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| author | Baoquan He <bhe@redhat.com> | 2020-04-07 05:06:50 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-04-07 19:43:40 +0200 |
| commit | f3cd4c865b8ad61ff6dc61feba759a98ca06f039 (patch) | |
| tree | e8f7199d2b193383e8cfda63ea45e636ad52285c /mm/memory_hotplug.c | |
| parent | mm/page_ext.c: drop pfn_present() check when onlining (diff) | |
| download | linux-f3cd4c865b8ad61ff6dc61feba759a98ca06f039.tar.xz linux-f3cd4c865b8ad61ff6dc61feba759a98ca06f039.zip | |
mm/memory_hotplug.c: only respect mem= parameter during boot stage
In commit 357b4da50a62 ("x86: respect memory size limiting via mem=
parameter") a global varialbe max_mem_size is added to store the value
parsed from 'mem= ', then checked when memory region is added. This truly
stops those DIMMs from being added into system memory during boot-time.
However, it also limits the later memory hotplug functionality. Any DIMM
can't be hotplugged any more if its region is beyond the max_mem_size. We
will get errors like:
[ 216.387164] acpi PNP0C80:02: add_memory failed
[ 216.389301] acpi PNP0C80:02: acpi_memory_enable_device() error
[ 216.392187] acpi PNP0C80:02: Enumeration failure
This will cause issue in a known use case where 'mem=' is added to the
hypervisor. The memory that lies after 'mem=' boundary will be assigned
to KVM guests. After commit 357b4da50a62 merged, memory can't be extended
dynamically if system memory on hypervisor is not sufficient.
So fix it by also checking if it's during boot-time restricting to add
memory. Otherwise, skip the restriction.
And also add this use case to document of 'mem=' kernel parameter.
Fixes: 357b4da50a62 ("x86: respect memory size limiting via mem= parameter")
Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Juergen Gross <jgross@suse.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Link: http://lkml.kernel.org/r/20200204050643.20925-1-bhe@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memory_hotplug.c')
| -rw-r--r-- | mm/memory_hotplug.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 005eab3411e5..d6f813cc12c1 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -105,7 +105,13 @@ static struct resource *register_memory_resource(u64 start, u64 size) unsigned long flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY; char *resource_name = "System RAM"; - if (start + size > max_mem_size) + /* + * Make sure value parsed from 'mem=' only restricts memory adding + * while booting, so that memory hotplug won't be impacted. Please + * refer to document of 'mem=' in kernel-parameters.txt for more + * details. + */ + if (start + size > max_mem_size && system_state < SYSTEM_RUNNING) return ERR_PTR(-E2BIG); /* |