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, 175 insertions, 0 deletions

diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux
new file mode 100644
index 000000000..fcae1e432
--- /dev/null
+++ b/scripts/Makefile.vmlinux
@@ -0,0 +1,175 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+PHONY := __default
+__default: vmlinux
+
+include include/config/auto.conf
+include $(srctree)/scripts/Kbuild.include
+include $(srctree)/scripts/Makefile.lib
+
+targets :=
+
+%.o: %.c FORCE
+	$(call if_changed_rule,cc_o_c)
+
+%.o: %.S FORCE
+	$(call if_changed_rule,as_o_S)
+
+# Built-in dtb
+# ---------------------------------------------------------------------------
+
+quiet_cmd_wrap_dtbs = WRAP    $@
+      cmd_wrap_dtbs = {							\
+	echo '\#include <asm-generic/vmlinux.lds.h>';			\
+	echo '.section .dtb.init.rodata,"a"';				\
+	while read dtb; do						\
+		symbase=__dtb_$$(basename -s .dtb "$${dtb}" | tr - _);	\
+		echo '.balign STRUCT_ALIGNMENT';			\
+		echo ".global $${symbase}_begin";			\
+		echo "$${symbase}_begin:";				\
+		echo '.incbin "'$$dtb'" ';				\
+		echo ".global $${symbase}_end";				\
+		echo "$${symbase}_end:";				\
+	done < $<;							\
+	} > $@
+
+.builtin-dtbs.S: .builtin-dtbs-list FORCE
+	$(call if_changed,wrap_dtbs)
+
+quiet_cmd_gen_dtbs_list = GEN     $@
+      cmd_gen_dtbs_list = \
+	$(if $(CONFIG_BUILTIN_DTB_NAME), echo "arch/$(SRCARCH)/boot/dts/$(CONFIG_BUILTIN_DTB_NAME).dtb",:) > $@
+
+.builtin-dtbs-list: arch/$(SRCARCH)/boot/dts/dtbs-list FORCE
+	$(call if_changed,$(if $(CONFIG_BUILTIN_DTB_ALL),copy,gen_dtbs_list))
+
+targets += .builtin-dtbs-list
+
+ifdef CONFIG_GENERIC_BUILTIN_DTB
+targets += .builtin-dtbs.S .builtin-dtbs.o
+vmlinux.unstripped: .builtin-dtbs.o
+endif
+
+# vmlinux.unstripped
+# ---------------------------------------------------------------------------
+
+ifdef CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX
+vmlinux.unstripped: arch/$(SRCARCH)/tools/vmlinux.arch.o
+
+arch/$(SRCARCH)/tools/vmlinux.arch.o: vmlinux.o FORCE
+	$(Q)$(MAKE) $(build)=arch/$(SRCARCH)/tools $@
+endif
+
+ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)
+
+# Final link of vmlinux with optional arch pass after final link
+cmd_link_vmlinux =							\
+	$< "$(LD)" "$(KBUILD_LDFLAGS)" "$(LDFLAGS_vmlinux)" "$@";	\
+	$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)
+
+targets += vmlinux.unstripped .vmlinux.export.o
+vmlinux.unstripped: scripts/link-vmlinux.sh vmlinux.o .vmlinux.export.o $(KBUILD_LDS) FORCE
+	+$(call if_changed_dep,link_vmlinux)
+ifdef CONFIG_DEBUG_INFO_BTF
+vmlinux.unstripped: $(RESOLVE_BTFIDS) $(srctree)/scripts/gen-btf.sh
+endif
+
+ifdef CONFIG_BUILDTIME_TABLE_SORT
+vmlinux.unstripped: scripts/sorttable
+endif
+
+# vmlinux
+# ---------------------------------------------------------------------------
+
+remove-section-y                                   := .modinfo
+remove-section-$(CONFIG_ARCH_VMLINUX_NEEDS_RELOCS) += '.rel*' '!.rel*.dyn'
+# for compatibility with binutils < 2.32
+# https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=c12d9fa2afe7abcbe407a00e15719e1a1350c2a7
+remove-section-$(CONFIG_ARCH_VMLINUX_NEEDS_RELOCS) += '.rel.*'
+
+remove-symbols := -w --strip-unneeded-symbol='__mod_device_table__*'
+
+# To avoid warnings: "empty loadable segment detected at ..." from GNU objcopy,
+# it is necessary to remove the PT_LOAD flag from the segment.
