From 4059172b2a78a71d15d8fcd8d3fd8ea1ba65d25b Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Fri, 13 Feb 2026 17:26:47 -0800 Subject: [PATCH] KVM: x86: Move kvm_rebooting to x86 Move kvm_rebooting, which is only read by x86, to KVM x86 so that it can be moved again to core x86 code. Add a "shutdown" arch hook to facilate setting the flag in KVM x86, along with a pile of comments to provide more context around what KVM x86 is doing and why. Reviewed-by: Chao Gao Acked-by: Dave Hansen Tested-by: Chao Gao Reviewed-by: Dan Williams Tested-by: Sagi Shahar Link: https://patch.msgid.link/20260214012702.2368778-2-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 22 ++++++++++++++++++++++ arch/x86/kvm/x86.h | 1 + include/linux/kvm_host.h | 8 +++++++- virt/kvm/kvm_main.c | 14 +++++++------- 4 files changed, 37 insertions(+), 8 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a035307957077..7ac3578e6ec00 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -700,6 +700,9 @@ static void drop_user_return_notifiers(void) kvm_on_user_return(&msrs->urn); } +__visible bool kvm_rebooting; +EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_rebooting); + /* * Handle a fault on a hardware virtualization (VMX or SVM) instruction. * @@ -13177,6 +13180,25 @@ int kvm_arch_enable_virtualization_cpu(void) return 0; } +void kvm_arch_shutdown(void) +{ + /* + * Set kvm_rebooting to indicate that KVM has asynchronously disabled + * hardware virtualization, i.e. that errors and/or exceptions on SVM + * and VMX instructions are expected and should be ignored. + */ + kvm_rebooting = true; + + /* + * Ensure kvm_rebooting is visible before IPIs are sent to other CPUs + * to disable virtualization. Effectively pairs with the reception of + * the IPI (kvm_rebooting is read in task/exception context, but only + * _needs_ to be read as %true after the IPI function callback disables + * virtualization). + */ + smp_wmb(); +} + void kvm_arch_disable_virtualization_cpu(void) { kvm_x86_call(disable_virtualization_cpu)(); diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h index 94d4f07aaaa09..b314649e5c025 100644 --- a/arch/x86/kvm/x86.h +++ b/arch/x86/kvm/x86.h @@ -54,6 +54,7 @@ struct kvm_host_values { u64 arch_capabilities; }; +extern bool kvm_rebooting; void kvm_spurious_fault(void); #define SIZE_OF_MEMSLOTS_HASHTABLE \ diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 34759a262b289..7c4ebd5210ecc 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1627,6 +1627,13 @@ static inline void kvm_create_vcpu_debugfs(struct kvm_vcpu *vcpu) {} #endif #ifdef CONFIG_KVM_GENERIC_HARDWARE_ENABLING +/* + * kvm_arch_shutdown() is invoked immediately prior to forcefully disabling + * hardware virtualization on all CPUs via IPI function calls (in preparation + * for shutdown or reboot), e.g. to allow arch code to prepare for disabling + * virtualization while KVM may be actively running vCPUs. + */ +void kvm_arch_shutdown(void); /* * kvm_arch_{enable,disable}_virtualization() are called on one CPU, under * kvm_usage_lock, immediately after/before 0=>1 and 1=>0 transitions of @@ -2313,7 +2320,6 @@ static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu) #ifdef CONFIG_KVM_GENERIC_HARDWARE_ENABLING extern bool enable_virt_at_load; -extern bool kvm_rebooting; #endif extern unsigned int halt_poll_ns; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 1bc1da66b4b02..d27bf2488b125 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -5578,13 +5578,15 @@ bool enable_virt_at_load = true; module_param(enable_virt_at_load, bool, 0444); EXPORT_SYMBOL_FOR_KVM_INTERNAL(enable_virt_at_load); -__visible bool kvm_rebooting; -EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_rebooting); - static DEFINE_PER_CPU(bool, virtualization_enabled); static DEFINE_MUTEX(kvm_usage_lock); static int kvm_usage_count; +__weak void kvm_arch_shutdown(void) +{ + +} + __weak void kvm_arch_enable_virtualization(void) { @@ -5638,10 +5640,9 @@ static int kvm_offline_cpu(unsigned int cpu) static void kvm_shutdown(void *data) { + kvm_arch_shutdown(); + /* - * Disable hardware virtualization and set kvm_rebooting to indicate - * that KVM has asynchronously disabled hardware virtualization, i.e. - * that relevant errors and exceptions aren't entirely unexpected. * Some flavors of hardware virtualization need to be disabled before * transferring control to firmware (to perform shutdown/reboot), e.g. * on x86, virtualization can block INIT interrupts, which are used by @@ -5650,7 +5651,6 @@ static void kvm_shutdown(void *data) * 100% comprehensive. */ pr_info("kvm: exiting hardware virtualization\n"); - kvm_rebooting = true; on_each_cpu(kvm_disable_virtualization_cpu, NULL, 1); } -- 2.47.3