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, 167 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-driver-qat b/Documentation/ABI/testing/sysfs-driver-qat
new file mode 100644
index 000000000..b0561b9fc
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-qat
@@ -0,0 +1,167 @@
+What:		/sys/bus/pci/devices/<BDF>/qat/state
+Date:		June 2022
+KernelVersion:	6.0
+Contact:	qat-linux@intel.com
+Description:	(RW) Reports the current state of the QAT device. Write to
+		the file to start or stop the device.
+
+		The values are:
+
+		* up: the device is up and running
+		* down: the device is down
+
+
+		It is possible to transition the device from up to down only
+		if the device is up and vice versa.
+
+		This attribute is available for qat_4xxx and qat_6xxx devices.
+
+What:		/sys/bus/pci/devices/<BDF>/qat/cfg_services
+Date:		June 2022
+KernelVersion:	6.0
+Contact:	qat-linux@intel.com
+Description:	(RW) Reports the current configuration of the QAT device.
+		Write to the file to change the configured services.
+
+		One or more services can be enabled per device.
+		Certain configurations are restricted to specific device types;
+		where applicable this is explicitly indicated, for example
+		(qat_6xxx) denotes applicability exclusively to that device series.
+
+		The available services include:
+
+		* sym: Configures the device for symmetric cryptographic operations.
+		* asym: Configures the device for asymmetric cryptographic operations.
+		* dc: Configures the device for compression and decompression
+		  operations.
+		* dcc: Similar to dc, but with the additional dc chaining feature
+		  enabled, cipher then compress (qat_6xxx), hash then compression.
+		  If this is not required choose dc.
+		* decomp: Configures the device for decompression operations (qat_6xxx).
+
+		Service combinations are permitted for all services except dcc.
+		On QAT GEN4 devices (qat_4xxx driver) a maximum of two services can be
+		combined and on QAT GEN6 devices (qat_6xxx driver ) a maximum of three
+		services can be combined.
+		The order of services is not significant. For instance, sym;asym is
+		functionally equivalent to asym;sym.
+
+		It is possible to set the configuration only if the device
+		is in the `down` state (see /sys/bus/pci/devices/<BDF>/qat/state)
+
+		The following example shows how to change the configuration of
+		a device configured for running crypto services in order to
+		run data compression::
+
+			# cat /sys/bus/pci/devices/<BDF>/qat/state
+			up
+			# cat /sys/bus/pci/devices/<BDF>/qat/cfg_services
+			sym;asym
+			# echo down > /sys/bus/pci/devices/<BDF>/qat/state
+			# echo dc > /sys/bus/pci/devices/<BDF>/qat/cfg_services
+			# echo up > /sys/bus/pci/devices/<BDF>/qat/state
+			# cat /sys/bus/pci/devices/<BDF>/qat/cfg_services
+			dc
+
+		This attribute is available for qat_4xxx and qat_6xxx devices.
+
+What:		/sys/bus/pci/devices/<BDF>/qat/pm_idle_enabled
+Date:		June 2023
+KernelVersion:	6.5
+Contact:	qat-linux@intel.com
+Description:	(RW) This configuration option provides a way to force the device into remaining in
+		the MAX power state.
+		If idle support is enabled the device will transition to the `MIN` power state when
+		idle, otherwise will stay in the MAX power state.
+		Write to the file to enable or disable idle support.
+
+		The values are:
+
+		* 0: idle support is disabled
+		* 1: idle support is enabled
+
+		Default value is 1.
+
+		It is possible to set the pm_idle_enabled value only if the device
+		is in the `down` state (see /sys/bus/pci/devices/<BDF>/qat/state)
+
+		The following example shows how to change the pm_idle_enabled of
+		a device::
+
+			# cat /sys/bus/pci/devices/<BDF>/qat/state
+			up
+			# cat /sys/bus/pci/devices/<BDF>/qat/pm_idle_enabled
+			1
+			# echo down > /sys/bus/pci/devices/<BDF>/qat/state
+			# echo 0 > /sys/bus/pci/devices/<BDF>/qat/pm_idle_enabled
+			# echo up > /sys/bus/pci/devices/<BDF>/qat/state
+			# cat /sys/bus/pci/devices/<BDF>/qat/pm_idle_enabled
+			0
+
+		This attribute is available for qat_4xxx and qat_6xxx devices.
+
+What:		/sys/bus/pci/devices/<BDF>/qat/rp2srv
+Date:		January 2024
+KernelVersion:	6.7
+Contact:	qat-linux@intel.com
+Description:
+		(RW) This attribute provides a way for a user to query a
+		specific ring pair for the type of service that it is currently
+		configured for.
+
+		When written to, the value is cached and used to perform the
+		read operation. Allowed values are in the range 0 to N-1, where
+		N is the max number of ring pairs supported by a device. This
+		can be queried using the attribute qat/num_rps.
+
+		A read returns the service associated to the ring pair queried.
+
+		The values are:
+
+		* dc: the ring pair is configured for running compression services
+		* sym: the ring pair is configured for running symmetric crypto
+		  services
+		* asym: the ring pair is configured for running asymmetric crypto
+		  services
+
+		Example usage::
+
+			# echo 1 > /sys/bus/pci/devices/<BDF>/qat/rp2srv
+			# cat /sys/bus/pci/devices/<BDF>/qat/rp2srv
+			sym
+
+		This attribute is available for qat_4xxx and qat_6xxx devices.
+
+What:		/sys/bus/pci/devices/<BDF>/qat/num_rps
+Date:		January 2024
+KernelVersion:	6.7
+Contact:	qat-linux@intel.com
+Description:
+		(RO) Returns the number of ring pairs that a single device has.
+
+		Example usage::
+
+			# cat /sys/bus/pci/devices/<BDF>/qat/num_rps
+			64
+
+		This attribute is available for qat_4xxx and qat_6xxx devices.
+
+What:		/sys/bus/pci/devices/<BDF>/qat/auto_reset
+Date:		May 2024
+KernelVersion:	6.9
+Contact:	qat-linux@intel.com
+Description:	(RW) Reports the current state of the autoreset feature
+		for a QAT device
+
+		Write to the attribute to enable or disable device auto reset.
+
+		Device auto reset is disabled by default.
+
+		The values are:
+
+		* 1/Yy/on: auto reset enabled. If the device encounters an
+		  unrecoverable error, it will be reset automatically.
+		* 0/Nn/off: auto reset disabled. If the device encounters an
+		  unrecoverable error, it will not be reset.
+
+		This attribute is available for qat_4xxx and qat_6xxx devices.