Re: [PATCH 7/7] vfio/pci: Remove map-on-fault behavior

[Alex Williamson]

On Tue, 10 Aug 2021 16:54:19 -0400
Peter Xu <peterx@xxxxxxxxxx> wrote:

> On Thu, Aug 05, 2021 at 11:08:21AM -0600, Alex Williamson wrote:
> > diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
> > index 0aa542fa1e26..9aedb78a4ae3 100644
> > --- a/drivers/vfio/pci/vfio_pci_private.h
> > +++ b/drivers/vfio/pci/vfio_pci_private.h
> > @@ -128,6 +128,7 @@ struct vfio_pci_device {
> >  	bool			needs_reset;
> >  	bool			nointx;
> >  	bool			needs_pm_restore;
> > +	bool			zapped_bars;  
> 
> Would it be nicer to invert the meaning of "zapped_bars" and rename it to
> "memory_enabled"?  Thanks,

I think this has it's own down sides, for example is this really less
confusing?:

  if (!vdev->memory_enabled && __vfio_pci_memory_enabled(vdev))

Are you specifically trying to invert the polarity or just get away
from the name proposed here?  We could use something like
"bars_unmapped", which would have the same polarity (OTOH,
"bars_mapped" suggests something to me about whether the user has
performed any mmaps of BARs).

I do wish there was a more elegant solution than an @var tracking this
state in general, but I haven't come up with such a solution yet.
Thanks,

Alex