Messages in this thread Patch in this message | | | From | Paolo Bonzini <> | Subject | [PATCH v3 5/7] KVM: x86: never write to memory from kvm_vcpu_check_block | Date | Mon, 22 Aug 2022 13:06:57 -0400 |
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kvm_vcpu_check_block() is called while not in TASK_RUNNING, and therefore it cannot sleep. Writing to guest memory is therefore forbidden, but it can happen on AMD processors if kvm_check_nested_events() causes a vmexit.
Fortunately, all events that are caught by kvm_check_nested_events() are also recognized by kvm_vcpu_has_events() through vendor callbacks such as kvm_x86_interrupt_allowed() or kvm_x86_ops.nested_ops->has_events(), so remove the call and postpone the actual processing to vcpu_block().
Reported-by: Maxim Levitsky <mlevitsk@redhat.com> Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- arch/x86/kvm/x86.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 5c5341110876..f901cd872b6d 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -10637,6 +10637,15 @@ static inline int vcpu_block(struct kvm_vcpu *vcpu) return 1; } + /* + * Evaluate nested events before exiting the halted state. This allows + * the halt state to be recorded properly in the VMCS12's activity + * state field (AMD does not have a similar field and a VM-Exit always + * causes a spurious wakeup from HLT). + */ + if (is_guest_mode(vcpu)) + kvm_check_nested_events(vcpu); + if (kvm_apic_accept_events(vcpu) < 0) return 0; switch(vcpu->arch.mp_state) { @@ -10660,9 +10669,6 @@ static inline int vcpu_block(struct kvm_vcpu *vcpu) static inline bool kvm_vcpu_running(struct kvm_vcpu *vcpu) { - if (is_guest_mode(vcpu)) - kvm_check_nested_events(vcpu); - return (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE && !vcpu->arch.apf.halted); } -- 2.31.1
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