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, 45 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/debugfs-wilco-ec b/Documentation/ABI/testing/debugfs-wilco-ec
new file mode 100644
index 000000000..682e3c09e
--- /dev/null
+++ b/Documentation/ABI/testing/debugfs-wilco-ec
@@ -0,0 +1,45 @@
+What:		/sys/kernel/debug/wilco_ec/h1_gpio
+Date:		April 2019
+KernelVersion:	5.2
+Description:
+		As part of Chrome OS's FAFT (Fully Automated Firmware Testing)
+		tests, we need to ensure that the H1 chip is properly setting
+		some GPIO lines. The h1_gpio attribute exposes the state
+		of the lines:
+		- ENTRY_TO_FACT_MODE in BIT(0)
+		- SPI_CHROME_SEL in BIT(1)
+
+		Output will formatted with "0x%02x\n".
+
+What:		/sys/kernel/debug/wilco_ec/raw
+Date:		January 2019
+KernelVersion:	5.1
+Description:
+		Write and read raw mailbox commands to the EC.
+
+		You can write a hexadecimal sentence to raw, and that series of
+		bytes will be sent to the EC. Then, you can read the bytes of
+		response by reading from raw.
+
+		For writing, bytes 0-1 indicate the message type, one of enum
+		wilco_ec_msg_type. Byte 2+ consist of the data passed in the
+		request, starting at MBOX[0]. At least three bytes are required
+		for writing, two for the type and at least a single byte of
+		data.
+
+		Example::
+
+		    // Request EC info type 3 (EC firmware build date)
+		    // Corresponds with sending type 0x00f0 with
+		    // MBOX = [38, 00, 03, 00]
+		    $ echo 00 f0 38 00 03 00 > /sys/kernel/debug/wilco_ec/raw
+		    // View the result. The decoded ASCII result "12/21/18" is
+		    // included after the raw hex.
+		    // Corresponds with MBOX = [00, 00, 31, 32, 2f, 32, 31, 38, ...]
+		    $ cat /sys/kernel/debug/wilco_ec/raw
+		    00 00 31 32 2f 32 31 2f 31 38 00 38 00 01 00 2f 00  ..12/21/18.8...
+
+		Note that the first 16 bytes of the received MBOX[] will be
+		printed, even if some of the data is junk, and skipping bytes
+		17 to 32. It is up to you to know how many of the first bytes of
+		data are the actual response.