Re: [Xen-devel] [PATCH v6 5/5] x86/vm_event: Add HVM debug exception vm_events

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Tamas K Lengyel [mailto:tamas@xxxxxxxxxxxxx]
> Sent: Friday, June 24, 2016 1:07 AM
> 
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index 03fcba7..4b69ca6 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -3373,10 +3373,39 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
>              HVMTRACE_1D(TRAP_DEBUG, exit_qualification);
>              write_debugreg(6, exit_qualification | DR_STATUS_RESERVED_ONE);
>              if ( !v->domain->debugger_attached )
> -                vmx_propagate_intr(intr_info);
> +            {
> +                unsigned long insn_len = 0;
> +                int rc;
> +                unsigned long trap_type = MASK_EXTR(intr_info,
> +                                                    
> INTR_INFO_INTR_TYPE_MASK);
> +
> +                if ( trap_type >= X86_EVENTTYPE_SW_INTERRUPT )
> +                    __vmread(VM_EXIT_INSTRUCTION_LEN, &insn_len);
> +
> +                rc = hvm_monitor_debug(regs->eip,
> +                                       HVM_MONITOR_DEBUG_EXCEPTION,
> +                                       trap_type, insn_len);
> +
> +                /*
> +                 * !rc  continue normally
> +                 * rc > paused waiting for response, work here is done

Did you mean "rc > 0, vcpu is paused and waiting for response..."? Please
make the comment clear to understand.

> +                 * rc < error, fall-through to exit_and_crash
> +                 */
> +                if ( !rc )
> +                {
> +                    vmx_propagate_intr(intr_info);
> +                    break;
> +                }
> +                if ( rc > 0 )
> +                    break;
> +            }
>              else
> +            {
>                  domain_pause_for_debugger();
> -            break;
> +                break;
> +            }
> +
> +            goto exit_and_crash;

Putting goto as the last line within a 'case' looks a bit strange. What
about putting goto directly under a "if ( rc < 0 )" check earlier?

                if ( !rc )
                        ...
                if ( rc < 0 )
                        goto exit_and_crash;
        }
        else
                domain_pause_for_debugger();
        break;

Thanks
Kevin

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