diff -urN zfs-0.8.4/config/kernel-kmem.m4 zfs-0.8.4-5.8/config/kernel-kmem.m4
--- zfs-0.8.4/config/kernel-kmem.m4	1970-01-01 01:00:00.000000000 +0100
+++ zfs-0.8.4-5.8/config/kernel-kmem.m4	2020-08-16 20:47:36.079945075 +0200
@@ -0,0 +1,24 @@
+dnl #
+dnl # 5.8 API,
+dnl # __vmalloc PAGE_KERNEL removal
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_SRC_VMALLOC_PAGE_KERNEL], [
+	ZFS_LINUX_TEST_SRC([__vmalloc], [
+		#include <linux/mm.h>
+		#include <linux/vmalloc.h>
+	],[
+		void *p __attribute__ ((unused));
+
+		p = __vmalloc(0, GFP_KERNEL, PAGE_KERNEL);
+	])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_VMALLOC_PAGE_KERNEL], [
+	AC_MSG_CHECKING([whether __vmalloc(ptr, flags, pageflags) is available])
+	ZFS_LINUX_TEST_RESULT([__vmalloc], [
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_VMALLOC_PAGE_KERNEL, 1, [__vmalloc page flags exists])
+	],[
+		AC_MSG_RESULT(no)
+	])
+])
diff -ur zfs-0.8.4/aclocal.m4 zfs-0.8.4-5.8/aclocal.m4
--- zfs-0.8.4/aclocal.m4	2020-05-05 18:56:50.832844255 +0200
+++ zfs-0.8.4-5.8/aclocal.m4	2020-08-16 20:47:51.756613733 +0200
@@ -1503,6 +1503,7 @@
 m4_include([config/kernel-invalidate-bdev-args.m4])
 m4_include([config/kernel-is_owner_or_cap.m4])
 m4_include([config/kernel-kmap-atomic-args.m4])
+m4_include([config/kernel-kmem.m4])
 m4_include([config/kernel-kmem-cache.m4])
 m4_include([config/kernel-kstrtoul.m4])
 m4_include([config/kernel-ktime.m4])
diff -ur zfs-0.8.4/config/kernel.m4 zfs-0.8.4-5.8/config/kernel.m4
--- zfs-0.8.4/config/kernel.m4	2020-08-16 20:52:32.199984184 +0200
+++ zfs-0.8.4-5.8/config/kernel.m4	2020-08-16 20:48:47.436620888 +0200
@@ -45,6 +45,7 @@
 	ZFS_AC_KERNEL_SRC_SCHED
 	ZFS_AC_KERNEL_SRC_USLEEP_RANGE
 	ZFS_AC_KERNEL_SRC_KMEM_CACHE
+	ZFS_AC_KERNEL_SRC_VMALLOC_PAGE_KERNEL
 	ZFS_AC_KERNEL_SRC_WAIT
 	ZFS_AC_KERNEL_SRC_INODE_TIMES
 	ZFS_AC_KERNEL_SRC_INODE_LOCK
@@ -163,6 +164,7 @@
 	ZFS_AC_KERNEL_SCHED
 	ZFS_AC_KERNEL_USLEEP_RANGE
 	ZFS_AC_KERNEL_KMEM_CACHE
+	ZFS_AC_KERNEL_VMALLOC_PAGE_KERNEL
 	ZFS_AC_KERNEL_WAIT
 	ZFS_AC_KERNEL_INODE_TIMES
 	ZFS_AC_KERNEL_INODE_LOCK
diff -ur zfs-0.8.4/include/spl/sys/kmem.h zfs-0.8.4-5.8/include/spl/sys/kmem.h
--- zfs-0.8.4/include/spl/sys/kmem.h	2020-05-05 18:56:29.717370676 +0200
+++ zfs-0.8.4-5.8/include/spl/sys/kmem.h	2020-08-16 20:49:25.949959237 +0200
@@ -170,6 +170,15 @@
 extern void spl_kmem_free(const void *ptr, size_t sz);
 
 /*
+ * 5.8 API change, pgprot_t argument removed.
+ */
+#ifdef HAVE_VMALLOC_PAGE_KERNEL
+#define	spl_vmalloc(size, flags)	__vmalloc(size, flags, PAGE_KERNEL)
+#else
+#define	spl_vmalloc(size, flags)	__vmalloc(size, flags)
+#endif
+
+/*
  * The following functions are only available for internal use.
  */
 extern void *spl_kmem_alloc_impl(size_t size, int flags, int node);
diff -ur zfs-0.8.4/module/spl/spl-kmem.c zfs-0.8.4-5.8/module/spl/spl-kmem.c
--- zfs-0.8.4/module/spl/spl-kmem.c	2020-05-05 18:57:28.442960922 +0200
+++ zfs-0.8.4-5.8/module/spl/spl-kmem.c	2020-08-16 20:52:08.019980890 +0200
@@ -172,16 +171,15 @@
 		 * kmem_zalloc() callers.
 		 *
 		 * For vmem_alloc() and vmem_zalloc() callers it is permissible
-		 * to use __vmalloc().  However, in general use of __vmalloc()
-		 * is strongly discouraged because a global lock must be
-		 * acquired.  Contention on this lock can significantly
+		 * to use spl_vmalloc().  However, in general use of
+		 * spl_vmalloc() is strongly discouraged because a global lock
+		 * must be acquired.  Contention on this lock can significantly
 		 * impact performance so frequently manipulating the virtual
 		 * address space is strongly discouraged.
 		 */
 		if ((size > spl_kmem_alloc_max) || use_vmem) {
 			if (flags & KM_VMEM) {
-				ptr = __vmalloc(size, lflags | __GFP_HIGHMEM,
-				    PAGE_KERNEL);
+				ptr = spl_vmalloc(size, lflags | __GFP_HIGHMEM);
 			} else {
 				return (NULL);
 			}
diff -ur zfs-0.8.4/module/spl/spl-kmem-cache.c zfs-0.8.4-5.8/module/spl/spl-kmem-cache.c
--- zfs-0.8.4/module/spl/spl-kmem-cache.c	2020-05-05 18:57:28.442960922 +0200
+++ zfs-0.8.4-5.8/module/spl/spl-kmem-cache.c	2020-08-16 20:50:28.763300871 +0200
@@ -203,7 +203,7 @@
 		ASSERT(ISP2(size));
 		ptr = (void *)__get_free_pages(lflags, get_order(size));
 	} else {
-		ptr = __vmalloc(size, lflags | __GFP_HIGHMEM, PAGE_KERNEL);
+		ptr = spl_vmalloc(size, lflags | __GFP_HIGHMEM);
 	}
 
 	/* Resulting allocated memory will be page aligned */
@@ -1242,7 +1242,7 @@
 	 * allocation.
 	 *
 	 * However, this can't be applied to KVM_VMEM due to a bug that
-	 * __vmalloc() doesn't honor gfp flags in page table allocation.
+	 * spl_vmalloc() doesn't honor gfp flags in page table allocation.
 	 */
 	if (!(skc->skc_flags & KMC_VMEM)) {
 		rc = __spl_cache_grow(skc, flags | KM_NOSLEEP);