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, 299 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-most b/Documentation/ABI/testing/sysfs-bus-most
new file mode 100644
index 000000000..38cc03e40
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-most
@@ -0,0 +1,299 @@
+What:		/sys/bus/most/devices/<dev>/description
+Date:		March 2017
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		Provides information about the physical location of the
+		device. Hardware attached via USB, for instance,
+		might return <1-1.1:1.0>
+Users:
+
+What:		/sys/bus/most/devices/<dev>/interface
+Date:		March 2017
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		Indicates the type of peripheral interface the device uses.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/dci
+Date:		June 2016
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		If the network interface controller is attached via USB, a dci
+		directory is created that allows applications to read and
+		write the controller's DCI registers.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/dci/arb_address
+Date:		June 2016
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		This is used to set an arbitrary DCI register address an
+		application wants to read from or write to.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/dci/arb_value
+Date:		June 2016
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		This is used to read and write the DCI register whose address
+		is stored in arb_address.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/dci/mep_eui48_hi
+Date:		June 2016
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		This is used to check and configure the MAC address.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/dci/mep_eui48_lo
+Date:		June 2016
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		This is used to check and configure the MAC address.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/dci/mep_eui48_mi
+Date:		June 2016
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		This is used to check and configure the MAC address.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/dci/mep_filter
+Date:		June 2016
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		This is used to check and configure the MEP filter address.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/dci/mep_hash0
+Date:		June 2016
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		This is used to check and configure the MEP hash table.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/dci/mep_hash1
+Date:		June 2016
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		This is used to check and configure the MEP hash table.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/dci/mep_hash2
+Date:		June 2016
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		This is used to check and configure the MEP hash table.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/dci/mep_hash3
+Date:		June 2016
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		This is used to check and configure the MEP hash table.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/dci/ni_state
+Date:		June 2016
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		Indicates the current network interface state.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/dci/node_address
+Date:		June 2016
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		Indicates the current node address.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/dci/node_position
+Date:		June 2016
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		Indicates the current node position.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/dci/packet_bandwidth
+Date:		June 2016
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		Indicates the configured packet bandwidth.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/dci/sync_ep
+Date:		June 2016
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		Triggers the controller's synchronization process for a certain
+		endpoint.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/<channel>/
+Date:		March 2017
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		For every channel of the device a directory is created, whose
+		name is dictated by the HDM. This enables an application to
+		collect information about the channel's capabilities and
+		configure it.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/<channel>/available_datatypes
+Date:		March 2017
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		Indicates the data types the channel can transport.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/<channel>/available_directions
+Date:		March 2017
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		Indicates the directions the channel is capable of.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/<channel>/number_of_packet_buffers
+Date:		March 2017
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		Indicates the number of packet buffers the channel can
+		handle.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/<channel>/number_of_stream_buffers
+Date:		March 2017
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		Indicates the number of streaming buffers the channel can
+		handle.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/<channel>/size_of_packet_buffer
+Date:		March 2017
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		Indicates the size of a packet buffer the channel can
+		handle.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/<channel>/size_of_stream_buffer
+Date:		March 2017
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		Indicates the size of a streaming buffer the channel can
+		handle.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/<channel>/set_number_of_buffers
+Date:		March 2017
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		This is to read back the configured number of buffers of
+		the channel.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/<channel>/set_buffer_size
+Date:		March 2017
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		This is to read back the configured buffer size of the channel.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/<channel>/set_direction
+Date:		March 2017
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		This is to read back the configured direction of the channel.
+		The following strings will be accepted::
+
+			'tx',
+			'rx'
+Users:
+
+What:		/sys/bus/most/devices/<dev>/<channel>/set_datatype
+Date:		March 2017
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		This is to read back the configured data type of the channel.
+		The following strings will be accepted::
+
+			'control',
+			'async',
+			'sync',
+			'isoc_avp'
+Users:
+
+What:		/sys/bus/most/devices/<dev>/<channel>/set_subbuffer_size
+Date:		March 2017
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		This is to read back the configured subbuffer size of
+		the channel.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/<channel>/set_packets_per_xact
+Date:		March 2017
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		This is to read back the configured number of packets per
+		transaction of the channel. This is only applicable when
+		connected via USB.
+Users:
+
+What:		/sys/bus/most/devices/<dev>/<channel>/channel_starving
+Date:		March 2017
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		Indicates whether channel ran out of buffers.
+Users:
+
+What:		/sys/bus/most/drivers/most_core/components
+Date:		March 2017
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		This is used to retrieve a list of registered components.
+Users:
+
+What:		/sys/bus/most/drivers/most_core/links
+Date:		March 2017
+KernelVersion:	4.15
+Contact:	Christian Gromm <christian.gromm@microchip.com>
+Description:
+		This is used to retrieve a list of established links.
+Users: