From: David Hildenbrand <david@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: David Hildenbrand <david@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Mike Rapoport <rppt@kernel.org>, Michal Hocko <mhocko@suse.com>,
Oscar Salvador <osalvador@suse.de>,
Jianyong Wu <Jianyong.Wu@arm.com>,
"Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
Vineet Gupta <vgupta@kernel.org>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Huacai Chen <chenhuacai@kernel.org>,
Jiaxun Yang <jiaxun.yang@flygoat.com>,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Eric Biederman <ebiederm@xmission.com>,
Arnd Bergmann <arnd@arndb.de>,
linux-snps-arc@lists.infradead.org, linux-ia64@vger.kernel.org,
linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org,
linux-s390@vger.kernel.org, linux-mm@kvack.org,
kexec@lists.infradead.org
Subject: [PATCH v2 2/5] memblock: improve MEMBLOCK_HOTPLUG documentation
Date: Mon, 4 Oct 2021 11:36:02 +0200 [thread overview]
Message-ID: <20211004093605.5830-3-david@redhat.com> (raw)
In-Reply-To: <20211004093605.5830-1-david@redhat.com>
The description of MEMBLOCK_HOTPLUG is currently short and consequently
misleading: we're actually dealing with a memory region that might get
hotunplugged later (i.e., the platform+firmware supports it), yet it is
indicated in the firmware-provided memory map as system ram that will just
get used by the system for any purpose when not taking special care. The
firmware marked this memory region as a hot(un)plugged (e.g., hotplugged
before reboot), implying that it might get hotunplugged again later.
Whether we consider this information depends on the "movable_node" kernel
commandline parameter: only with "movable_node" set, we'll try keeping
this memory hotunpluggable, for example, by not serving early allocations
from this memory region and by letting the buddy manage it using the
ZONE_MOVABLE.
Let's make this clearer by extending the documentation.
Note: kexec *has to* indicate this memory to the second kernel. With
"movable_node" set, we don't want to place kexec-images on this memory.
Without "movable_node" set, we don't care and can place kexec-images on
this memory. In both cases, after successful memory hotunplug, kexec has to
be re-armed to update the memory map for the second kernel and to place the
kexec-images somewhere else.
Signed-off-by: David Hildenbrand <david@redhat.com>
---
include/linux/memblock.h | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index 34de69b3b8ba..4ee8dd2d63a7 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -28,7 +28,11 @@ extern unsigned long long max_possible_pfn;
/**
* enum memblock_flags - definition of memory region attributes
* @MEMBLOCK_NONE: no special request
- * @MEMBLOCK_HOTPLUG: hotpluggable region
+ * @MEMBLOCK_HOTPLUG: memory region indicated in the firmware-provided memory
+ * map during early boot as hot(un)pluggable system RAM (e.g., memory range
+ * that might get hotunplugged later). With "movable_node" set on the kernel
+ * commandline, try keeping this memory region hotunpluggable. Does not apply
+ * to memblocks added ("hotplugged") after early boot.
* @MEMBLOCK_MIRROR: mirrored region
* @MEMBLOCK_NOMAP: don't add to kernel direct mapping and treat as
* reserved in the memory map; refer to memblock_mark_nomap() description
--
2.31.1
next prev parent reply other threads:[~2021-10-04 9:36 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-04 9:36 [PATCH v2 0/5] mm/memory_hotplug: full support for add_memory_driver_managed() with CONFIG_ARCH_KEEP_MEMBLOCK David Hildenbrand
2021-10-04 9:36 ` [PATCH v2 1/5] mm/memory_hotplug: handle memblock_add_node() failures in add_memory_resource() David Hildenbrand
2021-10-04 9:36 ` David Hildenbrand [this message]
2021-10-06 0:35 ` [PATCH v2 2/5] memblock: improve MEMBLOCK_HOTPLUG documentation Mike Rapoport
2021-10-04 9:36 ` [PATCH v2 3/5] memblock: allow to specify flags with memblock_add_node() David Hildenbrand
2021-10-04 19:31 ` Shahab Vahedi
2021-10-06 0:36 ` Mike Rapoport
2021-10-04 9:36 ` [PATCH v2 4/5] memblock: add MEMBLOCK_DRIVER_MANAGED to mimic IORESOURCE_SYSRAM_DRIVER_MANAGED David Hildenbrand
2021-10-06 0:35 ` Mike Rapoport
2021-10-04 9:36 ` [PATCH v2 5/5] mm/memory_hotplug: indicate MEMBLOCK_DRIVER_MANAGED with IORESOURCE_SYSRAM_DRIVER_MANAGED David Hildenbrand
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