Commit 703fc13a authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Linus Torvalds

xen_balloon: support memory auto onlining policy

Add support for the newly added kernel memory auto onlining policy to
Xen ballon driver.
Signed-off-by: default avatarVitaly Kuznetsov <>
Suggested-by: default avatarDaniel Kiper <>
Reviewed-by: default avatarDaniel Kiper <>
Acked-by: default avatarDavid Vrabel <>
Cc: Jonathan Corbet <>
Cc: Greg Kroah-Hartman <>
Cc: Daniel Kiper <>
Cc: Dan Williams <>
Cc: Tang Chen <>
Cc: David Rientjes <>
Cc: Naoya Horiguchi <>
Cc: Xishi Qiu <>
Cc: Mel Gorman <>
Cc: "K. Y. Srinivasan" <>
Cc: Igor Mammedov <>
Cc: Kay Sievers <>
Cc: Konrad Rzeszutek Wilk <>
Cc: Boris Ostrovsky <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 31bc3858
......@@ -37,23 +37,30 @@ config XEN_BALLOON_MEMORY_HOTPLUG
Memory could be hotplugged in following steps:
1) dom0: xl mem-max <domU> <maxmem>
1) target domain: ensure that memory auto online policy is in
effect by checking /sys/devices/system/memory/auto_online_blocks
file (should be 'online').
2) control domain: xl mem-max <target-domain> <maxmem>
where <maxmem> is >= requested memory size,
2) dom0: xl mem-set <domU> <memory>
3) control domain: xl mem-set <target-domain> <memory>
where <memory> is requested memory size; alternatively memory
could be added by writing proper value to
/sys/devices/system/xen_memory/xen_memory0/target or
/sys/devices/system/xen_memory/xen_memory0/target_kb on dumU,
/sys/devices/system/xen_memory/xen_memory0/target_kb on the
target domain.
3) domU: for i in /sys/devices/system/memory/memory*/state; do \
[ "`cat "$i"`" = offline ] && echo online > "$i"; done
Alternatively, if memory auto onlining was not requested at step 1
the newly added memory can be manually onlined in the target domain
by doing the following:
Memory could be onlined automatically on domU by adding following line to udev rules:
for i in /sys/devices/system/memory/memory*/state; do \
[ "`cat "$i"`" = offline ] && echo online > "$i"; done
SUBSYSTEM=="memory", ACTION=="add", RUN+="/bin/sh -c '[ -f /sys$devpath/state ] && echo online > /sys$devpath/state'"
or by adding the following line to udev rules:
In that case step 3 should be omitted.
SUBSYSTEM=="memory", ACTION=="add", RUN+="/bin/sh -c '[ -f /sys$devpath/state ] && echo online > /sys$devpath/state'"
int "Hotplugged memory limit (in GiB) for a PV guest"
......@@ -338,7 +338,16 @@ static enum bp_state reserve_additional_memory(void)
rc = add_memory_resource(nid, resource, false);
* add_memory_resource() will call online_pages() which in its turn
* will call xen_online_page() callback causing deadlock if we don't
* release balloon_mutex here. Unlocking here is safe because the
* callers drop the mutex before trying again.
rc = add_memory_resource(nid, resource, memhp_auto_online);
if (rc) {
pr_warn("Cannot add additional memory (%i)\n", rc);
goto err;
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