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, 105 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-driver-wacom b/Documentation/ABI/testing/sysfs-driver-wacom
new file mode 100644
index 000000000..16acaa571
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-wacom
@@ -0,0 +1,105 @@
+What:		/sys/bus/hid/devices/<bus>:<vid>:<pid>.<n>/speed
+Date:		April 2010
+KernelVersion:	2.6.35
+Contact:	linux-bluetooth@vger.kernel.org
+Description:
+		The /sys/bus/hid/devices/<bus>:<vid>:<pid>.<n>/speed file
+		controls reporting speed of Wacom bluetooth tablet. Reading
+		from this file returns 1 if tablet reports in high speed mode
+		or 0 otherwise. Writing to this file one of these values
+		switches reporting speed.
+
+What:		/sys/bus/hid/devices/<bus>:<vid>:<pid>.<n>/wacom_led/led
+Date:		August 2014
+Contact:	linux-input@vger.kernel.org
+Description:
+		Attribute group for control of the status LEDs and the OLEDs.
+		This attribute group is only available for Intuos 4 M, L,
+		and XL (with LEDs and OLEDs), Intuos 4 WL, Intuos 5 (LEDs only),
+		Intuos Pro (LEDs only) and Cintiq 21UX2 and Cintiq 24HD
+		(LEDs only). Therefore its presence implicitly signifies the
+		presence of said LEDs and OLEDs on the tablet device.
+
+What:		/sys/bus/hid/devices/<bus>:<vid>:<pid>.<n>/wacom_led/status0_luminance
+Date:		August 2014
+Contact:	linux-input@vger.kernel.org
+Description:
+		<obsoleted by the LED class API now exported by the driver>
+		Writing to this file sets the status LED luminance (1..127)
+		when the stylus does not touch the tablet surface, and no
+		button is pressed on the stylus. This luminance level is
+		normally lower than the level when a button is pressed.
+
+What:		/sys/bus/hid/devices/<bus>:<vid>:<pid>.<n>/wacom_led/status1_luminance
+Date:		August 2014
+Contact:	linux-input@vger.kernel.org
+Description:
+		<obsoleted by the LED class API now exported by the driver>
+		Writing to this file sets the status LED luminance (1..127)
+		when the stylus touches the tablet surface, or any button is
+		pressed on the stylus.
+
+What:		/sys/bus/hid/devices/<bus>:<vid>:<pid>.<n>/wacom_led/status_led0_select
+Date:		August 2014
+Contact:	linux-input@vger.kernel.org
+Description:
+		<obsoleted by the LED class API now exported by the driver>
+		Writing to this file sets which one of the four (for Intuos 4
+		and Intuos 5) or of the right four (for Cintiq 21UX2 and Cintiq
+		24HD) status LEDs is active (0..3). The other three LEDs on the
+		same side are always inactive.
+
+What:		/sys/bus/hid/devices/<bus>:<vid>:<pid>.<n>/wacom_led/status_led1_select
+Date:		August 2014
+Contact:	linux-input@vger.kernel.org
+Description:
+		<obsoleted by the LED class API now exported by the driver>
+		Writing to this file sets which one of the left four (for Cintiq 21UX2
+		and Cintiq 24HD) status LEDs is active (0..3). The other three LEDs on
+		the left are always inactive.
+
+What:		/sys/bus/hid/devices/<bus>:<vid>:<pid>.<n>/wacom_led/buttons_luminance
+Date:		August 2014
+Contact:	linux-input@vger.kernel.org
+Description:
+		Writing to this file sets the overall luminance level (0..15)
+		of all eight button OLED displays.
+
+What:		/sys/bus/hid/devices/<bus>:<vid>:<pid>.<n>/wacom_led/button<n>_rawimg
+Date:		August 2014
+Contact:	linux-input@vger.kernel.org
+Description:
+		When writing a 1024 byte raw image in Wacom Intuos 4
+		interleaving format to the file, the image shows up on Button N
+		of the device. The image is a 64x32 pixel 4-bit gray image. The
+		1024 byte binary is split up into 16x 64 byte chunks. Each 64
+		byte chunk encodes the image data for two consecutive lines on
+		the display. The low nibble of each byte contains the first
+		line, and the high nibble contains the second line.
+		When the Wacom Intuos 4 is connected over Bluetooth, the
+		image has to contain 256 bytes (64x32 px 1 bit colour).
+		The format is also scrambled, like in the USB mode, and it can
+		be summarized by converting::
+
+					    76543210 into GECA6420.
+					    HGFEDCBA      HFDB7531
+
+What:		/sys/bus/hid/devices/<bus>:<vid>:<pid>.<n>/wacom_remote/unpair_remote
+Date:		July 2015
+Contact:	linux-input@vger.kernel.org
+Description:
+		Writing the character sequence '*' followed by a newline to
+		this file will delete all of the current pairings on the
+		device. Other character sequences are reserved. This file is
+		write only.
+
+What:		/sys/bus/hid/devices/<bus>:<vid>:<pid>.<n>/wacom_remote/<serial_number>/remote_mode
+Date:		July 2015
+Contact:	linux-input@vger.kernel.org
+Description:
+		<obsoleted by the LED class API now exported by the driver>
+		Reading from this file reports the mode status of the
+		remote as indicated by the LED lights on the device. If no
+		reports have been received from the paired device, reading
+		from this file will report '-1'. The mode is read-only
+		and cannot be set through the driver.