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, 33 insertions, 0 deletions

diff --git a/arch/arm/tools/syscallnr.sh b/arch/arm/tools/syscallnr.sh
new file mode 100644
index 000000000..9e386770b
--- /dev/null
+++ b/arch/arm/tools/syscallnr.sh
@@ -0,0 +1,33 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+in="$1"
+out="$2"
+align=1
+
+fileguard=_ASM_ARM_`basename "$out" | sed \
+    -e 'y/abcdefghijklmnopqrstuvwxyz/ABCDEFGHIJKLMNOPQRSTUVWXYZ/' \
+    -e 's/[^A-Z0-9_]/_/g' -e 's/__/_/g'`
+
+grep -E "^[0-9A-Fa-fXx]+[[:space:]]+" "$in" | sort -n | tail -n1 | (
+    echo "#ifndef ${fileguard}
+#define ${fileguard} 1
+
+/*
+ * This needs to be greater than __NR_last_syscall+1 in order to account
+ * for the padding in the syscall table.
+ */
+"
+
+    while read nr abi name entry; do
+        nr=$(($nr + 1))
+        while [ "$(($nr / (256 * $align) ))" -gt 0 ]; do
+            align=$(( $align * 4 ))
+        done
+        nr=$(( ($nr + $align - 1) & ~($align - 1) ))
+        echo "/* aligned to $align */"
+        echo "#define __NR_syscalls $nr"
+    done
+
+    echo ""
+    echo "#endif /* ${fileguard} */"
+) > "$out"