Re: [PATCH v2 2/3] memory: Allow a MemoryRegion to be marked no_vhost

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

On Tue, Jan 14, 2020 at 11:26:08AM +0000, Dr. David Alan Gilbert wrote:
> * Michael S. Tsirkin (mst@redhat.com) wrote:
> > On Mon, Jan 13, 2020 at 05:36:46PM +0000, Dr. David Alan Gilbert (git) wrote:
> > > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> > > 
> > > Allow a memory region to be marked as 'no_vhost' and
> > > exclude that region from vhost's list build.
> > > 
> > > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > 
> > I thought we agreed vfio needs this as well?
> > I'd rather this had some meaning not just "no vhost" ...
> > no_dma?
> 
> VFIO tends to be unplugged on migration anyway (at the moment);

But it still should ignore synic, right?

> but I'm happy to change the name if everyone is happy with the rest of
> the series and we can agree on the new name,
> 
> Dave
> 
> > > ---
> > >  hw/virtio/vhost.c     |  3 ++-
> > >  include/exec/memory.h | 21 +++++++++++++++++++++
> > >  memory.c              | 15 +++++++++++++++
> > >  3 files changed, 38 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> > > index 774d87d98e..462498bfe6 100644
> > > --- a/hw/virtio/vhost.c
> > > +++ b/hw/virtio/vhost.c
> > > @@ -402,7 +402,8 @@ static bool vhost_section(struct vhost_dev *dev, MemoryRegionSection *section)
> > >      bool log_dirty = memory_region_get_dirty_log_mask(section->mr) &
> > >                       ~(1 << DIRTY_MEMORY_MIGRATION);
> > >      result = memory_region_is_ram(section->mr) &&
> > > -        !memory_region_is_rom(section->mr);
> > > +             !memory_region_is_rom(section->mr) &&
> > > +             !memory_region_get_no_vhost(section->mr);
> > >  
> > >      /* Vhost doesn't handle any block which is doing dirty-tracking other
> > >       * than migration; this typically fires on VGA areas.
> > > diff --git a/include/exec/memory.h b/include/exec/memory.h
> > > index aef8123d48..f475c06d63 100644
> > > --- a/include/exec/memory.h
> > > +++ b/include/exec/memory.h
> > > @@ -394,6 +394,7 @@ struct MemoryRegion {
> > >      bool ram_device;
> > >      bool enabled;
> > >      bool warning_printed; /* For reservations */
> > > +    bool no_vhost;
> > >      uint8_t vga_logging_count;
> > >      MemoryRegion *alias;
> > >      hwaddr alias_offset;
> > > @@ -1625,6 +1626,26 @@ void memory_region_set_readonly(MemoryRegion *mr, bool readonly);
> > >   */
> > >  void memory_region_set_nonvolatile(MemoryRegion *mr, bool nonvolatile);
> > >  
> > > +/**
> > > + * memory_region_set_no_vhost: Make vhost ignore a memory region
> > > + *
> > > + * Makes vhost ignore a memory region, useful if it isn't real
> > > + * DMAble memory and is at inconvenient addresses
> > > + *
> > > + * @mr: the region being updated.
> > > + * @no_vhost: true to ignore
> > > + */
> > > +void memory_region_set_no_vhost(MemoryRegion *mr, bool no_vhost);
> > > +
> > > +/**
> > > + * memory_region_set_no_vhost: Test if memory region is marked no vhost
> > > + *
> > > + * Test if the no_vhost flag is set on the memory region
> > > + *
> > > + * @mr: the region being tested.
> > > + */
> > > +bool memory_region_get_no_vhost(const MemoryRegion *mr);
> > > +
> > >  /**
> > >   * memory_region_rom_device_set_romd: enable/disable ROMD mode
> > >   *
> > > diff --git a/memory.c b/memory.c
> > > index d7b9bb6951..9371998e30 100644
> > > --- a/memory.c
> > > +++ b/memory.c
> > > @@ -2136,6 +2136,21 @@ void memory_region_set_nonvolatile(MemoryRegion *mr, bool nonvolatile)
> > >      }
> > >  }
> > >  
> > > +void memory_region_set_no_vhost(MemoryRegion *mr, bool no_vhost)
> > > +{
> > > +    if (mr->no_vhost != no_vhost) {
> > > +        memory_region_transaction_begin();
> > > +        mr->no_vhost = no_vhost;
> > > +        memory_region_update_pending |= mr->enabled;
> > > +        memory_region_transaction_commit();
> > > +    }
> > > +}
> > > +
> > > +bool memory_region_get_no_vhost(const MemoryRegion *mr)
> > > +{
> > > +    return mr->no_vhost;
> > > +}
> > > +
> > >  void memory_region_rom_device_set_romd(MemoryRegion *mr, bool romd_mode)
> > >  {
> > >      if (mr->romd_mode != romd_mode) {
> > > -- 
> > > 2.24.1
> > 
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK