Re: [Xen-devel] [PATCH 4/4] xen: Add V4V implementation

[Tim Deegan <tim@xxxxxxx>]

At 16:03 +0100 on 04 Oct (1349366589), Jean Guyader wrote:
> On 4 October 2012 13:11, Jan Beulich <JBeulich@xxxxxxxx> wrote:
> >>>> On 04.10.12 at 14:03, Jean Guyader <jean.guyader@xxxxxxxxx> wrote:
> >> On 20 September 2012 13:20, Jan Beulich <JBeulich@xxxxxxxx> wrote:
> >>>>>> On 20.09.12 at 13:42, Jean Guyader <jean.guyader@xxxxxxxxxx> wrote:
> >>>>+        case V4VOP_register_ring:
> >>>>+            {
> >>>>+                XEN_GUEST_HANDLE(v4v_ring_t) ring_hnd =
> >>>>+                    guest_handle_cast(arg1, v4v_ring_t);
> >>>>+                XEN_GUEST_HANDLE(xen_pfn_t) pfn_hnd =
> >>>>+                    guest_handle_cast(arg2, xen_pfn_t);
> >>>>+                uint32_t npage = arg3;
> >>>>+                if ( unlikely(!guest_handle_okay(ring_hnd, 1)) )
> >>>>+                    goto out;
> >>>>+                if ( unlikely(!guest_handle_okay(pfn_hnd, npage)) )
> >>>>+                    goto out;
> >>>
> >>> Here and below - this isn't sufficient for compat guests, or else
> >>> you give them a way to point into the compat m2p table.
> >>>
> >>
> >> I'll probably switch to uint64_t for the v4v mfn list instead of using
> >> xen_pfn_t which
> >> are unsigned long. That way I can save the need for a compat wrapper.
> >
> > But that comment of yours doesn't address the problem I pointed
> > out.
> >
> 
> [Resent, CCing everyone this time]
> 
> I'm sorry, I don't really get what you mean them. I've tried to get
> all my struct
> layout such as all the offset for the field are the same for 64b and 32b, this
> way I thought I could get away with doing a compat wrapper.

Even if the args don't need translation, compat-mode guests have
different VA layouts and need different range checks (though I'm not
sure why these aren't automatically adjusted based on current).

AIUI you need to use compat_handle_okay() instead of guest_handle_okay()
to check the handles if is_pv_32on64_domain(current).

Tim.

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