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, 96 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-switchtec b/Documentation/ABI/testing/sysfs-class-switchtec
new file mode 100644
index 000000000..76c7a661a
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-switchtec
@@ -0,0 +1,96 @@
+switchtec - Microsemi Switchtec PCI Switch Management Endpoint
+
+For details on this subsystem look at Documentation/driver-api/switchtec.rst.
+
+What: 		/sys/class/switchtec
+Date:		05-Jan-2017
+KernelVersion:	v4.11
+Contact:	Logan Gunthorpe <logang@deltatee.com>
+Description:	The switchtec class subsystem folder.
+		Each registered switchtec driver is represented by a switchtecX
+		subfolder (X being an integer >= 0).
+
+
+What:		/sys/class/switchtec/switchtec[0-9]+/component_id
+Date:		05-Jan-2017
+KernelVersion:	v4.11
+Contact:	Logan Gunthorpe <logang@deltatee.com>
+Description:	Component identifier as stored in the hardware (eg. PM8543)
+		(read only)
+Values: 	arbitrary string.
+
+
+What:		/sys/class/switchtec/switchtec[0-9]+/component_revision
+Date:		05-Jan-2017
+KernelVersion:	v4.11
+Contact:	Logan Gunthorpe <logang@deltatee.com>
+Description:	Component revision stored in the hardware (read only)
+Values: 	integer.
+
+
+What:		/sys/class/switchtec/switchtec[0-9]+/component_vendor
+Date:		05-Jan-2017
+KernelVersion:	v4.11
+Contact:	Logan Gunthorpe <logang@deltatee.com>
+Description:	Component vendor as stored in the hardware (eg. MICROSEM)
+		(read only)
+Values: 	arbitrary string.
+
+
+What:		/sys/class/switchtec/switchtec[0-9]+/device_version
+Date:		05-Jan-2017
+KernelVersion:	v4.11
+Contact:	Logan Gunthorpe <logang@deltatee.com>
+Description:	Device version as stored in the hardware (read only)
+Values: 	integer.
+
+
+What:		/sys/class/switchtec/switchtec[0-9]+/fw_version
+Date:		05-Jan-2017
+KernelVersion:	v4.11
+Contact:	Logan Gunthorpe <logang@deltatee.com>
+Description:	Currently running firmware version (read only)
+Values: 	integer (in hexadecimal).
+
+
+What:		/sys/class/switchtec/switchtec[0-9]+/partition
+Date:		05-Jan-2017
+KernelVersion:	v4.11
+Contact:	Logan Gunthorpe <logang@deltatee.com>
+Description:	Partition number for this device in the switch (read only)
+Values: 	integer.
+
+
+What:		/sys/class/switchtec/switchtec[0-9]+/partition_count
+Date:		05-Jan-2017
+KernelVersion:	v4.11
+Contact:	Logan Gunthorpe <logang@deltatee.com>
+Description:	Total number of partitions in the switch (read only)
+Values: 	integer.
+
+
+What:		/sys/class/switchtec/switchtec[0-9]+/product_id
+Date:		05-Jan-2017
+KernelVersion:	v4.11
+Contact:	Logan Gunthorpe <logang@deltatee.com>
+Description:	Product identifier as stored in the hardware (eg. PSX 48XG3)
+		(read only)
+Values: 	arbitrary string.
+
+
+What:		/sys/class/switchtec/switchtec[0-9]+/product_revision
+Date:		05-Jan-2017
+KernelVersion:	v4.11
+Contact:	Logan Gunthorpe <logang@deltatee.com>
+Description:	Product revision stored in the hardware (eg. RevB)
+		(read only)
+Values: 	arbitrary string.
+
+
+What:		/sys/class/switchtec/switchtec[0-9]+/product_vendor
+Date:		05-Jan-2017
+KernelVersion:	v4.11
+Contact:	Logan Gunthorpe <logang@deltatee.com>
+Description:	Product vendor as stored in the hardware (eg. MICROSEM)
+		(read only)
+Values: 	arbitrary string.