On Thu, Jan 19, 2017 at 01:44:36AM +0000, Li, Liang Z wrote:
> > > > > + *range = cpu_to_le64((base_pfn <<
> > > > > + VIRTIO_BALLOON_NR_PFN_BITS) | 0);
> > > > > + *(range + 1) = cpu_to_le64(pages);
> > > > > + vb->resp_pos += 2;
> > > >
> > > > Pls use structs for this kind of stuff.
> > >
> > > I am not sure if you mean to use
> > >
> > > struct range {
> > > __le64 pfn: 52;
> > > __le64 nr_page: 12
> > > }
> > > Instead of the shift operation?
> >
> > Not just that. You want to add a pages field as well.
> >
>
> pages field? Could you give more hints?
Well look how you are formatting it manually above.
There is clearly a structure with two 64 bit fields.
First one includes pfn and 0 (no idea why does | 0 make
sense but that's a separate issue).
Second one includes the pages value.
> > Generally describe the format in the header in some way so host and guest
> > can easily stay in sync.
>
> 'VIRTIO_BALLOON_NR_PFN_BITS' is for this purpose and it will be passed to the
> related function in page_alloc.c as a parameter.
>
> Thanks!
> Liang
> > All the pointer math and void * means we get zero type safety and I'm not
> > happy about it.
> >
> > It's not good that virtio format seeps out to page_alloc anyway.
> > If unavoidable it is not a good idea to try to hide this fact, people will assume
> > they can change the format at will.
> >
> > --
> > MST
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