Add support for the newly added kernel memory auto onlining policy to Xen
ballon driver.
Suggested-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
Changes since v4:
- 'dom0' -> 'control domain', 'domU' -> 'target domain' in Kconfig
[David Vrabel]
- always call add_memory_resource() with memhp_auto_online [David Vrabel]
---
drivers/xen/Kconfig | 20 +++++++++++++-------
drivers/xen/balloon.c | 11 ++++++++++-
2 files changed, 23 insertions(+), 8 deletions(-)
diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index 73708ac..addcb7f 100644
--- a/drivers/xen/Kconfig
+++ b/drivers/xen/Kconfig
@@ -37,23 +37,29 @@ 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,
- 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'"
config XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
int "Hotplugged memory limit (in GiB) for a PV guest"
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 890c3b5..f8cca0c 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -338,7 +338,16 @@ static enum bp_state reserve_additional_memory(void)
}
#endif
- 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.
+ */
+ mutex_unlock(&balloon_mutex);
+ rc = add_memory_resource(nid, resource, memhp_auto_online);
+ mutex_lock(&balloon_mutex);
+
if (rc) {
pr_warn("Cannot add additional memory (%i)\n", rc);
goto err;
--
2.5.0
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