Re: [PATCH 4 of 4] Add a trace hypercall to allow tracing from dom0 or domU

[George Dunlap <george.dunlap@citrix.com>]

On Fri, 2011-07-15 at 16:38 +0100, Olaf Hering wrote:
> diff -r 6e4aef7b5051 -r f72dcd1b8bbd xen/include/public/trace.h
> --- a/xen/include/public/trace.h
> +++ b/xen/include/public/trace.h
> @@ -26,6 +26,8 @@
>  #ifndef __XEN_PUBLIC_TRACE_H__
>  #define __XEN_PUBLIC_TRACE_H__
>  
> +#include "xen.h"
> +
>  #define TRACE_EXTRA_MAX    7
>  #define TRACE_EXTRA_SHIFT 28
>  
> @@ -65,6 +67,7 @@
>  #define TRC_LOST_RECORDS        (TRC_GEN + 1)
>  #define TRC_TRACE_WRAP_BUFFER  (TRC_GEN + 2)
>  #define TRC_TRACE_CPU_CHANGE    (TRC_GEN + 3)
> +#define TRC_TRACE_GUEST_HYPERCALL (TRC_GEN + 4)

Looks like perhaps a leftover from an earlier patch? :-)

> diff -r 6e4aef7b5051 -r f72dcd1b8bbd xen/include/public/xen.h
> --- a/xen/include/public/xen.h
> +++ b/xen/include/public/xen.h
> @@ -94,6 +94,7 @@ DEFINE_XEN_GUEST_HANDLE(xen_pfn_t);
>  #define __HYPERVISOR_kexec_op             37
>  #define __HYPERVISOR_tmem_op              38
>  #define __HYPERVISOR_xc_reserved_op       39 /* reserved for XenClient */
> +#define __HYPERVISOR_xentrace_op          40

Seems unnecessary to make a whole hypercall just for this one thing, but
I'll defer to Keir's judgement on that.  At very least, it should accept
an "op" command, of which "trace" is just one, so that it's expandable
in the future without breaking backwards compatibility.

Other than that, looks good -- thanks for doing this.

 -George