linux-kernel - [PATCH v2 02/18] x86/reboot: Expose VMCS crash hooks if and only if KVM

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Message-ID: <20230310214232.806108-3-seanjc@google.com>
Date:   Fri, 10 Mar 2023 13:42:16 -0800
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:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Andrew Cooper <Andrew.Cooper3@...rix.com>,
        Kai Huang <kai.huang@...el.com>, Chao Gao <chao.gao@...el.com>
Subject: [PATCH v2 02/18] x86/reboot: Expose VMCS crash hooks if and only if
 KVM_INTEL is enabled

Expose the crash/reboot hooks used by KVM to do VMCLEAR+VMXOFF if and
only if there's a potential in-tree user, KVM_INTEL.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/include/asm/reboot.h | 2 ++
 arch/x86/kernel/reboot.c      | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/arch/x86/include/asm/reboot.h b/arch/x86/include/asm/reboot.h
index 2551baec927d..33c8e911e0de 100644
--- a/arch/x86/include/asm/reboot.h
+++ b/arch/x86/include/asm/reboot.h
@@ -25,8 +25,10 @@ void __noreturn machine_real_restart(unsigned int type);
 #define MRR_BIOS	0
 #define MRR_APM		1
 
+#if IS_ENABLED(CONFIG_KVM_INTEL)
 typedef void crash_vmclear_fn(void);
 extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss;
+#endif
 void cpu_emergency_disable_virtualization(void);
 
 typedef void (*nmi_shootdown_cb)(int, struct pt_regs*);
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 299b970e5f82..6c0b1634b884 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -787,6 +787,7 @@ void machine_crash_shutdown(struct pt_regs *regs)
 }
 #endif
 
+#if IS_ENABLED(CONFIG_KVM_INTEL)
 /*
  * This is used to VMCLEAR all VMCSs loaded on the
  * processor. And when loading kvm_intel module, the
@@ -807,6 +808,7 @@ static inline void cpu_crash_vmclear_loaded_vmcss(void)
 		do_vmclear_operation();
 	rcu_read_unlock();
 }
+#endif
 
 /* This is the CPU performing the emergency shutdown work. */
 int crashing_cpu = -1;
@@ -818,7 +820,9 @@ int crashing_cpu = -1;
  */
 void cpu_emergency_disable_virtualization(void)
 {
+#if IS_ENABLED(CONFIG_KVM_INTEL)
 	cpu_crash_vmclear_loaded_vmcss();
+#endif
 
 	cpu_emergency_vmxoff();
 	cpu_emergency_svm_disable();
-- 
2.40.0.rc1.284.g88254d51c5-goog