Subject: [PATCH v2 28/28] KVM: s390: arm64: Enable KVM_ARM64 config and Kbuild

From: Steffen Eiden <[email-masked]>
Date: Tue, 28 Apr 2026 17:56:20 +0200

Add all Kbuild/Makefile configurations to build a second KVM module on
s390 implementing the arm64-KVM API. To prevent symbol conflicts with
kvm-s390 all internal symbols in kvm-arm64 are mangled if compiled as
built-in. The new module ins named kvm-arm64.

As in this case the build does not go through the normal build process
the module parameter handling would be messed up. By forcing
KBUILD_MODNAME to kvm-arm64 all parameters are at the same location and
not at object/basename of the object file the parameter is introduced.

Co-developed-by: Andreas Grapentin <[email-masked]>
Signed-off-by: Andreas Grapentin <[email-masked]>
Co-developed-by: Nina Schoetterl-Glausch <[email-masked]>
Signed-off-by: Nina Schoetterl-Glausch <[email-masked]>
Co-developed-by: Gautam Gala <[email-masked]>
Signed-off-by: Gautam Gala <[email-masked]>
Signed-off-by: Steffen Eiden <[email-masked]>
---
 arch/s390/configs/defconfig  |   1 +
 arch/s390/include/asm/Kbuild |   3 +
 arch/s390/kvm/Kconfig        |   1 +
 arch/s390/kvm/Makefile       |   1 +
 arch/s390/kvm/arm64/Kconfig  |  21 +++++++
 arch/s390/kvm/arm64/Makefile | 108 +++++++++++++++++++++++++++++++++++
 arch/s390/kvm/s390/Kconfig   |   1 -
 arch/s390/tools/Makefile     |   2 +
 8 files changed, 137 insertions(+), 1 deletion(-)
 create mode 100644 arch/s390/kvm/arm64/Kconfig
 create mode 100644 arch/s390/kvm/arm64/Makefile

diff --git a/arch/s390/configs/defconfig b/arch/s390/configs/defconfig
index bbbb4d0df9dd..e10e9e1ad94d 100644
--- a/arch/s390/configs/defconfig
+++ b/arch/s390/configs/defconfig
@@ -58,6 +58,7 @@ CONFIG_CMM=m
 CONFIG_APPLDATA_BASE=y
 CONFIG_S390_HYPFS_FS=y
 CONFIG_KVM_S390=m
+CONFIG_KVM_ARM64=m
 CONFIG_S390_UNWIND_SELFTEST=m
 CONFIG_S390_KPROBES_SANITY_TEST=m
 CONFIG_S390_MODULES_SANITY_TEST=m
diff --git a/arch/s390/include/asm/Kbuild b/arch/s390/include/asm/Kbuild
index 80bad7de7a04..c2c238f418c6 100644
--- a/arch/s390/include/asm/Kbuild
+++ b/arch/s390/include/asm/Kbuild
@@ -7,3 +7,6 @@ generated-y += unistd_nr.h
 generic-y += asm-offsets.h
 generic-y += mcs_spinlock.h
 generic-y += mmzone.h
+
+generated-y += sysreg-gen-defs.h
+generated-y += kvm_arm64_modname.h
diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig
index f8d4a9a38dae..bbae58aa8bc4 100644
--- a/arch/s390/kvm/Kconfig
+++ b/arch/s390/kvm/Kconfig
@@ -20,5 +20,6 @@ config KVM
 	tristate
 
 source "arch/s390/kvm/s390/Kconfig"
+source "arch/s390/kvm/arm64/Kconfig"
 
 endif # VIRTUALIZATION
diff --git a/arch/s390/kvm/Makefile b/arch/s390/kvm/Makefile
index c43d7dffca13..38bdd7c9b42d 100644
--- a/arch/s390/kvm/Makefile
+++ b/arch/s390/kvm/Makefile
@@ -4,3 +4,4 @@
 # Copyright IBM Corp. 2008
 
