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Date: Wed, 25 Jun 2014 21:07:18 +0300
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] vhost-user: broken mem regions
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To: Nikolay Nikolaev <n.nikolaev@virtualopensystems.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>, "Damjan Marion (damarion)" <damarion@cisco.com>, qemu-devel <qemu-devel@nongnu.org>

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> wr=
ote:
> >> nregions: 4
> >> region:
> >>       gpa =3D 0x100000000
> >>       size =3D 3221225472
> >>       ua =3D 0x2aab6ac00000
> >
> > High memory, above 3 gigabytes.
> >
> >> region:
> >>       gpa =3D 0xFFFC0000
> >>       size =3D 262144
> >>       ua =3D 0x7fc13d200000
> >
> > This is the BIOS.  There shouldn't be any FD for this one, it
> > is not allocated in hugetlbfs.
> >
> >> region:
> >>       gpa =3D 0x0
> >>       size =3D 655360
> >>       ua =3D 0x2aaaaac00000
> >> region:
> >>       gpa =3D 0xC0000
> >>       size =3D 3220439040
> >>       ua =3D 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.

> > perhaps the offset can replace the ua).
> >
> >> BTW Any idea what to do with region 2, it doesn=E2=80=99t 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