diff --git a/sys/compat/linuxkpi/common/include/linux/vmalloc.h b/sys/compat/linuxkpi/common/include/linux/vmalloc.h
--- a/sys/compat/linuxkpi/common/include/linux/vmalloc.h
+++ b/sys/compat/linuxkpi/common/include/linux/vmalloc.h
@@ -35,8 +35,11 @@
 #define	VM_MAP		0x0000
 #define	PAGE_KERNEL	0x0000
 
+#define	vmap_pfn(...)	linuxkpi_vmap_pfn(__VA_ARGS__)
+
 void *vmap(struct page **pages, unsigned int count, unsigned long flags,
     int prot);
+void *linuxkpi_vmap_pfn(unsigned long *pfns, unsigned int count, int prot);
 void vunmap(void *addr);
 
 #endif	/* _LINUXKPI_LINUX_VMALLOC_H_ */
diff --git a/sys/compat/linuxkpi/common/src/linux_page.c b/sys/compat/linuxkpi/common/src/linux_page.c
--- a/sys/compat/linuxkpi/common/src/linux_page.c
+++ b/sys/compat/linuxkpi/common/src/linux_page.c
@@ -342,6 +342,16 @@
 int
 is_vmalloc_addr(const void *addr)
 {
+	struct vmmap *vmmap;
+
+	mtx_lock(&vmmaplock);
+	LIST_FOREACH(vmmap, &vmmaphead[VM_HASH(addr)], vm_next)
+		if (addr == vmmap->vm_addr)
+			break;
+	mtx_unlock(&vmmaplock);
+	if (vmmap != NULL)
+		return(1);
+
 	return (vtoslab((vm_offset_t)addr & ~UMA_SLAB_MASK) != NULL);
 }
 
@@ -431,6 +441,28 @@
 	return ((void *)off);
 }
 
+void *
+linuxkpi_vmap_pfn(unsigned long *pfns, unsigned int count, int prot)
+{
+#ifdef __amd64__
+	vm_offset_t off;
+	size_t size;
+
+	size = count * PAGE_SIZE;
+	off = kva_alloc(size);
+	if (off == 0)
+		return (NULL);
+	vmmap_add((void *)off, size, true);
+	pmap_qmapdev_attr(off, pfns, count, pgprot2cachemode(prot));
+
+	return ((void *)off);
+#else
+	/* vmap_pfn() is currently used only by i915kms */
+	panic("pmap_qmapdev_attr is not implemented on %s", MACHINE);
+	return (NULL);
+#endif
+}
+
 void
 vunmap(void *addr)
 {