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, 25 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-kernel-btf b/Documentation/ABI/testing/sysfs-kernel-btf
new file mode 100644
index 000000000..fe96efdc9
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-btf
@@ -0,0 +1,25 @@
+What:		/sys/kernel/btf
+Date:		Aug 2019
+KernelVersion:	5.5
+Contact:	bpf@vger.kernel.org
+Description:
+		Contains BTF type information and related data for kernel and
+		kernel modules.
+
+What:		/sys/kernel/btf/vmlinux
+Date:		Aug 2019
+KernelVersion:	5.5
+Contact:	bpf@vger.kernel.org
+Description:
+		Read-only binary attribute exposing kernel's own BTF type
+		information with description of all internal kernel types. See
+		Documentation/bpf/btf.rst for detailed description of format
+		itself.
+
+What:		/sys/kernel/btf/<module-name>
+Date:		Nov 2020
+KernelVersion:	5.11
+Contact:	bpf@vger.kernel.org
+Description:
+		Read-only binary attribute exposing kernel module's BTF type
+		information as an add-on to the kernel's BTF (/sys/kernel/btf/vmlinux).