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, 42 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-iio-trigger-sysfs b/Documentation/ABI/testing/sysfs-bus-iio-trigger-sysfs
new file mode 100644
index 000000000..04ac62305
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-iio-trigger-sysfs
@@ -0,0 +1,42 @@
+What:		/sys/bus/iio/devices/triggerX/trigger_now
+KernelVersion:	2.6.38
+Contact:	linux-iio@vger.kernel.org
+Description:
+		This file is provided by the iio-trig-sysfs stand-alone trigger
+		driver. Writing this file with any value triggers an event
+		driven driver, associated with this trigger, to capture data
+		into an in kernel buffer. This approach can be valuable during
+		automated testing or in situations, where other trigger methods
+		are not applicable. For example no RTC or spare GPIOs.
+		X is the IIO index of the trigger.
+
+What:		/sys/bus/iio/devices/triggerX/name
+KernelVersion:	2.6.39
+Contact:	linux-iio@vger.kernel.org
+Description:
+		The name attribute holds a description string for the current
+		trigger. In order to associate the trigger with an IIO device
+		one should write this name string to
+		/sys/bus/iio/devices/iio:deviceY/trigger/current_trigger.
+
+What:		/sys/bus/iio/devices/iio_sysfs_trigger/add_trigger
+KernelVersion:	2.6.39
+Contact:	linux-iio@vger.kernel.org
+Description:
+		This attribute is provided by the iio-trig-sysfs stand-alone
+		driver and it is used to activate the creation of a new trigger.
+		In order to achieve this, one should write a positive integer
+		into the associated file, which will serve as the id of the
+		trigger. If the trigger with the specified id is already present
+		in the system, an invalid argument message will be returned.
+
+What:		/sys/bus/iio/devices/iio_sysfs_trigger/remove_trigger
+KernelVersion:	2.6.39
+Contact:	linux-iio@vger.kernel.org
+Description:
+		This attribute is used to unregister and delete a previously
+		created trigger from the list of available triggers. In order to
+		achieve this, one should write a positive integer into the
+		associated file, representing the id of the trigger that needs
+		to be removed. If the trigger can't be found, an invalid
+		argument message will be returned to the user.