KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

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 <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-devices b/Documentation/ABI/testing/sysfs-devices
new file mode 100644
index 000000000..5fcc94358
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-devices
@@ -0,0 +1,25 @@
+What:		/sys/devices
+Date:		February 2006
+Contact:	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+Description:
+		The /sys/devices tree contains a snapshot of the
+		internal state of the kernel device tree.  Devices will
+		be added and removed dynamically as the machine runs,
+		and between different kernel versions, the layout of the
+		devices within this tree will change.
+
+		Please do not rely on the format of this tree because of
+		this.  If a program wishes to find different things in
+		the tree, please use the /sys/class structure and rely
+		on the symlinks there to point to the proper location
+		within the /sys/devices tree of the individual devices.
+		Or rely on the uevent messages to notify programs of
+		devices being added and removed from this tree to find
+		the location of those devices.
+
+		Note that sometimes not all devices along the directory
+		chain will have emitted uevent messages, so userspace
+		programs must be able to handle such occurrences.
+
+Users:
+	udev <linux-hotplug-devel@lists.sourceforge.net>