From 3f749befb0998472470d850b11b430477c0718cc Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 29 Sep 2024 14:47:33 -0700 Subject: [PATCH] x86: kvm: fix build error MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The cpu_emergency_register_virt_callback() function is used unconditionally by the x86 kvm code, but it is declared (and defined) conditionally: #if IS_ENABLED(CONFIG_KVM_INTEL) || IS_ENABLED(CONFIG_KVM_AMD) void cpu_emergency_register_virt_callback(cpu_emergency_virt_cb *callback); ... leading to a build error when neither KVM_INTEL nor KVM_AMD support is enabled: arch/x86/kvm/x86.c: In function ‘kvm_arch_enable_virtualization’: arch/x86/kvm/x86.c:12517:9: error: implicit declaration of function ‘cpu_emergency_register_virt_callback’ [-Wimplicit-function-declaration] 12517 | cpu_emergency_register_virt_callback(kvm_x86_ops.emergency_disable_virtualization_cpu); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/x86/kvm/x86.c: In function ‘kvm_arch_disable_virtualization’: arch/x86/kvm/x86.c:12522:9: error: implicit declaration of function ‘cpu_emergency_unregister_virt_callback’ [-Wimplicit-function-declaration] 12522 | cpu_emergency_unregister_virt_callback(kvm_x86_ops.emergency_disable_virtualization_cpu); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Fix the build by defining empty helper functions the same way the old cpu_emergency_disable_virtualization() function was dealt with for the same situation. Maybe we could instead have made the call sites conditional, since the callers (kvm_arch_{en,dis}able_virtualization()) have an empty weak fallback. I'll leave that to the kvm people to argue about, this at least gets the build going for that particular config. Fixes: 590b09b1d88e ("KVM: x86: Register "emergency disable" callbacks when virt is enabled") Cc: Paolo Bonzini Cc: Sean Christopherson Cc: Kai Huang Cc: Chao Gao Cc: Farrah Chen Signed-off-by: Linus Torvalds --- arch/x86/include/asm/reboot.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/include/asm/reboot.h b/arch/x86/include/asm/reboot.h index d0ef2a678d66..c02183d3cdd7 100644 --- a/arch/x86/include/asm/reboot.h +++ b/arch/x86/include/asm/reboot.h @@ -31,6 +31,8 @@ void cpu_emergency_register_virt_callback(cpu_emergency_virt_cb *callback); void cpu_emergency_unregister_virt_callback(cpu_emergency_virt_cb *callback); void cpu_emergency_disable_virtualization(void); #else +static inline void cpu_emergency_register_virt_callback(cpu_emergency_virt_cb *callback) {} +static inline void cpu_emergency_unregister_virt_callback(cpu_emergency_virt_cb *callback) {} static inline void cpu_emergency_disable_virtualization(void) {} #endif /* CONFIG_KVM_INTEL || CONFIG_KVM_AMD */