From 119e9db233ad0f4cbd4cfb9f9385a7bca378b37d Mon Sep 17 00:00:00 2001 From: Zeng Chi Date: Mon, 21 Sep 2026 18:24:42 +0800 Subject: KVM: Don't pre-reserve xarray entries when storing empty/NULL attributes Skip the xarray reservation loop when clearing all memory attributes, as storing NULL only erases the entry and never needs to allocate, so no reservation (and no cleanup of a failed one) is required in that case. Suggested-by: Sean Christopherson Cc: David Ballesteros Signed-off-by: Zeng Chi Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com [sean: split to separate patch] Signed-off-by: Sean Christopherson --- Documentation/admin-guide/sysctl/xen.rst | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) create mode 100644 Documentation/admin-guide/sysctl/xen.rst (limited to 'Documentation/admin-guide/sysctl/xen.rst') diff --git a/Documentation/admin-guide/sysctl/xen.rst b/Documentation/admin-guide/sysctl/xen.rst new file mode 100644 index 000000000..6c5edc3e5 --- /dev/null +++ b/Documentation/admin-guide/sysctl/xen.rst @@ -0,0 +1,31 @@ +=============== +/proc/sys/xen/ +=============== + +Copyright (c) 2026, Shubham Chakraborty + +For general info and legal blurb, please look in +Documentation/admin-guide/sysctl/index.rst. + +------------------------------------------------------------------------------ + +These files show up in ``/proc/sys/xen/``, depending on the +kernel configuration: + +.. contents:: :local: + +balloon/hotplug_unpopulated +=========================== + +This flag controls whether unpopulated memory ranges are automatically +hotplugged as system RAM. + +- ``0``: Unpopulated ranges are not hotplugged (default). +- ``1``: Unpopulated ranges are automatically hotplugged. + +When enabled, the Xen balloon driver will add memory regions that are +marked as unpopulated in the Xen memory map to the system as usable RAM. +This allows for dynamic memory expansion in Xen guest domains. + +This option is only available when the kernel is built with +``CONFIG_XEN_BALLOON_MEMORY_HOTPLUG`` enabled. -- cgit v1.3.1