linux-kernel - [PATCH 07/16] x86/reboot: Hoist "disable virt" helpers above "emergency reboot" path

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Date:   Thu,  1 Dec 2022 23:26:46 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, Andrew Cooper <Andrew.Cooper3@...rix.com>
Subject: [PATCH 07/16] x86/reboot: Hoist "disable virt" helpers above
 "emergency reboot" path

Move the various "disable virtualization" helpers above the emergency
reboot path so that emergency_reboot_disable_virtualization() can be
stubbed out in a future patch if neither KVM_INTEL nor KVM_AMD is enabled,
i.e. if there is no in-tree user of CPU virtualization.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/include/asm/reboot.h |  4 +-
 arch/x86/kernel/reboot.c      | 86 +++++++++++++++++------------------
 2 files changed, 45 insertions(+), 45 deletions(-)

diff --git a/arch/x86/include/asm/reboot.h b/arch/x86/include/asm/reboot.h
index dc2b77e6704b..2be5b89c9a05 100644
--- a/arch/x86/include/asm/reboot.h
+++ b/arch/x86/include/asm/reboot.h
@@ -29,8 +29,10 @@ void __noreturn machine_real_restart(unsigned int type);
 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);
-#endif
 void cpu_emergency_disable_virtualization(void);
+#else
+static inline void cpu_emergency_disable_virtualization(void) {}
+#endif
 
 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 3eec3cdbc054..a006ddaa1405 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -530,6 +530,48 @@ 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;
+
+void cpu_emergency_register_virt_callback(cpu_emergency_virt_cb *callback)
+{
+	if (WARN_ON_ONCE(rcu_access_pointer(cpu_emergency_virt_callback)))
+		return;
+
+	rcu_assign_pointer(cpu_emergency_virt_callback, callback);
+}
+EXPORT_SYMBOL_GPL(cpu_emergency_register_virt_callback);
+
+void cpu_emergency_unregister_virt_callback(cpu_emergency_virt_cb *callback)
+{
+	if (WARN_ON_ONCE(rcu_access_pointer(cpu_emergency_virt_callback) != callback))
+		return;
+
+	rcu_assign_pointer(cpu_emergency_virt_callback, NULL);
+	synchronize_rcu();
+}
+EXPORT_SYMBOL_GPL(cpu_emergency_unregister_virt_callback);
+
+/*
+ * Disable virtualization, i.e. VMX or SVM, to ensure INIT is recognized during
+ * reboot.  VMX blocks INIT if the CPU is post-VMXON, and SVM blocks INIT if
+ * GIF=0, i.e. if the crash occurred between CLGI and STGI.
+ */
+void cpu_emergency_disable_virtualization(void)
+{
+	cpu_emergency_virt_cb *callback;
+
+	lockdep_assert_irqs_disabled();
+
+	rcu_read_lock();
+	callback = rcu_dereference(cpu_emergency_virt_callback);
+	if (callback)
+		callback();
+	rcu_read_unlock();
+}
+#endif /* CONFIG_KVM_INTEL || CONFIG_KVM_AMD */
+
 static void emergency_reboot_disable_virtualization(void)
 {
 	/* Just make sure we won't change CPUs while doing this */
@@ -787,53 +829,9 @@ void machine_crash_shutdown(struct pt_regs *regs)
 }
 #endif
 
-#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;
-
-void cpu_emergency_register_virt_callback(cpu_emergency_virt_cb *callback)
-{
-	if (WARN_ON_ONCE(rcu_access_pointer(cpu_emergency_virt_callback)))
-		return;
-
-	rcu_assign_pointer(cpu_emergency_virt_callback, callback);
-}
-EXPORT_SYMBOL_GPL(cpu_emergency_register_virt_callback);
-
-void cpu_emergency_unregister_virt_callback(cpu_emergency_virt_cb *callback)
-{
-	if (WARN_ON_ONCE(rcu_access_pointer(cpu_emergency_virt_callback) != callback))
-		return;
-
-	rcu_assign_pointer(cpu_emergency_virt_callback, NULL);
-	synchronize_rcu();
-}
-EXPORT_SYMBOL_GPL(cpu_emergency_unregister_virt_callback);
-#endif
-
 /* This is the CPU performing the emergency shutdown work. */
 int crashing_cpu = -1;
 
-/*
- * Disable virtualization, i.e. VMX or SVM, to ensure INIT is recognized during
- * reboot.  VMX blocks INIT if the CPU is post-VMXON, and SVM blocks INIT if
- * GIF=0, i.e. if the crash occurred between CLGI and STGI.
- */
-void cpu_emergency_disable_virtualization(void)
-{
-	lockdep_assert_irqs_disabled();
-
-#if IS_ENABLED(CONFIG_KVM_INTEL) || IS_ENABLED(CONFIG_KVM_AMD)
-	cpu_emergency_virt_cb *callback;
-
-	rcu_read_lock();
-	callback = rcu_dereference(cpu_emergency_virt_callback);
-	if (callback)
-		callback();
-	rcu_read_unlock();
-#endif
-}
-
 #if defined(CONFIG_SMP)
 
 static nmi_shootdown_cb shootdown_callback;
-- 
2.39.0.rc0.267.gcb52ba06e7-goog