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, 56 insertions, 0 deletions

diff --git a/arch/arm/vdso/Makefile b/arch/arm/vdso/Makefile
new file mode 100644
index 000000000..cf8cd39ab
--- /dev/null
+++ b/arch/arm/vdso/Makefile
@@ -0,0 +1,56 @@
+# SPDX-License-Identifier: GPL-2.0
+
+# Include the generic Makefile to check the built vdso.
+include $(srctree)/lib/vdso/Makefile.include
+
+hostprogs := vdsomunge
+
+obj-vdso := vgettimeofday.o note.o
+
+# Build rules
+targets := $(obj-vdso) vdso.so vdso.so.dbg vdso.so.raw vdso.lds
+obj-vdso := $(addprefix $(obj)/, $(obj-vdso))
+
+ccflags-y := -fPIC -fno-common -fno-builtin -fno-stack-protector
+ccflags-y += -DDISABLE_BRANCH_PROFILING -DBUILD_VDSO32
+
+ldflags-$(CONFIG_CPU_ENDIAN_BE8) := --be8
+ldflags-y := -Bsymbolic --no-undefined -soname=linux-vdso.so.1 \
+	    -z max-page-size=4096 -shared $(ldflags-y) \
+	    --hash-style=sysv --build-id=sha1 \
+	    -T
+
+obj-$(CONFIG_VDSO) += vdso.o
+CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
+
+CFLAGS_REMOVE_vdso.o = -pg
+
+# Force -O2 to avoid libgcc dependencies
+CFLAGS_REMOVE_vgettimeofday.o = -pg -Os $(RANDSTRUCT_CFLAGS) $(KSTACK_ERASE_CFLAGS) $(GCC_PLUGINS_CFLAGS)
+ifeq ($(c-gettimeofday-y),)
+CFLAGS_vgettimeofday.o = -O2
+else
+CFLAGS_vgettimeofday.o = -O2 -include $(c-gettimeofday-y)
+endif
+
+# Force dependency
+$(obj)/vdso.o : $(obj)/vdso.so
+
+# Link rule for the .so file
+$(obj)/vdso.so.raw: $(obj)/vdso.lds $(obj-vdso) FORCE
+	$(call if_changed,vdsold_and_vdso_check)
+
+$(obj)/vdso.so.dbg: $(obj)/vdso.so.raw $(obj)/vdsomunge FORCE
+	$(call if_changed,vdsomunge)
+
+# Strip rule for the .so file
+$(obj)/%.so: OBJCOPYFLAGS := -S
+$(obj)/%.so: $(obj)/%.so.dbg FORCE
+	$(call if_changed,objcopy)
+
+# Actual build commands
+quiet_cmd_vdsold_and_vdso_check = LD      $@
+      cmd_vdsold_and_vdso_check = $(cmd_ld); $(cmd_vdso_check)
+
+quiet_cmd_vdsomunge = MUNGE   $@
+      cmd_vdsomunge = $(objtree)/$(obj)/vdsomunge $< $@