Re: [Xen-devel] [PATCH] x86/debug: Plumb pending_dbg through the monitor and devicemodel interfaces

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

On Tue, Dec 3, 2019 at 1:23 PM Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
>
> On 03/12/2019 18:16, Tamas K Lengyel wrote:
> > On Tue, Dec 3, 2019 at 1:09 PM Andrew Cooper <andrew.cooper3@xxxxxxxxxx> 
> > wrote:
> >> On 03/12/2019 18:05, Tamas K Lengyel wrote:
> >>>> diff --git a/xen/include/public/vm_event.h 
> >>>> b/xen/include/public/vm_event.h
> >>>> index 959083d8c4..76676ff4c0 100644
> >>>> --- a/xen/include/public/vm_event.h
> >>>> +++ b/xen/include/public/vm_event.h
> >>>> @@ -281,6 +281,7 @@ struct vm_event_debug {
> >>>>      uint32_t insn_length;
> >>>>      uint8_t type;        /* HVMOP_TRAP_* */
> >>>>      uint8_t _pad[3];
> >>>> +    uint64_t pending_dbg;
> >>> This is just a nitpick but I would prefer if we had the _pad field as
> >>> the last element in the struct and keep all 64-bit members up in the
> >>> front.
> >> Well the reason I did it like this is that this version will continue to
> >> function with older introspection code.  The extra field is within a
> >> union and no other data moves.
> >>
> >> By repositioning to the start, it will almost certainly break older
> >> introspection code even though it compiled correctly.
> >>
> >> Your choice.
> > We are already bumping the interface version for the next release so
> > old introspection code by design will stop working. We make no ABI
> > stability guarantees between interface versions so this is a
> > non-issue.
>
> Ok fine.  Updated locally, but I won't send a new version of the patch
> just for this delta.
>
> diff --git a/xen/include/public/vm_event.h b/xen/include/public/vm_event.h
> index 76676ff4c0..8c24a58964 100644
> --- a/xen/include/public/vm_event.h
> +++ b/xen/include/public/vm_event.h
> @@ -278,10 +278,10 @@ struct vm_event_singlestep {
>
>  struct vm_event_debug {
>      uint64_t gfn;
> +    uint64_t pending_dbg;
>      uint32_t insn_length;
>      uint8_t type;        /* HVMOP_TRAP_* */
>      uint8_t _pad[3];
> -    uint64_t pending_dbg;
>  };

With the above adjustment:

Acked-by: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>

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