Re: [PATCH 2/2] hyperv/synic: Allocate as ram_device

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Roman Kagan (rkagan@virtuozzo.com) wrote:
> On Wed, Jan 08, 2020 at 01:53:53PM +0000, Dr. David Alan Gilbert (git) wrote:
> > Mark the synic pages as ram_device so that they won't be visible
> > to vhost.
> 
> Unless I'm misreading the code this also makes them invisible to
> migration.
> 
> I need some more reading on the ram_device region behavior to better
> understand other potential consequences.

Hmm you might be right; that's not intended.
Looking at memory.c I see we have vmstate_register_ram calls in
  memory_region_init_ram
  memory_region_init_rom
  memory_region_init_rom_device

but not
  memory_region_init_ram_device_ptr

hmm; OK this needs changing then.

Dave

> Thanks,
> Roman.
> 
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> >  hw/hyperv/hyperv.c | 14 ++++++++------
> >  1 file changed, 8 insertions(+), 6 deletions(-)
> > 
> > diff --git a/hw/hyperv/hyperv.c b/hw/hyperv/hyperv.c
> > index da8ce82725..4de3ec411d 100644
> > --- a/hw/hyperv/hyperv.c
> > +++ b/hw/hyperv/hyperv.c
> > @@ -95,12 +95,14 @@ static void synic_realize(DeviceState *dev, Error **errp)
> >      msgp_name = g_strdup_printf("synic-%u-msg-page", vp_index);
> >      eventp_name = g_strdup_printf("synic-%u-event-page", vp_index);
> >  
> > -    memory_region_init_ram(&synic->msg_page_mr, obj, msgp_name,
> > -                           sizeof(*synic->msg_page), &error_abort);
> > -    memory_region_init_ram(&synic->event_page_mr, obj, eventp_name,
> > -                           sizeof(*synic->event_page), &error_abort);
> > -    synic->msg_page = memory_region_get_ram_ptr(&synic->msg_page_mr);
> > -    synic->event_page = memory_region_get_ram_ptr(&synic->event_page_mr);
> > +    synic->msg_page = qemu_memalign(qemu_real_host_page_size,
> > +                                    sizeof(*synic->msg_page));
> > +    synic->event_page = qemu_memalign(qemu_real_host_page_size,
> > +                                      sizeof(*synic->event_page));
> > +    memory_region_init_ram_device_ptr(&synic->msg_page_mr, obj, msgp_name,
> > +                           sizeof(*synic->msg_page), synic->msg_page);
> > +    memory_region_init_ram_device_ptr(&synic->event_page_mr, obj, eventp_name,
> > +                           sizeof(*synic->event_page), synic->event_page);
> >  
> >      g_free(msgp_name);
> >      g_free(eventp_name);
> > -- 
> > 2.24.1
> > 
> > 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK