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, 76 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-net-qmi b/Documentation/ABI/testing/sysfs-class-net-qmi
new file mode 100644
index 000000000..b028f5bc8
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-net-qmi
@@ -0,0 +1,76 @@
+What:		/sys/class/net/<iface>/qmi/raw_ip
+Date:		Dec 2015
+KernelVersion:	4.4
+Contact:	Bjørn Mork <bjorn@mork.no>
+Description:
+		Boolean.  Default: 'N'
+
+		Set this to 'Y' to change the network device link
+		framing from '802.3' to 'raw-ip'.
+
+		The netdev will change to reflect the link framing
+		mode.  The netdev is an ordinary ethernet device in
+		'802.3' mode, and the driver expects to exchange
+		frames with an ethernet header over the USB link. The
+		netdev is a headerless p-t-p device in 'raw-ip' mode,
+		and the driver expects to echange IPv4 or IPv6 packets
+		without any L2 header over the USB link.
+
+		Userspace is in full control of firmware configuration
+		through the delegation of the QMI protocol. Userspace
+		is responsible for coordination of driver and firmware
+		link framing mode, changing this setting to 'Y' if the
+		firmware is configured for 'raw-ip' mode.
+
+What:		/sys/class/net/<iface>/qmi/add_mux
+Date:		March 2017
+KernelVersion:	4.11
+Contact:	Bjørn Mork <bjorn@mork.no>
+Description:
+		Unsigned integer.
+
+		Write a number ranging from 1 to 254 to add a qmap mux
+		based network device, supported by recent Qualcomm based
+		modems.
+
+		The network device will be called qmimux.
+
+		Userspace is in charge of managing the qmux network device
+		activation and data stream setup on the modem side by
+		using the proper QMI protocol requests.
+
+What:		/sys/class/net/<iface>/qmi/del_mux
+Date:		March 2017
+KernelVersion:	4.11
+Contact:	Bjørn Mork <bjorn@mork.no>
+Description:
+		Unsigned integer.
+
+		Write a number ranging from 1 to 254 to delete a previously
+		created qmap mux based network device.
+
+What:		/sys/class/net/<qmimux iface>/qmap/mux_id
+Date:		January 2021
+KernelVersion:	5.12
+Contact:	Daniele Palmas <dnlplm@gmail.com>
+Description:
+		Unsigned integer
+
+		Indicates the mux id associated to the qmimux network interface
+		during its creation.
+
+What:		/sys/class/net/<iface>/qmi/pass_through
+Date:		January 2021
+KernelVersion:	5.12
+Contact:	Subash Abhinov Kasiviswanathan <quic_subashab@quicinc.com>
+Description:
+		Boolean.  Default: 'N'
+
+		Set this to 'Y' to enable 'pass-through' mode, allowing packets
+		in MAP format to be passed on to the stack.
+
+		Normally the rmnet driver (CONFIG_RMNET) is then used to process
+		and demultiplex these packets.
+
+		'Pass-through' mode can be enabled when the device is in
+		'raw-ip' mode only.