Index: head/sys/x86/iommu/intel_ctx.c
===================================================================
--- head/sys/x86/iommu/intel_ctx.c
+++ head/sys/x86/iommu/intel_ctx.c
@@ -117,7 +117,7 @@
 	struct dmar_unit *dmar;
 	dmar_ctx_entry_t *ctxp;
 
-	dmar = (struct dmar_unit *)ctx->context.domain->iommu;
+	dmar = CTX2DMAR(ctx);
 
 	ctxp = dmar_map_pgtbl(dmar->ctx_obj, 1 +
 	    PCI_RID2BUS(ctx->rid), IOMMU_PGF_NOALLOC | IOMMU_PGF_WAITOK, sfp);
@@ -131,7 +131,7 @@
 	struct dmar_domain *domain;
 	bus_addr_t maxaddr;
 
-	domain = (struct dmar_domain *)ctx->context.domain;
+	domain = CTX2DOM(ctx);
 	maxaddr = MIN(domain->iodom.end, BUS_SPACE_MAXADDR);
 	ctx->context.tag->common.ref_count = 1; /* Prevent free */
 	ctx->context.tag->common.impl = &bus_dma_iommu_impl;
@@ -141,7 +141,7 @@
 	ctx->context.tag->common.maxsize = maxaddr;
 	ctx->context.tag->common.nsegments = BUS_SPACE_UNRESTRICTED;
 	ctx->context.tag->common.maxsegsz = maxaddr;
-	ctx->context.tag->ctx = (struct iommu_ctx *)ctx;
+	ctx->context.tag->ctx = CTX2IOCTX(ctx);
 	ctx->context.tag->owner = dev;
 }
 
@@ -178,8 +178,8 @@
 	vm_page_t ctx_root;
 	int i;
 
-	domain = (struct dmar_domain *)ctx->context.domain;
-	unit = (struct dmar_unit *)domain->iodom.iommu;
+	domain = CTX2DOM(ctx);
+	unit = DOM2DMAR(domain);
 	KASSERT(move || (ctxp->ctx1 == 0 && ctxp->ctx2 == 0),
 	    ("dmar%d: initialized ctx entry %d:%d:%d 0x%jx 0x%jx",
 	    unit->iommu.unit, busno, pci_get_slot(ctx->context.tag->owner),
@@ -196,7 +196,7 @@
 		    IOMMU_PGF_NOALLOC);
 	}
 
-	if (iommu_is_buswide_ctx((struct iommu_unit *)unit, busno)) {
+	if (iommu_is_buswide_ctx(DMAR2IOMMU(unit), busno)) {
 		MPASS(!move);
 		for (i = 0; i <= PCI_BUSMAX; i++) {
 			ctx_id_entry_init_one(&ctxp[i], domain, ctx_root);
@@ -283,8 +283,7 @@
 			ma[i] = vm_page_getfake(entry->start + PAGE_SIZE * i,
 			    VM_MEMATTR_DEFAULT);
 		}
-		error1 = iommu_gas_map_region((struct iommu_domain *)domain,
-		    entry,
+		error1 = iommu_gas_map_region(DOM2IODOM(domain), entry,
 		    IOMMU_MAP_ENTRY_READ | IOMMU_MAP_ENTRY_WRITE,
 		    IOMMU_MF_CANWAIT | IOMMU_MF_RMRR, ma);
 		/*
@@ -310,8 +309,7 @@
 				error = error1;
 			}
 			TAILQ_REMOVE(&rmrr_entries, entry, unroll_link);
-			iommu_gas_free_entry((struct iommu_domain *)domain,
-			    entry);
+			iommu_gas_free_entry(DOM2IODOM(domain), entry);
 		}
 		for (i = 0; i < size; i++)
 			vm_page_putfake(ma[i]);
@@ -331,7 +329,7 @@
 	if (id == -1)
 		return (NULL);
 	domain = malloc(sizeof(*domain), M_DMAR_DOMAIN, M_WAITOK | M_ZERO);
-	iodom = (struct iommu_domain *)domain;
+	iodom = DOM2IODOM(domain);
 	domain->domain = id;
 	LIST_INIT(&domain->contexts);
 	RB_INIT(&domain->iodom.rb_root);
@@ -358,7 +356,7 @@
 		/* Use all supported address space for remapping. */
 		domain->iodom.end = 1ULL << (domain->agaw - 1);
 
