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, 29 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-mcb b/Documentation/ABI/testing/sysfs-bus-mcb
new file mode 100644
index 000000000..77947c509
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-mcb
@@ -0,0 +1,29 @@
+What:		/sys/bus/mcb/devices/mcb:X
+Date:		March 2016
+KernelVersion:	4.7
+Contact:	Johannes Thumshirn <jth@kernel.org>
+Description:	Hardware chip or device hosting the MEN chameleon bus
+
+What:		/sys/bus/mcb/devices/mcb:X/revision
+Date:		March 2016
+KernelVersion:	4.7
+Contact:	Johannes Thumshirn <jth@kernel.org>
+Description:	The FPGA's revision number
+
+What:		/sys/bus/mcb/devices/mcb:X/minor
+Date:		March 2016
+KernelVersion:	4.7
+Contact:	Johannes Thumshirn <jth@kernel.org>
+Description:	The FPGA's minor number
+
+What:		/sys/bus/mcb/devices/mcb:X/model
+Date:		March 2016
+KernelVersion:	4.7
+Contact:	Johannes Thumshirn <jth@kernel.org>
+Description:	The FPGA's model number
+
+What:		/sys/bus/mcb/devices/mcb:X/name
+Date:		March 2016
+KernelVersion:	4.7
+Contact:	Johannes Thumshirn <jth@kernel.org>
+Description:	The FPGA's name