Re: [PATCH v5 31/31] KVM: s390: arm64: Enable KVM_ARM64 config and Kbuild

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [Low] The namespace-mangling logic for built-in compilation (CONFIG_KVM_ARM64=y) uses invalid toolchain flags and incorrectly localizes exported symbols, breaking the build.
- [Low] Duplicate exported symbols cause a fatal modpost failure when both KVM modules are compiled as loadable modules (CONFIG_KVM_ARM64=m and CONFIG_KVM_S390=m).
--

--- Patch [31]: [PATCH v5 31/31] KVM: s390: arm64: Enable KVM_ARM64 config and Kbuild ---
commit c83e4eeb21e3c1207840240024b39a24634ecae4
Author: Steffen Eiden <seiden@linux.ibm.com>

KVM: s390: arm64: Enable KVM_ARM64 config and Kbuild

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.

> diff --git a/arch/s390/kvm/arm64/Makefile b/arch/s390/kvm/arm64/Makefile
> new file mode 100644
> index 0000000000000..a102c35664cae
> --- /dev/null
> +++ b/arch/s390/kvm/arm64/Makefile
[ ... ]
> +ifeq ($(CONFIG_KVM_ARM64),m)
> +
> +kvm-arm64-y = $(kvm-arm64-obj)

[Severity: Low]
Does this module build lead to identical global exported symbols?

If both CONFIG_KVM_ARM64=m and CONFIG_KVM_S390=m are selected, both modules
include the core virt/kvm files without symbol localization, which causes a
fatal modpost failure due to duplicate EXPORT_SYMBOL definitions.

> +
> +else ifeq ($(CONFIG_KVM_ARM64),y)
[ ... ]
> +quiet_cmd_nm_filter = NMFLTR  $@
> +	cmd_nm_filter = $(NM) -jU $< | sort -u > $@

[Severity: Low]
Are the -jU flags supported by GNU nm? Using unsupported flags causes a
fatal build error here.

> +
> +$(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

[Severity: Low]
Is -O default a valid objcopy flag?

Additionally, does this incorrectly localize exported symbols? This breaks
the build by causing modpost to abort.

> +$(obj)/kvm-namespaced.o: $(obj)/kvm-unnamespaced.o $(obj)/kvm_symbol_list FORCE
> +	$(call if_changed_rule,oc_o_o)

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260731130902.654679-1-seiden@linux.ibm.com?part=31