-	iommu_gas_init_domain((struct iommu_domain *)domain);
+	iommu_gas_init_domain(DOM2IODOM(domain));
 
 	if (id_mapped) {
 		if ((dmar->hw_ecap & DMAR_ECAP_PT) == 0) {
@@ -389,7 +387,7 @@
 	struct dmar_ctx *ctx;
 
 	ctx = malloc(sizeof(*ctx), M_DMAR_CTX, M_WAITOK | M_ZERO);
-	ctx->context.domain = (struct iommu_domain *)domain;
+	ctx->context.domain = DOM2IODOM(domain);
 	ctx->context.tag = malloc(sizeof(struct bus_dma_tag_iommu),
 	    M_DMAR_CTX, M_WAITOK | M_ZERO);
 	ctx->rid = rid;
@@ -402,7 +400,7 @@
 {
 	struct dmar_domain *domain;
 
-	domain = (struct dmar_domain *)ctx->context.domain;
+	domain = CTX2DOM(ctx);
 	IOMMU_ASSERT_LOCKED(domain->iodom.iommu);
 	KASSERT(domain->refs >= domain->ctx_cnt,
 	    ("dom %p ref underflow %d %d", domain, domain->refs,
@@ -417,7 +415,7 @@
 {
 	struct dmar_domain *domain;
 
-	domain = (struct dmar_domain *)ctx->context.domain;
+	domain = CTX2DOM(ctx);
 	IOMMU_ASSERT_LOCKED(domain->iodom.iommu);
 	KASSERT(domain->refs > 0,
 	    ("domain %p ctx dtr refs %d", domain, domain->refs));
@@ -444,7 +442,7 @@
 	    ("destroying dom %p with refs %d", domain, domain->refs));
 	if ((domain->iodom.flags & IOMMU_DOMAIN_GAS_INITED) != 0) {
 		DMAR_DOMAIN_LOCK(domain);
-		iommu_gas_fini_domain((struct iommu_domain *)domain);
+		iommu_gas_fini_domain(DOM2IODOM(domain));
 		DMAR_DOMAIN_UNLOCK(domain);
 	}
 	if ((domain->iodom.flags & IOMMU_DOMAIN_PGTBL_INITED) != 0) {
@@ -453,7 +451,7 @@
 		domain_free_pgtbl(domain);
 	}
 	mtx_destroy(&domain->iodom.lock);
-	dmar = (struct dmar_unit *)domain->iodom.iommu;
+	dmar = DOM2DMAR(domain);
 	free_unr(dmar->domids, domain->domain);
 	free(domain, M_DMAR_DOMAIN);
 }
@@ -482,7 +480,7 @@
 	}
 	enable = false;
 	TD_PREP_PINNED_ASSERT;
-	unit = (struct iommu_unit *)dmar;
+	unit = DMAR2IOMMU(dmar);
 	DMAR_LOCK(dmar);
 	KASSERT(!iommu_is_buswide_ctx(unit, bus) || (slot == 0 && func == 0),
 	    ("iommu%d pci%d:%d:%d get_ctx for buswide", dmar->iommu.unit, bus,
@@ -550,11 +548,11 @@
 			dmar_domain_destroy(domain1);
 			/* Nothing needs to be done to destroy ctx1. */
 			free(ctx1, M_DMAR_CTX);
-			domain = (struct dmar_domain *)ctx->context.domain;
+			domain = CTX2DOM(ctx);
 			ctx->refs++; /* tag referenced us */
 		}
 	} else {
-		domain = (struct dmar_domain *)ctx->context.domain;
+		domain = CTX2DOM(ctx);
 		if (ctx->context.tag->owner == NULL)
 			ctx->context.tag->owner = dev;
 		ctx->refs++; /* tag referenced us */
@@ -627,7 +625,7 @@
 	int error;
 
 	dmar = domain->dmar;
-	old_domain = (struct dmar_domain *)ctx->context.domain;
+	old_domain = CTX2DOM(ctx);
 	if (domain == old_domain)
 		return (0);
 	KASSERT(old_domain->iodom.iommu == domain->iodom.iommu,
@@ -748,7 +746,7 @@
 			dmar_inv_iotlb_glob(dmar);
 	}
 	dmar_unmap_pgtbl(sf);
-	domain = (struct dmar_domain *)ctx->context.domain;
+	domain = CTX2DOM(ctx);
 	dmar_ctx_unlink(ctx);
 	free(ctx->context.tag, M_DMAR_CTX);
 	free(ctx, M_DMAR_CTX);
@@ -761,7 +759,7 @@
 {
 	struct dmar_unit *dmar;
 
