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-class-mei b/Documentation/ABI/testing/sysfs-class-mei
new file mode 100644
index 000000000..1db36ddf8
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-mei
@@ -0,0 +1,105 @@
+What:		/sys/class/mei/
+Date:		May 2014
+KernelVersion:	3.17
+Contact:	Tomas Winkler <tomas.winkler@intel.com>
+Description:
+		The mei/ class sub-directory belongs to mei device class
+
+
+What:		/sys/class/mei/mei<N>/
+Date:		May 2014
+KernelVersion:	3.17
+Contact:	Tomas Winkler <tomas.winkler@intel.com>
+Description:
+		The /sys/class/mei/meiN directory is created for
+		each probed mei device
+
+What:		/sys/class/mei/mei<N>/fw_status
+Date:		Nov 2014
+KernelVersion:	3.19
+Contact:	Tomas Winkler <tomas.winkler@intel.com>
+Description:	Display fw status registers content
+
+		The ME FW writes its status information into fw status
+		registers for BIOS and OS to monitor fw health.
+
+		The register contains running state, power management
+		state, error codes, and others. The way the registers
+		are decoded depends on PCH or SoC generation.
+		Also number of registers varies between 1 and 6
+		depending on generation.
+
+What:		/sys/class/mei/mei<N>/hbm_ver
+Date:		Aug 2016
+KernelVersion:	4.9
+Contact:	Tomas Winkler <tomas.winkler@intel.com>
+Description:	Display the negotiated HBM protocol version.
+
+		The HBM protocol version negotiated
+		between the driver and the device.
+
+What:		/sys/class/mei/mei<N>/hbm_ver_drv
+Date:		Aug 2016
+KernelVersion:	4.9
+Contact:	Tomas Winkler <tomas.winkler@intel.com>
+Description:	Display the driver HBM protocol version.
+
+		The HBM protocol version supported by the driver.
+
+What:		/sys/class/mei/mei<N>/tx_queue_limit
+Date:		Jan 2018
+KernelVersion:	4.16
+Contact:	Tomas Winkler <tomas.winkler@intel.com>
+Description:	Configure tx queue limit
+
+		Set maximal number of pending writes
+		per opened session.
+
+What:		/sys/class/mei/mei<N>/fw_ver
+Date:		May 2018
+KernelVersion:	4.18
+Contact:	Tomas Winkler <tomas.winkler@intel.com>
+Description:	Display the ME firmware version.
+
+		The version of the platform ME firmware is in format:
+		<platform>:<major>.<minor>.<milestone>.<build_no>.
+		There can be up to three such blocks for different
+		FW components.
+
+What:		/sys/class/mei/mei<N>/dev_state
+Date:		Mar 2019
+KernelVersion:	5.1
+Contact:	Tomas Winkler <tomas.winkler@intel.com>
+Description:	Display the ME device state.
+
+		The device state can have following values:
+		INITIALIZING
+		INIT_CLIENTS
+		ENABLED
+		RESETTING
+		DISABLED
+		POWER_DOWN
+		POWER_UP
+
+What:		/sys/class/mei/mei<N>/trc
+Date:		Nov 2019
+KernelVersion:	5.5
+Contact:	Tomas Winkler <tomas.winkler@intel.com>
+Description:	Display trc status register content
+
+		The ME FW writes Glitch Detection HW (TRC)
+		status information into trc status register
+		for BIOS and OS to monitor fw health.
+
+What:		/sys/class/mei/mei<N>/kind
+Date:		Jul 2020
+KernelVersion:	5.8
+Contact:	Tomas Winkler <tomas.winkler@intel.com>
+Description:	Display kind of the device
+
+		Generic devices are marked as "mei"
+		while special purpose have their own
+		names.
+		Available options:
+		- mei:  generic mei device.
+		- itouch:  itouch (ipts) mei device.