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, 19 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/procfs-attr-prev b/Documentation/ABI/testing/procfs-attr-prev
new file mode 100644
index 000000000..f990b3595
--- /dev/null
+++ b/Documentation/ABI/testing/procfs-attr-prev
@@ -0,0 +1,19 @@
+What:		/proc/*/attr/prev
+Contact:	linux-security-module@vger.kernel.org,
+		selinux@vger.kernel.org,
+		apparmor@lists.ubuntu.com
+Description:	The security information used on the process by
+		a Linux security module (LSM) active on the system
+		prior to the most recent exec() call.
+		The details of permissions required to read from
+		this interface is LSM dependent.
+		A process cannot write to this interface unless it
+		refers to itself.
+		The other details of permissions required to write to
+		this interface are LSM dependent.
+		The format of the data used by this interface is LSM
+		dependent.
+		SELinux and AppArmor provide this interface.
+Users:		SELinux user-space
+		AppArmor user-space
+