-	dmar = (struct dmar_unit *)ctx->context.domain->iommu;
+	dmar = CTX2DMAR(ctx);
 	DMAR_LOCK(dmar);
 	dmar_free_ctx_locked(dmar, ctx);
 }
@@ -810,11 +808,11 @@
 	struct dmar_domain *domain;
 	struct dmar_unit *unit;
 
-	domain = (struct dmar_domain *)entry->domain;
-	unit = (struct dmar_unit *)domain->iodom.iommu;
+	domain = IODOM2DOM(entry->domain);
+	unit = DOM2DMAR(domain);
 	if (unit->qi_enabled) {
 		DMAR_LOCK(unit);
-		dmar_qi_invalidate_locked((struct dmar_domain *)entry->domain,
+		dmar_qi_invalidate_locked(IODOM2DOM(entry->domain),
 		    entry->start, entry->end - entry->start, &entry->gseq,
 		    true);
 		if (!free)
@@ -822,7 +820,7 @@
 		TAILQ_INSERT_TAIL(&unit->tlb_flush_entries, entry, dmamap_link);
 		DMAR_UNLOCK(unit);
 	} else {
-		domain_flush_iotlb_sync((struct dmar_domain *)entry->domain,
+		domain_flush_iotlb_sync(IODOM2DOM(entry->domain),
 		    entry->start, entry->end - entry->start);
 		dmar_domain_free_entry(entry, free);
 	}
@@ -847,8 +845,8 @@
 	struct iommu_map_entry *entry, *entry1;
 	int error;
 
-	iodom = (struct iommu_domain *)domain;
-	unit = (struct dmar_unit *)domain->iodom.iommu;
+	iodom = DOM2IODOM(domain);
+	unit = DOM2DMAR(domain);
 
 	TAILQ_FOREACH_SAFE(entry, entries, dmamap_link, entry1) {
 		KASSERT((entry->flags & IOMMU_MAP_ENTRY_MAP) != 0,
@@ -904,11 +902,11 @@
 	struct dmar_unit *dmar;
 	struct dmar_ctx *ret;
 
-	dmar = (struct dmar_unit *)iommu;
+	dmar = IOMMU2DMAR(iommu);
 
 	ret = dmar_get_ctx_for_dev(dmar, dev, rid, id_mapped, rmrr_init);
 
-	return ((struct iommu_ctx *)ret);
+	return (CTX2IOCTX(ret));
 }
 
 void
@@ -917,8 +915,8 @@
 	struct dmar_unit *dmar;
 	struct dmar_ctx *ctx;
 
-	dmar = (struct dmar_unit *)iommu;
-	ctx = (struct dmar_ctx *)context;
+	dmar = IOMMU2DMAR(iommu);
+	ctx = IOCTX2CTX(context);
 
 	dmar_free_ctx_locked(dmar, ctx);
 }
@@ -926,11 +924,9 @@
 void
 iommu_free_ctx(struct iommu_ctx *context)
 {
-	struct dmar_unit *dmar;
 	struct dmar_ctx *ctx;
 
-	ctx = (struct dmar_ctx *)context;
-	dmar = (struct dmar_unit *)ctx->context.domain->iommu;
+	ctx = IOCTX2CTX(context);
 
 	dmar_free_ctx(ctx);
 }
@@ -948,7 +944,7 @@
 {
 	struct dmar_domain *domain;
 
-	domain = (struct dmar_domain *)iodom;
+	domain = IODOM2DOM(iodom);
 
 	dmar_domain_unload(domain, entries, cansleep);
 }
Index: head/sys/x86/iommu/intel_dmar.h
===================================================================
--- head/sys/x86/iommu/intel_dmar.h
+++ head/sys/x86/iommu/intel_dmar.h
@@ -91,6 +91,22 @@
 #define	DMAR_DOMAIN_UNLOCK(dom)	mtx_unlock(&(dom)->iodom.lock)
 #define	DMAR_DOMAIN_ASSERT_LOCKED(dom) mtx_assert(&(dom)->iodom.lock, MA_OWNED)
 
