On Mon, 3 Aug 2026 at 18:59, Marc Zyngier <[email protected]> wrote:
...
> > +/*
> > + * Generate a typed stub for each declared hypercall. kvm_call_hyp_nvhe()
> > + * resolves to the stub, so a call with the wrong argument count or types
> > + * fails to compile instead of being silently truncated to an SMCCC
> > function
> > + * number and a pile of registers. The stub inlines to the same SMCCC call
> > + * the untyped macro used to make.
> > + */
> > +#define DECLARE_KVM_HOST_HCALL(ret, name, ...)
> > \
> > + static __always_inline \
> > + ret nvhe_hvc_##name(__KVM_HCALL_MAP(__KVM_HCALL_DECL, __VA_ARGS__)) \
> > + { \
> > + return (ret)__kvm_call_hyp_nvhe(name, \
> > + __KVM_HCALL_MAP(__KVM_HCALL_ARGS, __VA_ARGS__));\
> > + }
> > +
> > +#define DECLARE_KVM_HOST_HCALL_VOID(name, ...)
> > \
> > + static __always_inline \
> > + void nvhe_hvc_##name(__KVM_HCALL_MAP(__KVM_HCALL_DECL, __VA_ARGS__)) \
> > + { \
> > + __kvm_call_hyp_nvhe(name, \
> > + __KVM_HCALL_MAP(__KVM_HCALL_ARGS, __VA_ARGS__));\
> > + }
>
> I'll bite! ;-) void is a type, not the absence of a type. And
> returning void is perfectly valid.
>
> So with this in mind, I got rid of the *_VOID() helpers altogether,
> see below.
This looks better. I've built and boot tested it, and the generated
code is identical.
I noticed is that gcc and clang complain about "return (void)expr"
under -Wpedantic, since ISO C only allows it from C23. We never build
with that, right? So it doesn't bite ;)
Cheers,
/fuad
>
> Thanks,
>
> M.
>
> diff --git a/arch/arm64/include/asm/kvm_hcall.h
> b/arch/arm64/include/asm/kvm_hcall.h
> index 3958396a83345..0b1b10d4212da 100644
> --- a/arch/arm64/include/asm/kvm_hcall.h
> +++ b/arch/arm64/include/asm/kvm_hcall.h
> @@ -88,26 +88,12 @@ struct vgic_v5_cpu_if;
> __KVM_HCALL_MAP(__KVM_HCALL_ARGS, __VA_ARGS__));\
> }
>
> -#define DECLARE_KVM_HOST_HCALL_VOID(name, ...) \
> - static __always_inline \
> - void nvhe_hvc_##name(__KVM_HCALL_MAP(__KVM_HCALL_DECL, __VA_ARGS__)) \
> - { \
> - __kvm_call_hyp_nvhe(name, \
> - __KVM_HCALL_MAP(__KVM_HCALL_ARGS, __VA_ARGS__));\
> - }
> -
> #define DECLARE_KVM_HOST_HCALL0(ret, name) \
> static __always_inline ret nvhe_hvc_##name(void) \
> { \
> return (ret)__kvm_call_hyp_nvhe(name); \
> }
>
> -#define DECLARE_KVM_HOST_HCALL0_VOID(name) \
> - static __always_inline void nvhe_hvc_##name(void) \
> - { \
> - __kvm_call_hyp_nvhe(name); \
> - }
> -
> #define kvm_call_hyp_nvhe(f, ...) nvhe_hvc_##f(__VA_ARGS__)
>
> /*
> @@ -148,12 +134,8 @@ struct vgic_v5_cpu_if;
> */
> #define DECLARE_KVM_HOST_HCALL(ret, name, ...) \
