Re: [Xen-devel] [PATCH 5/5] xen: Add V4V implementation - padding question

[Ross Philipson <ross.philipson@xxxxxxxxxx>]

On 06/11/2013 01:25 PM, Tim Deegan wrote:
> At 13:10 -0400 on 11 Jun (1370956242), Ross Philipson wrote:
> > > > > ...
> > > > > +struct v4v_info
> > > > > +{
> > > > > +    uint64_t ring_magic;
> > > > > +    uint64_t data_magic;
> > > > > +    evtchn_port_t evtchn;
> > > > Missing padding at the end?
> > > ack.
> > At one point during the review of an earlier version of the V4V patch
> > set, Jan requested that this pad be added to the v4v_info struct. I
> > understand the padding in all the other structs but I don't understand
> > this one. This struct is not included in any other structs and is not
> > followed by any data.
> 64-bit Xen would see this as a 24-byte struct, even without explicit
> padding.  That would surprise a 32-bit guest that allocated what it saw
> as a 20-byte struct for Xen to copy into.
Ah yes, of course. Thanks for the quick response.

Ross

> Tim.

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