Messages in this thread Patch in this message | | | From | Paolo Bonzini <> | Subject | [PATCH v2 9/9] KVM: x86: never write to memory from kvm_vcpu_check_block | Date | Thu, 11 Aug 2022 17:06:05 -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().
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- arch/x86/kvm/x86.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 5e9358ea112b..9226fd536783 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -10639,6 +10639,17 @@ static inline int vcpu_block(struct kvm_vcpu *vcpu) return 1; } + if (is_guest_mode(vcpu)) { + /* + * 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 vmexit always causes a spurious + * wakeup from HLT). + */ + kvm_check_nested_events(vcpu); + } + if (kvm_apic_accept_events(vcpu) < 0) return 0; switch(vcpu->arch.mp_state) { @@ -10662,9 +10673,6 @@ 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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