Re: [Xen-devel] Should we revert "mm: New XENMEM space, XENMAPSPACE_gmfn_range"?

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.08.12 at 15:13, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
wrote:
> On Thu, 2 Aug 2012, Jan Beulich wrote:
>> >>> On 01.08.12 at 19:55, Stefano Stabellini 
>> >>> <stefano.stabellini@xxxxxxxxxxxxx> 
> wrote:
>> > I was reading more about this commit because this patch breaks the ABI
>> > on ARM, when I realized that on x86 there is no standard that specifies
>> > the alignment of fields in a struct.
>> 
>> There is - the psABI supplements to the SVR4 ABI.
> 
> Thank you very much, that document was exactly what I was looking for.
> 
> Also it explains where my confusion was coming from: Jean's patch doesn't
> break the ABI on ARM or x86, but I am carrying a patch in my patch queue
> that does (unless Jean's patch is applied):
> 
> http://marc.info/?l=xen-devel&m=134305777903771 
> 
> As you can see this patch splits .space into two shorts, and as a side
> effect changes the offset of .space, removing the padding.
> Thus it led me to think that Jean's patch was breaking the ABI when actually
> with "arm: initial XENMAPSPACE_gmfn_foreign" applied, it becomes
> required to keep the binary interface compatible.

And then you wouldn't need to split 'space' and break the ABI
at all, you could simply put 'size' and 'foreign_domid' into a union.

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel