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, 40 insertions, 0 deletions

diff --git a/arch/arm64/tools/gen-cpucaps.awk b/arch/arm64/tools/gen-cpucaps.awk
new file mode 100755
index 000000000..2f4f61a0a
--- /dev/null
+++ b/arch/arm64/tools/gen-cpucaps.awk
@@ -0,0 +1,40 @@
+#!/bin/awk -f
+# SPDX-License-Identifier: GPL-2.0
+# gen-cpucaps.awk: arm64 cpucaps header generator
+#
+# Usage: awk -f gen-cpucaps.awk cpucaps.txt
+
+# Log an error and terminate
+function fatal(msg) {
+	print "Error at line " NR ": " msg > "/dev/stderr"
+	exit 1
+}
+
+# skip blank lines and comment lines
+/^$/ { next }
+/^#/ { next }
+
+BEGIN {
+	print "#ifndef __ASM_CPUCAP_DEFS_H"
+	print "#define __ASM_CPUCAP_DEFS_H"
+	print ""
+	print "/* Generated file - do not edit */"
+	cap_num = 0
+	print ""
+}
+
+/^[vA-Z0-9_]+$/ {
+	printf("#define ARM64_%-40s\t%d\n", $0, cap_num++)
+	next
+}
+
+END {
+	printf("#define ARM64_NCAPS\t\t\t\t\t%d\n", cap_num)
+	print ""
+	print "#endif /* __ASM_CPUCAP_DEFS_H */"
+}
+
+# Any lines not handled by previous rules are unexpected
+{
+	fatal("unhandled statement")
+}