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, 49 insertions, 0 deletions

diff --git a/Documentation/driver-api/auxiliary_bus.rst b/Documentation/driver-api/auxiliary_bus.rst
new file mode 100644
index 000000000..b236de773
--- /dev/null
+++ b/Documentation/driver-api/auxiliary_bus.rst
@@ -0,0 +1,49 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+.. _auxiliary_bus:
+
+=============
+Auxiliary Bus
+=============
+
+.. kernel-doc:: drivers/base/auxiliary.c
+   :doc: PURPOSE
+
+When Should the Auxiliary Bus Be Used
+=====================================
+
+.. kernel-doc:: drivers/base/auxiliary.c
+   :doc: USAGE
+
+
+Auxiliary Device Creation
+=========================
+
+.. kernel-doc:: include/linux/auxiliary_bus.h
+   :identifiers: auxiliary_device
+
+.. kernel-doc:: drivers/base/auxiliary.c
+   :identifiers: auxiliary_device_init __auxiliary_device_add
+
+Auxiliary Device Memory Model and Lifespan
+------------------------------------------
+
+.. kernel-doc:: include/linux/auxiliary_bus.h
+   :doc: DEVICE_LIFESPAN
+
+
+Auxiliary Drivers
+=================
+
+.. kernel-doc:: include/linux/auxiliary_bus.h
+   :identifiers: auxiliary_driver module_auxiliary_driver
+
+.. kernel-doc:: drivers/base/auxiliary.c
+   :identifiers: __auxiliary_driver_register auxiliary_driver_unregister
+
+Example Usage
+=============
+
+.. kernel-doc:: drivers/base/auxiliary.c
+   :doc: EXAMPLE
+