+#define	DMAR2IOMMU(dmar)	&((dmar)->iommu)
+#define	IOMMU2DMAR(dmar)	\
+	__containerof((dmar), struct dmar_unit, iommu)
+
+#define	DOM2IODOM(domain)	&((domain)->iodom)
+#define	IODOM2DOM(domain)	\
+	__containerof((domain), struct dmar_domain, iodom)
+
+#define	CTX2IOCTX(ctx)		&((ctx)->context)
+#define	IOCTX2CTX(ctx)		\
+	__containerof((ctx), struct dmar_ctx, context)
+
+#define	CTX2DOM(ctx)		IODOM2DOM((ctx)->context.domain)
+#define	CTX2DMAR(ctx)		(CTX2DOM(ctx)->dmar)
+#define	DOM2DMAR(domain)	((domain)->dmar)
+
 struct dmar_msi_data {
 	int irq;
 	int irq_rid;
Index: head/sys/x86/iommu/intel_drv.c
===================================================================
--- head/sys/x86/iommu/intel_drv.c
+++ head/sys/x86/iommu/intel_drv.c
@@ -919,8 +919,7 @@
 		match = dmar_match_devscope(devscope, ria->dev_busno,
 		    ria->dev_path, ria->dev_path_len);
 		if (match == 1) {
-			entry = iommu_gas_alloc_entry(
-			    (struct iommu_domain *)ria->domain,
+			entry = iommu_gas_alloc_entry(DOM2IODOM(ria->domain),
 			    IOMMU_PGF_WAITOK);
 			entry->start = resmem->BaseAddress;
 			/* The RMRR entry end address is inclusive. */
@@ -1056,7 +1055,7 @@
 	struct inst_rmrr_iter_args iria;
 	int error;
 
-	dmar = (struct dmar_unit *)unit;
+	dmar = IOMMU2DMAR(unit);
 
 	if (!dmar_barrier_enter(dmar, DMAR_BARRIER_RMRR))
 		return (0);
@@ -1131,7 +1130,7 @@
 	struct iommu_map_entry *entry;
 	struct dmar_ctx *ctx;
 
-	iodom = (struct iommu_domain *)domain;
+	iodom = DOM2IODOM(domain);
 
 	db_printf(
 	    "  @%p dom %d mgaw %d agaw %d pglvl %d end %jx refs %d\n"
Index: head/sys/x86/iommu/intel_idpgtbl.c
===================================================================
--- head/sys/x86/iommu/intel_idpgtbl.c
+++ head/sys/x86/iommu/intel_idpgtbl.c
@@ -512,7 +512,7 @@
 	    ((eflags & IOMMU_MAP_ENTRY_SNOOP) != 0 ? DMAR_PTE_SNP : 0) |
 	    ((eflags & IOMMU_MAP_ENTRY_TM) != 0 ? DMAR_PTE_TM : 0);
 
-	domain = (struct dmar_domain *)iodom;
+	domain = IODOM2DOM(iodom);
 	unit = domain->dmar;
 
 	KASSERT((domain->iodom.flags & IOMMU_DOMAIN_IDMAP) == 0,
@@ -691,7 +691,7 @@
 	struct dmar_domain *domain;
 	int error;
 
-	domain = (struct dmar_domain *)iodom;
+	domain = IODOM2DOM(iodom);
 
 	DMAR_DOMAIN_PGLOCK(domain);
 	error = domain_unmap_buf_locked(domain, base, size, flags);
@@ -823,6 +823,6 @@
 {
 	struct iommu_domain *iodom;
 
-	iodom = (struct iommu_domain *)domain;
+	iodom = DOM2IODOM(domain);
 	iodom->ops = &dmar_domain_map_ops;
 }
Index: head/sys/x86/iommu/intel_quirks.c
===================================================================
--- head/sys/x86/iommu/intel_quirks.c
+++ head/sys/x86/iommu/intel_quirks.c
@@ -226,7 +226,7 @@
 {
 	struct dmar_unit *dmar;
 
-	dmar = (struct dmar_unit *)unit;
+	dmar = IOMMU2DMAR(unit);
 
 	if (!dmar_barrier_enter(dmar, DMAR_BARRIER_USEQ))
 		return;