Re: [Xen-devel] [PATCH] RFC: Use memops for mem paging, sharing, and access, instead of domctls

[Tim Deegan <tim@xxxxxxx>]

At 08:04 -0800 on 12 Jan (1326355474), Andres Lagar-Cavilla wrote:
> > On Wed, Jan 11, Andres Lagar-Cavilla wrote:
> >
> >> +++ b/xen/include/public/domctl.h
> >
> >> +/* Use for teardown/setup of helper<->hypervisor interface for paging,
> >> + * access and sharing.*/
> >>  struct xen_domctl_mem_event_op {
> >>      uint32_t       op;           /* XEN_DOMCTL_MEM_EVENT_OP_*_* */
> >>      uint32_t       mode;         /* XEN_DOMCTL_MEM_EVENT_OP_* */
> >>
> >> -    union {
> >> -        /* OP_ENABLE IN:  Virtual address of shared page */
> >> -        uint64_aligned_t shared_addr;
> >> -        /* PAGING_PREP IN: buffer to immediately fill page in */
> >> -        uint64_aligned_t buffer;
> >> -    } u;
> >> +    uint64_aligned_t shared_addr;  /* IN:  Virtual address of shared
> >> page */
> >>      uint64_aligned_t ring_addr;    /* IN:  Virtual address of ring page
> >> */
> >>
> >> -    /* Other OPs */
> >> -    uint64_aligned_t gfn;          /* IN:  gfn of page being operated
> >> on */
> >> +    /* For binary backwards compatibility */
> >> +    uint64_aligned_t pad;
> >>  };
> >
> > Assuming this struct is routed through libxc, and libxc gets a new
> > SONAME for every release, doesnt this mean that every old binary has to
> > be recompiled anyway for the new release?
> > If so, the padding is not needed.
> Agreed, basically. Waiting to hear from tools maintainers about best
> approach to libxc.
> 
> It seems that there aren't that many users relying on a fixed ABI, so we
> can (still, until 4.2) change things. But obviously I want to be careful.

Ping?

Tim.

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