[PATCH v3 08/18] x86/reboot: Expose VMCS crash hooks if and only if KVM_{INTEL,AMD} is enabled

Sean Christopherson
2023-05-12T23:51:35Z

Expose the crash/reboot hooks used by KVM to disable virtualization in
hardware and unblock INIT only if there's a potential in-tree user,
i.e. either KVM_INTEL or KVM_AMD is enabled.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/include/asm/reboot.h | 4 ++++
arch/x86/kernel/reboot.c | 5 ++++-
2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/reboot.h b/arch/x86/include/asm/reboot.h
index d9a38d379d18..9cf0b21bf495 100644
--- a/arch/x86/include/asm/reboot.h
+++ b/arch/x86/include/asm/reboot.h
@@ -25,10 +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)
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 */

typedef void (*nmi_shootdown_cb)(int, struct pt_regs*);
void nmi_panic_self_stop(struct pt_regs *regs);
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 493d66e59a4f..6818d8de85a1 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -529,6 +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)
/* RCU-protected callback to disable virtualization prior to reboot. */
static cpu_emergency_virt_cb __rcu *cpu_emergency_virt_callback;

@@ -596,7 +597,9 @@ static void emergency_reboot_disable_virtualization(void)
nmi_shootdown_cpus_on_restart();
}
}
-
+#else
+static void emergency_reboot_disable_virtualization(void) { }
+#endif /* CONFIG_KVM_INTEL || CONFIG_KVM_AMD */

void __attribute__((weak)) mach_reboot_fixups(void)
{
--
2.40.1.606.ga4b1b128d6-goog