diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index 49b1154366ce..888526ce4dab 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -206,13 +206,19 @@ static struct kvm_vcpu *get_vcpu_by_vpidx(struct kvm *kvm, u32 vpidx) static struct kvm_vcpu_hv_synic *synic_get(struct kvm *kvm, u32 vpidx) { - struct kvm_vcpu *vcpu; struct kvm_vcpu_hv_synic *synic; + struct kvm_vcpu_hv *hv_vcpu; + struct kvm_vcpu *vcpu; vcpu = get_vcpu_by_vpidx(kvm, vpidx); - if (!vcpu || !to_hv_vcpu(vcpu)) + if (!vcpu) return NULL; - synic = to_hv_synic(vcpu); + + hv_vcpu = to_hv_vcpu_safe(vcpu); + if (!hv_vcpu) + return NULL; + + synic = &hv_vcpu->synic; return (synic->active) ? synic : NULL; } @@ -972,7 +978,6 @@ int kvm_hv_vcpu_init(struct kvm_vcpu *vcpu) if (!hv_vcpu) return -ENOMEM; - vcpu->arch.hyperv = hv_vcpu; hv_vcpu->vcpu = vcpu; synic_init(&hv_vcpu->synic); @@ -988,6 +993,14 @@ int kvm_hv_vcpu_init(struct kvm_vcpu *vcpu) spin_lock_init(&hv_vcpu->tlb_flush_fifo[i].write_lock); } + /* + * Ensure the structure is fully initialized before it's visible to + * other tasks, as much of the state can be legally accessed without + * holding vcpu->mutex. + * + * Pairs with the smp_load_acquire() in to_hv_vcpu_safe(). + */ + smp_store_release(&vcpu->arch.hyperv, hv_vcpu); return 0; } @@ -2165,7 +2178,7 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc) bitmap_zero(vcpu_mask, KVM_MAX_VCPUS); kvm_for_each_vcpu(i, v, kvm) { - hv_v = to_hv_vcpu(v); + hv_v = to_hv_vcpu_safe(v); /* * The following check races with nested vCPUs entering/exiting diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h index 2da11b967c41..ea9c81d76dd3 100644 --- a/arch/x86/kvm/hyperv.h +++ b/arch/x86/kvm/hyperv.h @@ -62,6 +62,18 @@ static inline struct kvm_hv *to_kvm_hv(struct kvm *kvm) return &kvm->arch.hyperv; } +static inline struct kvm_vcpu_hv *to_hv_vcpu_safe(struct kvm_vcpu *vcpu) +{ + /* + * Ensure the HyperV structure is fully initialized when accessing it + * without holding vcpu->mutex (or some other guarantee that KVM can't + * concurrently instantiate the structure). + * + * Pairs with the smp_store_release() in kvm_hv_vcpu_init(). + */ + return smp_load_acquire(&vcpu->arch.hyperv); +} + static inline struct kvm_vcpu_hv *to_hv_vcpu(struct kvm_vcpu *vcpu) { return vcpu->arch.hyperv; @@ -88,7 +100,7 @@ static inline struct kvm_hv_syndbg *to_hv_syndbg(struct kvm_vcpu *vcpu) static inline u32 kvm_hv_get_vpindex(struct kvm_vcpu *vcpu) { - struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu); + struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu_safe(vcpu); return hv_vcpu ? hv_vcpu->vp_index : vcpu->vcpu_idx; } @@ -142,7 +154,7 @@ static inline struct kvm_vcpu *hv_stimer_to_vcpu(struct kvm_vcpu_hv_stimer *stim static inline bool kvm_hv_has_stimer_pending(struct kvm_vcpu *vcpu) { - struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu); + struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu_safe(vcpu); if (!hv_vcpu) return false; @@ -198,7 +210,7 @@ int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid, static inline struct kvm_vcpu_hv_tlb_flush_fifo *kvm_hv_get_tlb_flush_fifo(struct kvm_vcpu *vcpu, bool is_guest_mode) { - struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu); + struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu_safe(vcpu); int i = is_guest_mode ? HV_L2_TLB_FLUSH_FIFO : HV_L1_TLB_FLUSH_FIFO;