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, 57 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-driver-uacce b/Documentation/ABI/testing/sysfs-driver-uacce
new file mode 100644
index 000000000..d3f0b8f3c
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-uacce
@@ -0,0 +1,57 @@
+What:           /sys/class/uacce/<dev_name>/api
+Date:           Feb 2020
+KernelVersion:  5.7
+Contact:        linux-accelerators@lists.ozlabs.org
+Description:    Api of the device
+                Can be any string and up to userspace to parse.
+                Application use the api to match the correct driver
+
+What:           /sys/class/uacce/<dev_name>/flags
+Date:           Feb 2020
+KernelVersion:  5.7
+Contact:        linux-accelerators@lists.ozlabs.org
+Description:    Attributes of the device, see UACCE_DEV_xxx flag defined in uacce.h
+
+What:           /sys/class/uacce/<dev_name>/available_instances
+Date:           Feb 2020
+KernelVersion:  5.7
+Contact:        linux-accelerators@lists.ozlabs.org
+Description:    Available instances left of the device
+                Return -ENODEV if uacce_ops get_available_instances is not provided
+
+What:           /sys/class/uacce/<dev_name>/isolate_strategy
+Date:           Nov 2022
+KernelVersion:  6.1
+Contact:        linux-accelerators@lists.ozlabs.org
+Description:    (RW) A sysfs node that configure the error threshold for the hardware
+                isolation strategy. This size is a configured integer value, which is the
+                number of threshold for hardware errors occurred in one hour. The default is 0.
+                0 means never isolate the device. The maximum value is 65535. You can write
+                a number of threshold based on your hardware.
+
+What:           /sys/class/uacce/<dev_name>/isolate
+Date:           Nov 2022
+KernelVersion:  6.1
+Contact:        linux-accelerators@lists.ozlabs.org
+Description:    (R) A sysfs node that read the device isolated state. The value 1
+                means the device is unavailable. The 0 means the device is
+                available.
+
+What:           /sys/class/uacce/<dev_name>/algorithms
+Date:           Feb 2020
+KernelVersion:  5.7
+Contact:        linux-accelerators@lists.ozlabs.org
+Description:    Algorithms supported by this accelerator, separated by new line.
+                Can be any string and up to userspace to parse.
+
+What:           /sys/class/uacce/<dev_name>/region_mmio_size
+Date:           Feb 2020
+KernelVersion:  5.7
+Contact:        linux-accelerators@lists.ozlabs.org
+Description:    Size (bytes) of mmio region queue file
+
+What:           /sys/class/uacce/<dev_name>/region_dus_size
+Date:           Feb 2020
+KernelVersion:  5.7
+Contact:        linux-accelerators@lists.ozlabs.org
+Description:    Size (bytes) of dus region queue file