> typedef ret
> kvm_host_hcall_sig_##name(__KVM_HCALL_MAP(__KVM_HCALL_DECL, __VA_ARGS__));
> -#define DECLARE_KVM_HOST_HCALL_VOID(name, ...) \
> - typedef void
> kvm_host_hcall_sig_##name(__KVM_HCALL_MAP(__KVM_HCALL_DECL, __VA_ARGS__));
> #define DECLARE_KVM_HOST_HCALL0(ret, name) \
> typedef ret kvm_host_hcall_sig_##name(void);
> -#define DECLARE_KVM_HOST_HCALL0_VOID(name) \
> - typedef void kvm_host_hcall_sig_##name(void);
> #endif /* __KVM_NVHE_HYPERVISOR__ */
>
> /* Hypercalls that are unavailable once pKVM has finalised. */
> @@ -164,52 +146,52 @@ DECLARE_KVM_HOST_HCALL(unsigned long,
> __pkvm_create_private_mapping,
> phys_addr_t, phys, size_t, size, u64, prot)
> DECLARE_KVM_HOST_HCALL(int, __pkvm_cpu_set_vector,
> enum arm64_hyp_spectre_vector, slot)
> -DECLARE_KVM_HOST_HCALL0_VOID(__kvm_enable_ssbs)
> -DECLARE_KVM_HOST_HCALL0_VOID(__vgic_v3_init_lrs)
> +DECLARE_KVM_HOST_HCALL0(void, __kvm_enable_ssbs)
> +DECLARE_KVM_HOST_HCALL0(void, __vgic_v3_init_lrs)
> DECLARE_KVM_HOST_HCALL0(u64, __vgic_v3_get_gic_config)
>
> DECLARE_KVM_HOST_HCALL0(int, __pkvm_prot_finalize)
>
> /* Hypercalls that are always available and common to [nh]VHE/pKVM. */
> -DECLARE_KVM_HOST_HCALL_VOID(__kvm_adjust_pc,
> +DECLARE_KVM_HOST_HCALL(void, __kvm_adjust_pc,
> struct kvm_vcpu __kern *, vcpu)
> DECLARE_KVM_HOST_HCALL(int, __kvm_vcpu_run,
> struct kvm_vcpu __kern *, vcpu)
> -DECLARE_KVM_HOST_HCALL0_VOID(__kvm_flush_vm_context)
> -DECLARE_KVM_HOST_HCALL_VOID(__kvm_tlb_flush_vmid_ipa,
> +DECLARE_KVM_HOST_HCALL0(void, __kvm_flush_vm_context)
> +DECLARE_KVM_HOST_HCALL(void, __kvm_tlb_flush_vmid_ipa,
> struct kvm_s2_mmu __kern *, mmu, phys_addr_t, ipa, int, level)
> -DECLARE_KVM_HOST_HCALL_VOID(__kvm_tlb_flush_vmid_ipa_nsh,
> +DECLARE_KVM_HOST_HCALL(void, __kvm_tlb_flush_vmid_ipa_nsh,
> struct kvm_s2_mmu __kern *, mmu, phys_addr_t, ipa, int, level)
> -DECLARE_KVM_HOST_HCALL_VOID(__kvm_tlb_flush_vmid,
> +DECLARE_KVM_HOST_HCALL(void, __kvm_tlb_flush_vmid,
> struct kvm_s2_mmu __kern *, mmu)
> -DECLARE_KVM_HOST_HCALL_VOID(__kvm_tlb_flush_vmid_range,
> +DECLARE_KVM_HOST_HCALL(void, __kvm_tlb_flush_vmid_range,
> struct kvm_s2_mmu __kern *, mmu, phys_addr_t, start, unsigned long,
> pages)
> -DECLARE_KVM_HOST_HCALL_VOID(__kvm_flush_cpu_context,
> +DECLARE_KVM_HOST_HCALL(void, __kvm_flush_cpu_context,
> struct kvm_s2_mmu __kern *, mmu)
> -DECLARE_KVM_HOST_HCALL_VOID(__kvm_timer_set_cntvoff,
> +DECLARE_KVM_HOST_HCALL(void, __kvm_timer_set_cntvoff,
> u64, cntvoff)
> DECLARE_KVM_HOST_HCALL(int, __tracing_load,
