On 10/24/2014 08:07 AM, Paolo Bonzini wrote:
> From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
>
> KVM_EXIT_UNKNOWN is a kvm bug, we don't really know whether it was
> triggered by a priveledged application. Let's not kill the guest: WARN
> and inject #UD instead.
This scares me a bit. For guest CPL3, it's probably okay. For guest
CPL0, on the other hand, #UD might not use IST (or a task switch on
32-bit guests), resulting in possible corruption if unprivileged code
controls SP. Admittedly, there aren't that many contexts from which
that should happen (on Linux, at least), but something like #DF (or even
a triple fault) might be safer if the guest is at CPL0 when this happens.
--Andy
>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> arch/x86/kvm/svm.c | 6 +++---
> arch/x86/kvm/vmx.c | 6 +++---
> 2 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 00bed2c5e948..7527cefc5a43 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -3551,9 +3551,9 @@ static int handle_exit(struct kvm_vcpu *vcpu)
>
> if (exit_code >= ARRAY_SIZE(svm_exit_handlers)
> || !svm_exit_handlers[exit_code]) {
> - kvm_run->exit_reason = KVM_EXIT_UNKNOWN;
> - kvm_run->hw.hardware_exit_reason = exit_code;
> - return 0;
> + WARN_ONCE(1, "vmx: unexpected exit reason 0x%x\n", exit_code);
> + kvm_queue_exception(vcpu, UD_VECTOR);
> + return 1;
> }
>
> return svm_exit_handlers[exit_code](svm);
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index cf3cd079ec52..a8b76c4c95e2 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -7174,10 +7174,10 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu)
> && kvm_vmx_exit_handlers[exit_reason])
> return kvm_vmx_exit_handlers[exit_reason](vcpu);
> else {
> - vcpu->run->exit_reason = KVM_EXIT_UNKNOWN;
> - vcpu->run->hw.hardware_exit_reason = exit_reason;
> + WARN_ONCE(1, "vmx: unexpected exit reason 0x%x\n", exit_reason);
> + kvm_queue_exception(vcpu, UD_VECTOR);
> + return 1;
> }
> - return 0;
> }
>
> static void update_cr8_intercept(struct kvm_vcpu *vcpu, int tpr, int irr)
>
--
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