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, 56 insertions, 0 deletions

diff --git a/Documentation/driver-api/pldmfw/driver-ops.rst b/Documentation/driver-api/pldmfw/driver-ops.rst
new file mode 100644
index 000000000..f0654783d
--- /dev/null
+++ b/Documentation/driver-api/pldmfw/driver-ops.rst
@@ -0,0 +1,56 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+=========================
+Driver-specific callbacks
+=========================
+
+The ``pldmfw`` module relies on the device driver for implementing device
+specific behavior using the following operations.
+
+``.match_record``
+-----------------
+
+The ``.match_record`` operation is used to determine whether a given PLDM
+record matches the device being updated. This requires comparing the record
+descriptors in the record with information from the device. Many record
+descriptors are defined by the PLDM standard, but it is also allowed for
+devices to implement their own descriptors.
+
+The ``.match_record`` operation should return true if a given record matches
+the device.
+
+``.send_package_data``
+----------------------
+
+The ``.send_package_data`` operation is used to send the device-specific
+package data in a record to the device firmware. If the matching record
+provides package data, ``pldmfw`` will call the ``.send_package_data``
+function with a pointer to the package data and with the package data
+length. The device driver should send this data to firmware.
+
+``.send_component_table``
+-------------------------
+
+The ``.send_component_table`` operation is used to forward component
+information to the device. It is called once for each applicable component,
+that is, for each component indicated by the matching record. The
+device driver should send the component information to the device firmware,
+and wait for a response. The provided transfer flag indicates whether this
+is the first, last, or a middle component, and is expected to be forwarded
+to firmware as part of the component table information. The driver should an
+error in the case when the firmware indicates that the component cannot be
+updated, or return zero if the component can be updated.
+
+``.flash_component``
+--------------------
+
+The ``.flash_component`` operation is used to inform the device driver to
+flash a given component. The driver must perform any steps necessary to send
+the component data to the device.
+
+``.finalize_update``
+--------------------
+
+The ``.finalize_update`` operation is used by the ``pldmfw`` library in
+order to allow the device driver to perform any remaining device specific
+logic needed to finish the update.