+quiet_cmd_strip_relocs = OBJCOPY $@
+      cmd_strip_relocs = $(OBJCOPY) $(patsubst %,--set-section-flags %=noload,$(remove-section-y)) $< $@; \
+                         $(OBJCOPY) $(addprefix --remove-section=,$(remove-section-y)) $(remove-symbols) $@
+
+targets += vmlinux
+vmlinux: vmlinux.unstripped FORCE
+	$(call if_changed,strip_relocs)
+
+# modules.builtin.modinfo
+# ---------------------------------------------------------------------------
+
+# .modinfo in vmlinux.unstripped is aligned to 8 bytes for compatibility with
+# tools that expect vmlinux to have sufficiently aligned sections but the
+# additional bytes used for padding .modinfo to satisfy this requirement break
+# certain versions of kmod with
+#
+#   depmod: ERROR: kmod_builtin_iter_next: unexpected string without modname prefix
+#
+# Strip the trailing padding bytes after extracting .modinfo to comply with
+# what kmod expects to parse.
+quiet_cmd_modules_builtin_modinfo = GEN     $@
+      cmd_modules_builtin_modinfo = $(cmd_objcopy); \
+                                    sed -i 's/\x00\+$$/\x00/g' $@; \
+                                    chmod -x $@
+
+OBJCOPYFLAGS_modules.builtin.modinfo := -j .modinfo -O binary
+
+targets += modules.builtin.modinfo
+modules.builtin.modinfo: vmlinux.unstripped FORCE
+	$(call if_changed,modules_builtin_modinfo)
+
+# modules.builtin
+# ---------------------------------------------------------------------------
+
+__default: modules.builtin
+
+# The second line aids cases where multiple modules share the same object.
+
+quiet_cmd_modules_builtin = GEN     $@
+      cmd_modules_builtin = \
+	tr '\0' '\n' < $< | \
+	sed -n 's/^[[:alnum:]:_]*\.file=//p' | \
+	tr ' ' '\n' | uniq | sed -e 's:^:kernel/:' -e 's/$$/.ko/' > $@
+
+targets += modules.builtin
+modules.builtin: modules.builtin.modinfo FORCE
+	$(call if_changed,modules_builtin)
+
+# modules.builtin.ranges
+# ---------------------------------------------------------------------------
+ifdef CONFIG_BUILTIN_MODULE_RANGES
+__default: modules.builtin.ranges
+
+quiet_cmd_modules_builtin_ranges = GEN     $@
+      cmd_modules_builtin_ranges = gawk -f $(real-prereqs) > $@
+
+targets += modules.builtin.ranges
+modules.builtin.ranges: $(srctree)/scripts/generate_builtin_ranges.awk \
+			modules.builtin vmlinux.map vmlinux.o.map FORCE
+	$(call if_changed,modules_builtin_ranges)
+
+vmlinux.map: vmlinux.unstripped
+	@:
+
+endif
+
+# Add FORCE to the prerequisites of a target to force it to be always rebuilt.
+# ---------------------------------------------------------------------------
+
+PHONY += FORCE
+FORCE:
+
+# Read all saved command lines and dependencies for the $(targets) we
+# may be building above, using $(if_changed{,_dep}). As an
+# optimization, we don't need to read them if the target does not
+# exist, we will rebuild anyway in that case.
+
+existing-targets := $(wildcard $(sort $(targets)))
+
+-include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
+
+.PHONY: $(PHONY)