 obj-$(CONFIG_KVM_S390) += s390/
+obj-$(CONFIG_KVM_ARM64) += arm64/
diff --git a/arch/s390/kvm/arm64/Kconfig b/arch/s390/kvm/arm64/Kconfig
new file mode 100644
index 000000000000..42a1be50f6e1
--- /dev/null
+++ b/arch/s390/kvm/arm64/Kconfig
@@ -0,0 +1,21 @@
+# SPDX-License-Identifier: GPL-2.0
+
+config KVM_ARM64
+	def_tristate y
+	prompt "Kernel-based Virtual Machine (KVM) support for arm64 guests"
+	select KVM
+	select KVM_VFIO
+	select IRQ_BYPASS_MANAGER
+	select SCHED_INFO
+	select XARRAY_MULTI
+	select KVM_COMMON
+	select HAVE_KVM_CPU_RELAX_INTERCEPT
+	select HAVE_KVM_MSI
+	select HAVE_KVM_IRQCHIP
+	select HAVE_KVM_IRQ_ROUTING
+	select HAVE_KVM_VCPU_RUN_PID_CHANGE
+	select GUEST_PERF_EVENTS if PERF_EVENTS
+	help
+	  Support hosting virtualized arm64 guest machines on s390 host machines.
+
+	  If unsure, say N.
diff --git a/arch/s390/kvm/arm64/Makefile b/arch/s390/kvm/arm64/Makefile
new file mode 100644
index 000000000000..d0aac34b8d2f
--- /dev/null
+++ b/arch/s390/kvm/arm64/Makefile
@@ -0,0 +1,108 @@
+# SPDX-License-Identifier: GPL-2.0
+
+KVM := ../../../../virt/kvm
+include $(srctree)/virt/kvm/Makefile.kvm
+include $(srctree)/virt/kvm/arm64/Makefile.kvm
+include $(srctree)/arch/s390/kvm/gmap/Makefile
+
+ccflags-y += -I $(src) -I$(srctree)/arch/s390/kvm/gmap -DKVM_S390_ARM64
+
+kvm-arm64-obj := \
+	arm.o \
+	guest.o \
+	handle_exit.o \
+	inject_fault.o \
+	mmu.o \
+	reset.o \
+
+kvm-arm64-obj += $(patsubst %.o,%-arm64.o,$(shared-arm64-obj))
+kvm-arm64-obj += $(patsubst %.o,%-arm64.o,$(kvm-y))
+
+targets += $(kvm-arm64-obj)
+
+$(obj)/%-arm64.o: $(src)/%.c FORCE
+	@mkdir -p $(dir $@)
+	$(call if_changed_rule,cc_o_c)
+
+ifeq ($(CONFIG_KVM_ARM64),m)
+
+kvm-arm64-y = $(kvm-arm64-obj)
+
+else ifeq ($(CONFIG_KVM_ARM64),y)
+
+KVM_ARM64_GEN_DIR :=$(objtree)/arch/${SRCARCH}/include/generated/asm
+KVM_ARM64_MODNAME_H := $(KVM_ARM64_GEN_DIR)/kvm_arm64_modname.h
+ccflags-y += -include $(KVM_ARM64_MODNAME_H)
+
+targets += $(KVM_ARM64_MODNAME_H)
+
+quiet_cmd_kvm_arm64_modname_h = GEN     $@
+      cmd_kvm_arm64_modname_h = { \
+	echo '/* Automatically generated; do not edit. */'; \
+	echo '\#ifndef _KVM_ARM64_MODNAME_H'; \
+	echo '\#define _KVM_ARM64_MODNAME_H'; \
+	echo '\#undef KBUILD_MODNAME'; \
+	echo '\#define KBUILD_MODNAME "kvm_arm64"'; \
+	echo '\#endif /* _KVM_ARM64_MODNAME_H */'; \
+	} > $@
+
