Re: [Xen-devel] [PATCH 0/5] ARM hypercall ABI: 64 bit ready

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 6 Aug 2012, David Vrabel wrote:
> On 06/08/12 15:11, Stefano Stabellini wrote:
> > Hi all,
> > this patch series makes the necessary changes to make sure that the
> > current ARM hypercall ABI can be used as-is on 64 bit ARM platforms:
> > 
> > - it defines xen_ulong_t as uint64_t on ARM;
> > - it introduces a new macro to handle guest pointers, called
> > XEN_GUEST_HANDLE_PARAM (that has size 4 bytes on aarch and is going to
> > have size 8 bytes on aarch64);
> > - it replaces all the occurrences of XEN_GUEST_HANDLE in hypercall
> > parameters with XEN_GUEST_HANDLE_PARAM.
> 
> This is a subtle (and undocumented!) distinction. I can see people
> adding/modifying hypercall etc. getting this wrong and no one noticing
> for a while (since it doesn't affect x86).

Where should I document this? I wrote it into the commit message but
maybe a doc under docs is better.


> The xen_ulong_t parameters (when used for pointers) from an aarch guest
> point of view are a uint32_t guest pointer and uint32_t of padding.  So
> the guest handles will be the same size in hypercall parameters and
> structure members.

I changed xen_ulong_t to be 64 bit on ARM

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