+ s390-mm-implement-mem_prepare_online-mem_finish_offline-notifiers.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: s390/mm: implement MEM_PREPARE_ONLINE/MEM_FINISH_OFFLINE notifiers
has been added to the -mm mm-unstable branch.  Its filename is
     s390-mm-implement-mem_prepare_online-mem_finish_offline-notifiers.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/s390-mm-implement-mem_prepare_online-mem_finish_offline-notifiers.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Sumanth Korikkar <sumanthk@linux.ibm.com>
Subject: s390/mm: implement MEM_PREPARE_ONLINE/MEM_FINISH_OFFLINE notifiers
Date: Tue, 28 Nov 2023 16:52:26 +0100

MEM_PREPARE_ONLINE memory notifier makes memory block physical accessible
via sclp assign command.  The notifier ensures self-contained memory maps
are accessible and hence enabling the "memmap on memory" on s390.

MEM_FINISH_OFFLINE memory notifier shifts the memory block to an
inaccessible state via sclp unassign command.

Implementation considerations:
* When MHP_MEMMAP_ON_MEMORY is disabled, the system retains the old
  behavior. This means the memory map is allocated from default memory.
* If MACHINE_HAS_EDAT1 is unavailable, MHP_MEMMAP_ON_MEMORY is
  automatically disabled. This ensures that vmemmap pagetables do not
  consume additional memory from the default memory allocator.
* The MEM_GOING_ONLINE notifier has been modified to perform no
  operation, as MEM_PREPARE_ONLINE already executes the sclp assign
  command.
* The MEM_CANCEL_ONLINE/MEM_OFFLINE notifier now performs no operation, as
  MEM_FINISH_OFFLINE already executes the sclp unassign command.

Link: https://lkml.kernel.org/r/20231128155227.1315063-5-sumanthk@linux.ibm.com
Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Reviewed-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/s390/char/sclp_cmd.c |   41 ++++++++++++++++++++++++++++-----
 1 file changed, 35 insertions(+), 6 deletions(-)

--- a/drivers/s390/char/sclp_cmd.c~s390-mm-implement-mem_prepare_online-mem_finish_offline-notifiers
+++ a/drivers/s390/char/sclp_cmd.c
@@ -18,6 +18,7 @@
 #include <linux/mm.h>
 #include <linux/mmzone.h>
 #include <linux/memory.h>
+#include <linux/memory_hotplug.h>
 #include <linux/module.h>
 #include <asm/ctlreg.h>
 #include <asm/chpid.h>
@@ -26,6 +27,7 @@
 #include <asm/sclp.h>
 #include <asm/numa.h>
 #include <asm/facility.h>
+#include <asm/page-states.h>
 
 #include "sclp.h"
 
@@ -340,13 +342,38 @@ static int sclp_mem_notifier(struct noti
 		if (contains_standby_increment(start, start + size))
 			rc = -EPERM;
 		break;
-	case MEM_GOING_ONLINE:
+	case MEM_PREPARE_ONLINE:
+		/*
+		 * Access the altmap_start_pfn and altmap_nr_pages fields
+		 * within the struct memory_notify specifically when dealing
+		 * with only MEM_PREPARE_ONLINE/MEM_FINISH_OFFLINE notifiers.
+		 *
+		 * When altmap is in use, take the specified memory range
+		 * online, which includes the altmap.
+		 */
+		if (arg->altmap_nr_pages) {
+			start = PFN_PHYS(arg->altmap_start_pfn);
+			size += PFN_PHYS(arg->altmap_nr_pages);
+		}
 		rc = sclp_mem_change_state(start, size, 1);
+		if (rc || !arg->altmap_nr_pages)
+			break;
+		/*
+		 * Set CMMA state to nodat here, since the struct page memory
+		 * at the beginning of the memory block will not go through the
+		 * buddy allocator later.
+		 */
+		__arch_set_page_nodat((void *)__va(start), arg->altmap_nr_pages);
 		break;
-	case MEM_CANCEL_ONLINE:
-		sclp_mem_change_state(start, size, 0);
-		break;
-	case MEM_OFFLINE:
+	case MEM_FINISH_OFFLINE:
+		/*
+		 * When altmap is in use, take the specified memory range
+		 * offline, which includes the altmap.
+		 */
+		if (arg->altmap_nr_pages) {
+			start = PFN_PHYS(arg->altmap_start_pfn);
+			size += PFN_PHYS(arg->altmap_nr_pages);
+		}
 		sclp_mem_change_state(start, size, 0);
 		break;
 	default:
@@ -397,7 +424,9 @@ static void __init add_memory_merged(u16
 	if (!size)
 		goto skip_add;
 	for (addr = start; addr < start + size; addr += block_size)
-		add_memory(0, addr, block_size, MHP_NONE);
+		add_memory(0, addr, block_size,
+			   MACHINE_HAS_EDAT1 ?
+			   MHP_MEMMAP_ON_MEMORY | MHP_OFFLINE_INACCESSIBLE : MHP_NONE);
 skip_add:
 	first_rn = rn;
 	num = 1;
_

Patches currently in -mm which might be from sumanthk@linux.ibm.com are

mm-memory_hotplug-add-missing-mem_hotplug_lock.patch
mm-memory_hotplug-fix-error-handling-in-add_memory_resource.patch
mm-use-vmem_altmap-code-without-config_zone_device.patch
mm-memory_hotplug-introduce-mem_prepare_online-mem_finish_offline-notifiers.patch
s390-mm-allocate-vmemmap-pages-from-self-contained-memory-range.patch
s390-sclp-remove-unhandled-memory-notifier-type.patch
s390-mm-implement-mem_prepare_online-mem_finish_offline-notifiers.patch
s390-enable-mhp_memmap_on_memory.patch