On Tue, 28 Aug 2018 18:55:35 +0200
Marc-André Lureau <marcandre.lur...@gmail.com> wrote:
> On Tue, Aug 28, 2018 at 6:54 PM Marc-André Lureau
> <marcandre.lur...@gmail.com> wrote:
> >
> > Hi
> >
> > On Tue, Aug 28, 2018 at 6:49 PM Igor Mammedov <imamm...@redhat.com> wrote:
> > >
> > > On Tue, 28 Aug 2018 17:38:40 +0200
> > > Marc-André Lureau <marcandre.lur...@redhat.com> wrote:
> > >
> > > > The share=on/off property is used to modified mmap() MAP_SHARED
> > > > setting. Make it on by default for convenience and compatibility
> > > > reasons.
> > > it would be nice to state reasons here.
> > >
> > > also flipping default to on is behavioral change when
> > > used with bind policy which could make backend initialization fail
> > > so CLI that used to work (if there are any users of this without
> > > shared=on)
> > > won't work anymore.
> >
> > memfd backend is passing shared=true to memory_region_init_ram_from_fd().
> >
> > The patch allows to tweak that (instead of ignoring the property),
> > while keeping the value to shared=true.
>
> keeping the default value to shared=trrue.
ok,
another question:
does it make sense to allow "shared=false" at all?
should we bail out if user asks for it?
>
> >
> > >
> > > >
> > > > Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com>
> > > > ---
> > > > backends/hostmem-memfd.c | 4 +++-
> > > > qemu-options.hx | 4 +++-
> > > > 2 files changed, 6 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/backends/hostmem-memfd.c b/backends/hostmem-memfd.c
> > > > index 1e20fe0ba8..abd52364db 100644
> > > > --- a/backends/hostmem-memfd.c
> > > > +++ b/backends/hostmem-memfd.c
> > > > @@ -59,7 +59,8 @@ memfd_backend_memory_alloc(HostMemoryBackend
> > > > *backend, Error **errp)
> > > >
> > > > name = object_get_canonical_path(OBJECT(backend));
> > > > memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend),
> > > > - name, backend->size, true, fd,
> > > > errp);
> > > > + name, backend->size,
> > > > + backend->share, fd, errp);
> > > > g_free(name);
> > > > }
> > > >
> > > > @@ -131,6 +132,7 @@ memfd_backend_instance_init(Object *obj)
> > > >
> > > > /* default to sealed file */
> > > > m->seal = true;
> > > > + MEMORY_BACKEND(m)->share = true;
> > > > }
> > > >
> > > > static void
> > > > diff --git a/qemu-options.hx b/qemu-options.hx
> > > > index f14e423b7c..25c02d72b8 100644
> > > > --- a/qemu-options.hx
> > > > +++ b/qemu-options.hx
> > > > @@ -4029,7 +4029,7 @@ Memory backend objects offer more control than
> > > > the @option{-m} option that is
> > > > traditionally used to define guest RAM. Please refer to
> > > > @option{memory-backend-file} for a description of the options.
> > > >
> > > > -@item -object
> > > > memory-backend-memfd,id=@var{id},merge=@var{on|off},dump=@var{on|off},prealloc=@var{on|off},size=@var{size},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave},seal=@var{on|off},hugetlb=@var{on|off},hugetlbsize=@var{size}
> > > > +@item -object
> > > > memory-backend-memfd,id=@var{id},merge=@var{on|off},dump=@var{on|off},share=@var{on|off},prealloc=@var{on|off},size=@var{size},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave},seal=@var{on|off},hugetlb=@var{on|off},hugetlbsize=@var{size}
> > > >
> > > > Creates an anonymous memory file backend object, which allows QEMU to
> > > > share the memory with an external process (e.g. when using
> > > > @@ -4051,6 +4051,8 @@ with the @option{seal} option (requires at least
> > > > Linux 4.16).
> > > > Please refer to @option{memory-backend-file} for a description of the
> > > > other options.
> > > >
> > > > +The @option{share} boolean option is @var{on} by default with memfd.
> > > > +
> > > > @item -object rng-random,id=@var{id},filename=@var{/dev/random}
> > > >
> > > > Creates a random number generator backend which obtains entropy from
> > >
> > >
> >
> >
> > --
> > Marc-André Lureau
>
>
>
