Re: [Qemu-devel] vhost-user: broken mem regions

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jun 25, 2014 at 09:13:36PM +0300, Nikolay Nikolaev wrote:
> On Wed, Jun 25, 2014 at 9:07 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > On Wed, Jun 25, 2014 at 07:56:46PM +0300, Nikolay Nikolaev wrote:
> >> On Wed, Jun 25, 2014 at 7:44 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
> >> >> nregions: 4
> >> >> region:
> >> >>       gpa = 0x100000000
> >> >>       size = 3221225472
> >> >>       ua = 0x2aab6ac00000
> >> >
> >> > High memory, above 3 gigabytes.
> >> >
> >> >> region:
> >> >>       gpa = 0xFFFC0000
> >> >>       size = 262144
> >> >>       ua = 0x7fc13d200000
> >> >
> >> > This is the BIOS.  There shouldn't be any FD for this one, it
> >> > is not allocated in hugetlbfs.
> >> >
> >> >> region:
> >> >>       gpa = 0x0
> >> >>       size = 655360
> >> >>       ua = 0x2aaaaac00000
> >> >> region:
> >> >>       gpa = 0xC0000
> >> >>       size = 3220439040
> >> >>       ua = 0x2aaaaacc0000
> >> >
> >> > Together, it's the first 3 GB of memory.
> >> >
> >> > I understand now what you mean.  Yeah, the format should be changed
> >> > to include the offset (why does vhost-user need the ua at all?
> >> The vring addresses are QEMU UA addresses. Of course vhost-user can
> >> translate them to guest physical before sending the message.
> >
> > It seems useful to have them as QEMU UA, this will allow
> > frontends other than virtio where QEMU operates the
> > ring.
> 
> OK - so there will be a new offset field. That's fine with me. What
> would be the deadline for such change?
> It's not exactly bugfix. On the other hand there's no wide adoption of
> the protocol so it's still not critical to change it.

Right. So you have to do this before the hard freeze.
And don't cut it too fine either :)

> >
> >> > perhaps the offset can replace the ua).
> >> >
> >> >> BTW Any idea what to do with region 2, it doesn’t look like the one belonging
> >> >> to the same place, but qemu_get_ram_fd() returns same FD for it.
> >> >
> >> > This must be a bug.  I would have expected qemu_get_ram_fd to return -1
> >> > here, so no descriptor should be passed to vhost-user.
> >> >
> >> > Paolo