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

[Jean Guyader <jean.guyader@xxxxxxxxx>]

On 4 October 2012 16:12, Tim Deegan <tim@xxxxxxx> wrote:
> 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).
>

How about something like that?

Jean

Attachment: guest_handle_okay_maybe_compat.patch
Description: Binary data

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