Re: [Xen-devel] [PATCH] x86/hvm: Fix the unknown nested vmexit reason 80000021 bug

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 07/04/15 14:27, Liang Li wrote:
> This bug will be trigged when NMI happen in the L2 guest. The current
> code handles the NMI incorrectly. According to Intel SDM 31.7.1.2
> (Resuming Guest Software after Handling an Exception), If bit 31 of the
> IDT-vectoring information fields is set, and the virtual NMIs VM-execution
> control is 1, while bits 10:8 in the IDT-vectoring information field is
> 2, bit 3 in the interruptibility-state field should be cleared to avoid
> the next VM entry fail.
>
> Signed-off-by: Liang Li <liang.z.li@xxxxxxxxx>
> ---
>  xen/arch/x86/hvm/vmx/vmx.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index e1c55ce..b1f2df8 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -2621,7 +2621,8 @@ static void vmx_idtv_reinject(unsigned long idtv_info)
>           * Clear NMI-blocking interruptibility info if an NMI delivery 
> faulted.
>           * Re-delivery will re-set it (see SDM 3B 25.7.1.2).
>           */
> -        if ( (idtv_info & INTR_INFO_INTR_TYPE_MASK) == 
> (X86_EVENTTYPE_NMI<<8) )
> +        if ( cpu_has_vmx_vnmi && ((idtv_info & INTR_INFO_INTR_TYPE_MASK) ==
> +                                 (X86_EVENTTYPE_NMI<<8)) )

This would be easier to read as

if ( cpu_has_vmx_vnmi &&
     (idtv_info & INTR_INFO_INTR_TYPE_MASK) == (X86_EVENTTYPE_NMI<<8)) )

~Andrew

>          {
>              unsigned long intr_info;
>  
> @@ -2772,8 +2773,7 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
>      hvm_maybe_deassert_evtchn_irq();
>  
>      __vmread(IDT_VECTORING_INFO, &idtv_info);
> -    if ( !nestedhvm_vcpu_in_guestmode(v) && 
> -         exit_reason != EXIT_REASON_TASK_SWITCH )
> +    if ( exit_reason != EXIT_REASON_TASK_SWITCH )
>          vmx_idtv_reinject(idtv_info);
>  
>      switch ( exit_reason )


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