From 119b5cb4ffd0166f3e98e9ee042f5046f7744f28 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Fri, 21 Jul 2023 13:18:43 -0700 Subject: [PATCH] x86/reboot: KVM: Handle VMXOFF in KVM's reboot callback Use KVM VMX's reboot/crash callback to do VMXOFF in an emergency instead of manually and blindly doing VMXOFF. There's no need to attempt VMXOFF if a hypervisor, i.e. KVM, isn't loaded/active, i.e. if the CPU can't possibly be post-VMXON. Reviewed-by: Kai Huang Link: https://lore.kernel.org/r/20230721201859.2307736-4-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/include/asm/virtext.h | 10 ---------- arch/x86/kernel/reboot.c | 29 +++++++++-------------------- arch/x86/kvm/vmx/vmx.c | 8 +++++--- 3 files changed, 14 insertions(+), 33 deletions(-) diff --git a/arch/x86/include/asm/virtext.h b/arch/x86/include/asm/virtext.h index 3b12e6b994123..5bc29fab15da7 100644 --- a/arch/x86/include/asm/virtext.h +++ b/arch/x86/include/asm/virtext.h @@ -70,16 +70,6 @@ static inline void __cpu_emergency_vmxoff(void) cpu_vmxoff(); } -/** Disable VMX if it is supported and enabled on the current CPU - */ -static inline void cpu_emergency_vmxoff(void) -{ - if (cpu_has_vmx()) - __cpu_emergency_vmxoff(); -} - - - /* * SVM functions: diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c index 62ccedeb5e2b8..d2d0f2672a64d 100644 --- a/arch/x86/kernel/reboot.c +++ b/arch/x86/kernel/reboot.c @@ -787,13 +787,7 @@ void machine_crash_shutdown(struct pt_regs *regs) } #endif -/* - * This is used to VMCLEAR all VMCSs loaded on the - * processor. And when loading kvm_intel module, the - * callback function pointer will be assigned. - * - * protected by rcu. - */ +/* 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) @@ -815,17 +809,6 @@ void cpu_emergency_unregister_virt_callback(cpu_emergency_virt_cb *callback) } EXPORT_SYMBOL_GPL(cpu_emergency_unregister_virt_callback); -static inline void cpu_crash_vmclear_loaded_vmcss(void) -{ - cpu_emergency_virt_cb *callback; - - rcu_read_lock(); - callback = rcu_dereference(cpu_emergency_virt_callback); - if (callback) - callback(); - rcu_read_unlock(); -} - /* This is the CPU performing the emergency shutdown work. */ int crashing_cpu = -1; @@ -836,9 +819,15 @@ int crashing_cpu = -1; */ void cpu_emergency_disable_virtualization(void) { - cpu_crash_vmclear_loaded_vmcss(); + cpu_emergency_virt_cb *callback; + + rcu_read_lock(); + callback = rcu_dereference(cpu_emergency_virt_callback); + if (callback) + callback(); + rcu_read_unlock(); - cpu_emergency_vmxoff(); + /* KVM_AMD doesn't yet utilize the common callback. */ cpu_emergency_svm_disable(); } diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 661ba09685b8a..df991f15baf49 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -725,7 +725,7 @@ static int vmx_set_guest_uret_msr(struct vcpu_vmx *vmx, return ret; } -static void crash_vmclear_local_loaded_vmcss(void) +static void vmx_emergency_disable(void) { int cpu = raw_smp_processor_id(); struct loaded_vmcs *v; @@ -733,6 +733,8 @@ static void crash_vmclear_local_loaded_vmcss(void) list_for_each_entry(v, &per_cpu(loaded_vmcss_on_cpu, cpu), loaded_vmcss_on_cpu_link) vmcs_clear(v->vmcs); + + __cpu_emergency_vmxoff(); } static void __loaded_vmcs_clear(void *arg) @@ -8571,7 +8573,7 @@ static void __vmx_exit(void) { allow_smaller_maxphyaddr = false; - cpu_emergency_unregister_virt_callback(crash_vmclear_local_loaded_vmcss); + cpu_emergency_unregister_virt_callback(vmx_emergency_disable); vmx_cleanup_l1d_flush(); } @@ -8619,7 +8621,7 @@ static int __init vmx_init(void) pi_init_cpu(cpu); } - cpu_emergency_register_virt_callback(crash_vmclear_local_loaded_vmcss); + cpu_emergency_register_virt_callback(vmx_emergency_disable); vmx_check_vmcs12_offsets(); -- 2.30.2