+$(addprefix $(obj)/,$(kvm-arm64-obj)): $(KVM_ARM64_MODNAME_H)
+
+$(KVM_ARM64_MODNAME_H):
+	@mkdir -p $(KVM_ARM64_GEN_DIR)
+	$(call cmd,kvm_arm64_modname_h)
+
+prereq-o-cmd = $(foreach o, $(filter %.o, $^), $(dir $(o)).$(notdir $(o)).cmd)
+cmd_gen_symversions_o = \
+	grep --no-filename "^\#SYMVER" $(prereq-o-cmd) >> $(dot-target).cmd || true
+
+define rule_ld_o_o
+	$(call cmd_and_savecmd,ld)
+	$(call cmd,gen_symversions_o)
+endef
+
+LDFLAGS_kvm-unnamespaced.o := -r
+$(obj)/kvm-unnamespaced.o: $(addprefix $(obj)/,$(kvm-arm64-obj)) FORCE
+	$(call if_changed_rule,ld_o_o)
+
+# Make list of symbols to localize.
+# Collect normal/exported symbols. Use dict as set for deduplication.
+quiet_cmd_nm_filter = NMFLTR  $@
+	cmd_nm_filter = \
+$(NM) -jU $< | awk '							\
+{	if (match($$0, /^__export_symbol_(.*)$$/, exp_sym)) {		\
+		exp_syms[exp_sym[1]] = 1;				\
+	} else {							\
+		normal_syms[$$0] = 1;					\
+	}								\
+}									\
+END {									\
+	for (sym in normal_syms) {					\
+		if (!(sym in exp_syms)) {				\
+			print sym;					\
+		}							\
+	}								\
+}' > $@
+
+$(obj)/kvm_symbol_list: $(obj)/kvm-unnamespaced.o FORCE
+	$(call if_changed,nm_filter)
+
+define rule_oc_o_o
+	$(call cmd_and_savecmd,objcopy)
+	$(call cmd,gen_objtooldep)
+	$(call cmd,gen_symversions_o)
+endef
+
+OBJCOPYFLAGS_kvm-namespaced.o := -O default --localize-symbols=$(obj)/kvm_symbol_list
+$(obj)/kvm-namespaced.o: $(obj)/kvm-unnamespaced.o $(obj)/kvm_symbol_list FORCE
+	$(call if_changed_rule,oc_o_o)
+
+kvm-arm64-y = kvm-namespaced.o
+
+targets += kvm-unnamespaced.o kvm_symbol_list kvm-namespaced.o
+
+endif
+
+obj-$(CONFIG_KVM_ARM64) += kvm-arm64.o
+
+LINUXINCLUDE := -I$(srctree)/include/arch/arm64/ $(LINUXINCLUDE)
diff --git a/arch/s390/kvm/s390/Kconfig b/arch/s390/kvm/s390/Kconfig
index f9853e61fd58..263ff29b9c9c 100644
--- a/arch/s390/kvm/s390/Kconfig
+++ b/arch/s390/kvm/s390/Kconfig
@@ -2,7 +2,6 @@
 #
 # KVM_S390 configuration
 #
-source "virt/kvm/Kconfig"
 
 config KVM_S390
 	def_tristate y
diff --git a/arch/s390/tools/Makefile b/arch/s390/tools/Makefile
index f2862364fb42..921261dcde28 100644
--- a/arch/s390/tools/Makefile
+++ b/arch/s390/tools/Makefile
@@ -6,6 +6,8 @@
 kapi := arch/$(ARCH)/include/generated/asm
 kapi-hdrs-y := $(kapi)/facility-defs.h $(kapi)/dis-defs.h
 
+include $(srctree)/arch/arm64/tools/Makefile.sysreg
+
 PHONY += kapi
 
 kapi:	$(kapi-hdrs-y)
-- 
2.51.0