Re: [PATCH v3 RESEND] kvm: vmx: Properly handle machine check during VM-entry

["Radim Krčmář" <rkrcmar@redhat.com>]

2017-06-29 13:01-0700, Jim Mattson:
> vmx_complete_atomic_exit should call kvm_machine_check for any
> VM-entry failure due to a machine-check event. Such an exit should be
> recognized solely by its basic exit reason (i.e. the low 16 bits of
> the VMCS exit reason field). None of the other VMCS exit information
> fields contain valid information when the VM-exit is due to "VM-entry
> failure due to machine-check event".
> 
> Signed-off-by: Jim Mattson <jmattson@google.com>
> ---
>  arch/x86/kvm/vmx.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index ca5d2b93385c..42db3eb2d13b 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -8591,17 +8591,20 @@ static void vmx_apicv_post_state_restore(struct kvm_vcpu *vcpu)
>  
>  static void vmx_complete_atomic_exit(struct vcpu_vmx *vmx)
>  {
> -	u32 exit_intr_info;
> +	u32 exit_intr_info = 0;
> +	u16 basic_exit_reason = (u16)vmx->exit_reason;
>  
> -	if (!(vmx->exit_reason == EXIT_REASON_MCE_DURING_VMENTRY
> -	      || vmx->exit_reason == EXIT_REASON_EXCEPTION_NMI))
> +	if (!(basic_exit_reason == EXIT_REASON_MCE_DURING_VMENTRY
> +	      || basic_exit_reason == EXIT_REASON_EXCEPTION_NMI))
>  		return;
>  
> -	vmx->exit_intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
> -	exit_intr_info = vmx->exit_intr_info;
> +	if (basic_exit_reason != EXIT_REASON_MCE_DURING_VMENTRY)

I think this would be clearer as

  if (!(vmx->exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY))

because that is the actual reason why VM_EXIT_INTR_INFO is not useable.
I'm ok with the original too, and will change that while applying if you
agree,

thanks.

> +		exit_intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
> +	vmx->exit_intr_info = exit_intr_info;
>  
>  	/* Handle machine checks before interrupts are enabled */
> -	if (is_machine_check(exit_intr_info))
> +	if (basic_exit_reason == EXIT_REASON_MCE_DURING_VMENTRY ||
> +	    is_machine_check(exit_intr_info))
>  		kvm_machine_check();
>  
>  	/* We need to handle NMIs before interrupts are enabled */
> -- 
> 2.13.2.725.g09c95d1e9-goog
>