Re: [Xen-devel] [PATCH v2 5/5] xen: replace XEN_GUEST_HANDLE with XEN_GUEST_HANDLE_PARAM when appropriate

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Tue, 14 Aug 2012, Stefano Stabellini wrote:
> On Mon, 13 Aug 2012, Jan Beulich wrote:
> > >>> On 13.08.12 at 13:24, Stefano Stabellini 
> > >>> <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> > > On the other hand if you mean casting a XEN_GUEST_HANDLE_PARAM into a
> > > XEN_GUEST_HANDLE to pass it to other internal functions, I don't think
> > > there is any point in that because the other internal functions should
> > > also have XEN_GUEST_HANDLE_PARAMs as parameters.
> > 
> > So you obviously need a cast from "normal" to _PARAM (so that
> > you can pass embedded fields to functions).
> 
> In practice embedded fields are in guest memory, so the first thing Xen
> does is calling copy_from_guest and work with the struct pointer
> directly from that point on.
> 
> However I do see how a function like that might make the distinction
> between XEN_GUEST_HANDLE and XEN_GUEST_HANDLE_PARAMs clearer, so I'll
> add one.
> 
> The implementation is going to identical to guest_handle_cast though.
> 

Actually it is probably better to add a good comment on top of
guest_handle_cast explaining that can be used with both XEN_GUEST_HANDLE
or XEN_GUEST_HANDLE_PARAM as paramters.

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