On Wed, Jan 18, 2017 at 04:56:58AM +0000, Li, Liang Z wrote:
> > > - virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
> > > - virtqueue_kick(vq);
> > > +static void do_set_resp_bitmap(struct virtio_balloon *vb,
> > > + unsigned long base_pfn, int pages)
> > >
> > > - /* When host has read buffer, this completes via balloon_ack */
> > > - wait_event(vb->acked, virtqueue_get_buf(vq, &len));
> > > +{
> > > + __le64 *range = vb->resp_data + vb->resp_pos;
> > >
> > > + if (pages > (1 << VIRTIO_BALLOON_NR_PFN_BITS)) {
> > > + /* when the length field can't contain pages, set it to 0 to
> >
> > /*
> > * Multi-line
> > * comments
> > * should look like this.
> > */
> >
> > Also, pls start sentences with an upper-case letter.
> >
>
> Sorry for that.
>
> > > + * indicate the actual length is in the next __le64;
> > > + */
> >
> > This is part of the interface so should be documented as such.
> >
> > > + *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.
Generally describe the format in the header in some way
so host and guest can easily stay in sync.
All the pointer math and void * means we get zero type
safety and I'm not happy about it.
> I didn't use this way because I don't want to include 'virtio-balloon.h' in page_alloc.c,
> or copy the define of this struct in page_alloc.c
>
> Thanks!
> Liang
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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