linux-kernel - [PATCH 06/16] x86/reboot: KVM: Disable SVM during reboot via virt/KVM reboot callback

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Message-ID: <20221201232655.290720-7-seanjc@google.com>
Date:   Thu,  1 Dec 2022 23:26:45 +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 06/16] x86/reboot: KVM: Disable SVM during reboot via virt/KVM
 reboot callback

Use the virt callback to disable SVM (and set GIF=1) during an emergency
instead of blindly attempting to disable SVM.  Like the VMX case, if KVM
(or an out-of-tree hypervisor) isn't loaded/active, SVM can't be in use.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/include/asm/reboot.h  |  2 +-
 arch/x86/include/asm/virtext.h |  8 --------
 arch/x86/kernel/reboot.c       |  6 ++----
 arch/x86/kvm/svm/svm.c         | 19 +++++++++++++++++--
 4 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/arch/x86/include/asm/reboot.h b/arch/x86/include/asm/reboot.h
index 1d098a7d329a..dc2b77e6704b 100644
--- a/arch/x86/include/asm/reboot.h
+++ b/arch/x86/include/asm/reboot.h
@@ -25,7 +25,7 @@ void __noreturn machine_real_restart(unsigned int type);
 #define MRR_BIOS	0
 #define MRR_APM		1
 
-#if IS_ENABLED(CONFIG_KVM_INTEL)
+#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);
diff --git a/arch/x86/include/asm/virtext.h b/arch/x86/include/asm/virtext.h
index 4f61283b1f52..97349410c937 100644
--- a/arch/x86/include/asm/virtext.h
+++ b/arch/x86/include/asm/virtext.h
@@ -130,12 +130,4 @@ static inline void cpu_svm_disable(void)
 	}
 }
 
-/** Makes sure SVM is disabled, if it is supported on the CPU
- */
-static inline void cpu_emergency_svm_disable(void)
-{
-	if (cpu_has_svm(NULL))
-		cpu_svm_disable();
-}
-
 #endif /* _ASM_X86_VIRTEX_H */
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 85ea1fdebf4c..3eec3cdbc054 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -787,7 +787,7 @@ void machine_crash_shutdown(struct pt_regs *regs)
 }
 #endif
 
-#if IS_ENABLED(CONFIG_KVM_INTEL)
+#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;
 
@@ -823,7 +823,7 @@ void cpu_emergency_disable_virtualization(void)
 {
 	lockdep_assert_irqs_disabled();
 
-#if IS_ENABLED(CONFIG_KVM_INTEL)
+#if IS_ENABLED(CONFIG_KVM_INTEL) || IS_ENABLED(CONFIG_KVM_AMD)
 	cpu_emergency_virt_cb *callback;
 
 	rcu_read_lock();
@@ -832,8 +832,6 @@ void cpu_emergency_disable_virtualization(void)
 		callback();
 	rcu_read_unlock();
 #endif
-	/* KVM_AMD doesn't yet utilize the common callback. */
-	cpu_emergency_svm_disable();
 }
 
 #if defined(CONFIG_SMP)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 46b658d0f46e..d56d5fe42262 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -38,6 +38,7 @@
 #include <asm/spec-ctrl.h>
 #include <asm/cpu_device_id.h>
 #include <asm/traps.h>
+#include <asm/reboot.h>
 #include <asm/fpu/api.h>
 
 #include <asm/virtext.h>
@@ -565,6 +566,11 @@ void __svm_write_tsc_multiplier(u64 multiplier)
 	preempt_enable();
 }
 
+static void svm_emergency_disable(void)
+{
+	cpu_svm_disable();
+}
+
 static void svm_hardware_disable(void)
 {
 	/* Make sure we clean up behind us */
@@ -5084,6 +5090,13 @@ static struct kvm_x86_init_ops svm_init_ops __initdata = {
 	.pmu_ops = &amd_pmu_ops,
 };
 
+static void __svm_exit(void)
+{
+	kvm_x86_vendor_exit();
+
+	cpu_emergency_unregister_virt_callback(svm_emergency_disable);
+}
+
 static int __init svm_init(void)
 {
 	int r;
@@ -5097,6 +5110,8 @@ static int __init svm_init(void)
 	if (r)
 		return r;
 
+	cpu_emergency_register_virt_callback(svm_emergency_disable);
+
 	/*
 	 * Common KVM initialization _must_ come last, after this, /dev/kvm is
 	 * exposed to userspace!
@@ -5109,14 +5124,14 @@ static int __init svm_init(void)
 	return 0;
 
 err_kvm_init:
-	kvm_x86_vendor_exit();
+	__svm_exit();
 	return r;
 }
 
 static void __exit svm_exit(void)
 {
 	kvm_exit();
-	kvm_x86_vendor_exit();
+	__svm_exit();
 }
 
 module_init(svm_init)
-- 
2.39.0.rc0.267.gcb52ba06e7-goog