Re: [Xen-devel] [XEN PATCH v3] x86/vm_event: add short-circuit for breakpoints (aka, , "fast single step")

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

> diff --git a/xen/include/public/vm_event.h b/xen/include/public/vm_event.h
> index aa54c86325..cb577a7ba9 100644
> --- a/xen/include/public/vm_event.h
> +++ b/xen/include/public/vm_event.h
> @@ -110,6 +110,11 @@
>   * interrupt pending after resuming the VCPU.
>   */
>  #define VM_EVENT_FLAG_GET_NEXT_INTERRUPT (1 << 10)
> +/*
> + * Execute fast singlestepping on vm_event response.
> + * Requires the vCPU to be paused already (synchronous events only).
> + */

Please expand this description here that it also requires setting the
p2midx field of fast_singlestep to which Xen will switch the vCPU to
on the occurance of the first singlestep, after which singlestep gets
automatically disabled.

> +#define VM_EVENT_FLAG_FAST_SINGLESTEP  (1 << 11)
>
>  /*
>   * Reasons for the vm event request
> @@ -276,6 +281,10 @@ struct vm_event_singlestep {
>      uint64_t gfn;
>  };
>
> +struct vm_event_fast_singlestep {
> +    uint16_t p2midx;
> +};
> +
>  struct vm_event_debug {
>      uint64_t gfn;
>      uint32_t insn_length;
> @@ -363,6 +372,7 @@ typedef struct vm_event_st {
>          struct vm_event_mov_to_msr            mov_to_msr;
>          struct vm_event_desc_access           desc_access;
>          struct vm_event_singlestep            singlestep;
> +        struct vm_event_fast_singlestep       fast_singlestep;
>          struct vm_event_debug                 software_breakpoint;
>          struct vm_event_debug                 debug_exception;
>          struct vm_event_cpuid                 cpuid;
> --
> 2.20.1

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