> void __kern *, desc_hva, size_t, desc_size)
> -DECLARE_KVM_HOST_HCALL0_VOID(__tracing_unload)
> +DECLARE_KVM_HOST_HCALL0(void, __tracing_unload)
> DECLARE_KVM_HOST_HCALL(int, __tracing_enable,
> bool, enable)
> DECLARE_KVM_HOST_HCALL(int, __tracing_swap_reader,
> unsigned int, cpu)
> -DECLARE_KVM_HOST_HCALL_VOID(__tracing_update_clock,
> +DECLARE_KVM_HOST_HCALL(void, __tracing_update_clock,
> u32, mult, u32, shift, u64, epoch_ns, u64, epoch_cyc)
> DECLARE_KVM_HOST_HCALL(int, __tracing_reset,
> unsigned int, cpu)
> DECLARE_KVM_HOST_HCALL(int, __tracing_enable_event,
> unsigned short, id, bool, enable)
> -DECLARE_KVM_HOST_HCALL_VOID(__tracing_write_event,
> +DECLARE_KVM_HOST_HCALL(void, __tracing_write_event,
> u64, id)
> -DECLARE_KVM_HOST_HCALL_VOID(__vgic_v3_save_aprs,
> +DECLARE_KVM_HOST_HCALL(void, __vgic_v3_save_aprs,
> struct vgic_v3_cpu_if __kern *, cpu_if)
> -DECLARE_KVM_HOST_HCALL_VOID(__vgic_v3_restore_vmcr_aprs,
> +DECLARE_KVM_HOST_HCALL(void, __vgic_v3_restore_vmcr_aprs,
> struct vgic_v3_cpu_if __kern *, cpu_if)
> -DECLARE_KVM_HOST_HCALL_VOID(__vgic_v5_save_apr,
> +DECLARE_KVM_HOST_HCALL(void, __vgic_v5_save_apr,
> struct vgic_v5_cpu_if __kern *, cpu_if)
> -DECLARE_KVM_HOST_HCALL_VOID(__vgic_v5_restore_vmcr_apr,
> +DECLARE_KVM_HOST_HCALL(void, __vgic_v5_restore_vmcr_apr,
> struct vgic_v5_cpu_if __kern *, cpu_if)
>
> /* Hypercalls that are available only when pKVM has finalised. */
> @@ -232,7 +214,7 @@ DECLARE_KVM_HOST_HCALL(int,
> __pkvm_host_test_clear_young_guest,
> DECLARE_KVM_HOST_HCALL(int, __pkvm_host_mkyoung_guest,
> u64, gfn)
> DECLARE_KVM_HOST_HCALL0(int, __pkvm_reserve_vm)
> -DECLARE_KVM_HOST_HCALL_VOID(__pkvm_unreserve_vm,
> +DECLARE_KVM_HOST_HCALL(void, __pkvm_unreserve_vm,
> pkvm_handle_t, handle)
> DECLARE_KVM_HOST_HCALL(int, __pkvm_init_vm,
> struct kvm __kern *, host_kvm, void __kern *, vm_hva,
> @@ -249,10 +231,10 @@ DECLARE_KVM_HOST_HCALL(int, __pkvm_start_teardown_vm,
> pkvm_handle_t, handle)
> DECLARE_KVM_HOST_HCALL(int, __pkvm_finalize_teardown_vm,
> pkvm_handle_t, handle)
> -DECLARE_KVM_HOST_HCALL_VOID(__pkvm_vcpu_load,
> +DECLARE_KVM_HOST_HCALL(void, __pkvm_vcpu_load,
> pkvm_handle_t, handle, unsigned int, vcpu_idx, u64, hcr_el2)
> -DECLARE_KVM_HOST_HCALL0_VOID(__pkvm_vcpu_put)
> -DECLARE_KVM_HOST_HCALL_VOID(__pkvm_tlb_flush_vmid,
> +DECLARE_KVM_HOST_HCALL0(void, __pkvm_vcpu_put)
> +DECLARE_KVM_HOST_HCALL(void, __pkvm_tlb_flush_vmid,
> pkvm_handle_t, handle)
>
> #endif /* __ARM64_KVM_HCALL_H__ */
>
> --
> Without deviation from the norm, progress is not possible.
