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

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Date:   Thu,  5 Oct 2023 16:13:57 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.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
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Elena Reshetova <elena.reshetova@...el.com>,
        Jun Nakajima <jun.nakajima@...el.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        kexec@...ts.infradead.org, linux-coco@...ts.linux.dev,
        linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH 08/13] KVM: x86: Add config option to gate emergency virt callback support

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@...ux.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