682,8 +680,7 @@
 		m = &rv->pages[index];
 		pa = VM_PAGE_TO_PHYS(m);
 		if (pa < low || pa + size > high ||
-		    (pa & (alignment - 1)) != 0 ||
-		    ((pa ^ (pa + size - 1)) & ~(boundary - 1)) != 0)
+		    !vm_page_addr_ok(pa, size, alignment, boundary))
 			goto out;
 		/* Handle vm_page_rename(m, new_object, ...). */
 		for (i = 0; i < npages; i++)
@@ -1333,7 +1330,7 @@
 	 * doesn't include a boundary-multiple within it.  Otherwise,
 	 * no boundary-constrained allocation is possible.
 	 */
-	if (size > boundary && boundary > 0)
+	if (boundary != 0 && !vm_page_bound_ok(0, size, boundary))
 		return (NULL);
 	marker = &vm_rvd[domain].marker;
 	queue = &vm_rvd[domain].partpop;
@@ -1360,7 +1357,7 @@
 			/* This entire reservation is too high; go to next. */
 			continue;
 		}
-		if ((pa & (alignment - 1)) != 0) {
+		if (!vm_page_align_ok(pa, alignment)) {
 			/* This entire reservation is unaligned; go to next. */
 			continue;
 		}
@@ -1397,12 +1394,10 @@
 			vm_reserv_unlock(rv);
 			m_ret = &rv->pages[posn];
 			pa = VM_PAGE_TO_PHYS(m_ret);
-			KASSERT((pa & (alignment - 1)) == 0,
-			    ("%s: adjusted address does not align to %lx",
-			    __func__, alignment));
-			KASSERT(((pa ^ (pa + size - 1)) & -boundary) == 0,
-			    ("%s: adjusted address spans boundary to %jx",
-			    __func__, (uintmax_t)boundary));
+			KASSERT(vm_page_addr_ok(pa, size, alignment, boundary),
+			    ("%s: adjusted address not aligned/bounded to "
+			     "%lx/%jx",
+			     __func__, alignment, (uintmax_t)boundary));
 			return (m_ret);
 		}
 		vm_reserv_domain_lock(domain);