Re: [PATCH v3 04/15] KVM: SVM: Compile sev.c if and only if CONFIG_KVM_AMD_SEV=y

[Isaku Yamahata]

On Mon, Feb 26, 2024 at 02:03:33PM -0500,
Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:

> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index 8ef95139cd24..52bc955ed06f 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -664,13 +664,10 @@ void avic_refresh_virtual_apic_mode(struct kvm_vcpu *vcpu);
>  
>  /* sev.c */
>  
> +#ifdef CONFIG_KVM_AMD_SEV
>  #define GHCB_VERSION_MAX	1ULL
>  #define GHCB_VERSION_MIN	1ULL
>  
> -
> -extern unsigned int max_sev_asid;
> -
> -void sev_vm_destroy(struct kvm *kvm);
>  int sev_mem_enc_ioctl(struct kvm *kvm, void __user *argp);
>  int sev_mem_enc_register_region(struct kvm *kvm,
>  				struct kvm_enc_region *range);
> @@ -681,19 +678,30 @@ int sev_vm_move_enc_context_from(struct kvm *kvm, unsigned int source_fd);
>  void sev_guest_memory_reclaimed(struct kvm *kvm);
>  
>  void pre_sev_run(struct vcpu_svm *svm, int cpu);
> -void __init sev_set_cpu_caps(void);
> -void __init sev_hardware_setup(void);
> -void sev_hardware_unsetup(void);
> -int sev_cpu_init(struct svm_cpu_data *sd);
>  void sev_init_vmcb(struct vcpu_svm *svm);
>  void sev_vcpu_after_set_cpuid(struct vcpu_svm *svm);
> -void sev_free_vcpu(struct kvm_vcpu *vcpu);
>  int sev_handle_vmgexit(struct kvm_vcpu *vcpu);
>  int sev_es_string_io(struct vcpu_svm *svm, int size, unsigned int port, int in);
>  void sev_es_vcpu_reset(struct vcpu_svm *svm);
>  void sev_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector);
>  void sev_es_prepare_switch_to_guest(struct sev_es_save_area *hostsa);
>  void sev_es_unmap_ghcb(struct vcpu_svm *svm);
> +void sev_free_vcpu(struct kvm_vcpu *vcpu);
> +void sev_vm_destroy(struct kvm *kvm);
> +void __init sev_set_cpu_caps(void);
> +void __init sev_hardware_setup(void);
> +void sev_hardware_unsetup(void);
> +int sev_cpu_init(struct svm_cpu_data *sd);
> +extern unsigned int max_sev_asid;
> +#else
> +static inline void sev_free_vcpu(struct kvm_vcpu *vcpu) {}
> +static inline void sev_vm_destroy(struct kvm *kvm) {}
> +static inline void __init sev_set_cpu_caps(void) {}
> +static inline void __init sev_hardware_setup(void) {}
> +static inline void sev_hardware_unsetup(void) {}
> +static inline int sev_cpu_init(struct svm_cpu_data *sd) { return 0; }
> +#define max_sev_asid 0
> +#endif
>  
>  /* vmenter.S */
>  
> -- 

This causes compile errors with -Werror=implicit-function-declaration when
CONFIG_KVM_AMD=y and CONFIG_KVM_AMD_SEV=n.  As discussed in [1], the stubs
aren't needed due to dead code elimination, but the declarations are needed.
[1] https://lore.kernel.org/kvm/ZdjCpX4LMCCyYev9@xxxxxxxxxx/

Please feel free to squash the fix.


  CC      arch/x86/kvm/svm/svm.o
/linux/arch/x86/kvm/svm/svm.c: In function 'init_vmcb':
/linux/arch/x86/kvm/svm/svm.c:1367:17: error: implicit declaration of function 'sev_init_vmcb'; did you mean 'init_vmcb'? [-Werror=implicit-function-declaration]
 1367 |                 sev_init_vmcb(svm);
      |                 ^~~~~~~~~~~~~
      |                 init_vmcb

Similar warnings for sev_es_vcpu_reset(), sev_es_unmap_ghcb(),
sev_es_prepare_switch_to_guest(), sev_es_string_io(), pre_sev_run(),
sev_vcpu_after_set_cpuid(), and sev_vcpu_deliver_sipi_vector().

Reported-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>

---
 arch/x86/kvm/svm/svm.h | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 52bc955ed06f..eff9f19e5bcc 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -663,6 +663,14 @@ void avic_refresh_virtual_apic_mode(struct kvm_vcpu *vcpu);
 
 
 /* sev.c */
+void pre_sev_run(struct vcpu_svm *svm, int cpu);
+void sev_init_vmcb(struct vcpu_svm *svm);
+void sev_vcpu_after_set_cpuid(struct vcpu_svm *svm);
+int sev_es_string_io(struct vcpu_svm *svm, int size, unsigned int port, int in);
+void sev_es_vcpu_reset(struct vcpu_svm *svm);
+void sev_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector);
+void sev_es_prepare_switch_to_guest(struct sev_es_save_area *hostsa);
+void sev_es_unmap_ghcb(struct vcpu_svm *svm);
 
 #ifdef CONFIG_KVM_AMD_SEV
 #define GHCB_VERSION_MAX	1ULL
@@ -677,15 +685,7 @@ int sev_vm_copy_enc_context_from(struct kvm *kvm, unsigned int source_fd);
 int sev_vm_move_enc_context_from(struct kvm *kvm, unsigned int source_fd);
 void sev_guest_memory_reclaimed(struct kvm *kvm);
 
-void pre_sev_run(struct vcpu_svm *svm, int cpu);
-void sev_init_vmcb(struct vcpu_svm *svm);
-void sev_vcpu_after_set_cpuid(struct vcpu_svm *svm);
 int sev_handle_vmgexit(struct kvm_vcpu *vcpu);
-int sev_es_string_io(struct vcpu_svm *svm, int size, unsigned int port, int in);
-void sev_es_vcpu_reset(struct vcpu_svm *svm);
-void sev_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector);
-void sev_es_prepare_switch_to_guest(struct sev_es_save_area *hostsa);
-void sev_es_unmap_ghcb(struct vcpu_svm *svm);
 void sev_free_vcpu(struct kvm_vcpu *vcpu);
 void sev_vm_destroy(struct kvm *kvm);
 void __init sev_set_cpu_caps(void);
-- 
2.43.2

-- 
Isaku Yamahata <isaku.yamahata@xxxxxxxxx>