[PATCH 08/13] KVM: x86: Add config option to gate emergency virt callback support

["Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>]

KVM uses emergency virt call back to shutdown virtualization extension
during crash, so the crash kernel can work correctly.

So far the virt callback is only supported if KVM_INTEL or KVM_AMD is
enabled. TDX guest has similar needs.

Add a config option to gate virt emergency callback support.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/include/asm/reboot.h | 4 ++--
 arch/x86/kernel/reboot.c      | 4 ++--
 arch/x86/kvm/Kconfig          | 5 +++++
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/reboot.h b/arch/x86/include/asm/reboot.h
index 6536873f8fc0..f72bdd4abbe8 100644
--- a/arch/x86/include/asm/reboot.h
+++ b/arch/x86/include/asm/reboot.h
@@ -25,14 +25,14 @@ void __noreturn machine_real_restart(unsigned int type);
 #define MRR_BIOS	0
 #define MRR_APM		1
 
-#if IS_ENABLED(CONFIG_KVM_INTEL) || IS_ENABLED(CONFIG_KVM_AMD)
+#ifdef CONFIG_EMERGENCY_VIRT_CALLBACK
 typedef void (cpu_emergency_virt_cb)(void);
 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_disable_virtualization(void) {}
-#endif /* CONFIG_KVM_INTEL || CONFIG_KVM_AMD */
+#endif /* CONFIG_EMERGENCY_VIRT_CALLBACK */
 
 typedef void (*nmi_shootdown_cb)(int, struct pt_regs*);
 void nmi_shootdown_cpus(nmi_shootdown_cb callback);
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 830425e6d38e..6a781f2f11c8 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -529,7 +529,7 @@ static inline void kb_wait(void)
 
 static inline void nmi_shootdown_cpus_on_restart(void);
 
-#if IS_ENABLED(CONFIG_KVM_INTEL) || IS_ENABLED(CONFIG_KVM_AMD)
+#ifdef CONFIG_EMERGENCY_VIRT_CALLBACK
 /* RCU-protected callback to disable virtualization prior to reboot. */
 static cpu_emergency_virt_cb __rcu *cpu_emergency_virt_callback;
 
@@ -599,7 +599,7 @@ static void emergency_reboot_disable_virtualization(void)
 }
 #else
 static void emergency_reboot_disable_virtualization(void) { }
-#endif /* CONFIG_KVM_INTEL || CONFIG_KVM_AMD */
+#endif /* CONFIG_EMERGENCY_VIRT_CALLBACK */
 
 void __attribute__((weak)) mach_reboot_fixups(void)
 {
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index ed90f148140d..7df3f0c45cfe 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -80,6 +80,7 @@ config KVM_WERROR
 config KVM_INTEL
 	tristate "KVM for Intel (and compatible) processors support"
 	depends on KVM && IA32_FEAT_CTL
+	select EMERGENCY_VIRT_CALLBACK
 	help
 	  Provides support for KVM on processors equipped with Intel's VT
 	  extensions, a.k.a. Virtual Machine Extensions (VMX).
@@ -102,6 +103,7 @@ config X86_SGX_KVM
 config KVM_AMD
 	tristate "KVM for AMD processors support"
 	depends on KVM && (CPU_SUP_AMD || CPU_SUP_HYGON)
+	select EMERGENCY_VIRT_CALLBACK
 	help
 	  Provides support for KVM on AMD processors equipped with the AMD-V
 	  (SVM) extensions.
@@ -155,3 +157,6 @@ config KVM_EXTERNAL_WRITE_TRACKING
 	bool
 
 endif # VIRTUALIZATION
+
+config EMERGENCY_VIRT_CALLBACK
+	bool
-- 
2.41.0