Re: [Qemu-devel] [RfC PATCH 5/6] vfio/display: adding region support

[Gerd Hoffmann <kraxel@redhat.com>]

  Hi,

> > +    ret = ioctl(vdev->vbasedev.fd, VFIO_DEVICE_QUERY_GFX_PLANE,
> > &plane);
> > +    if (ret < 0) {
> > +        fprintf(stderr, "ioctl VFIO_DEVICE_QUERY_GFX_PLANE: %s\n",
> > +                strerror(errno));
> 
> %m?

Oh, neat, didn't know this even exists.

man page says it is a glibc extension though.  So do we really want use
it in a portable code base?  In this specific case it would probably
not cause any trouble though as vfio is linux-only anyway.

> > +    if (vdev->region_mmap == NULL) {
> > +        /* mmap region */
> > +        ret = vfio_get_region_info(&vdev->vbasedev,
> > plane.region_index,
> > +                                   &region);
> > +        if (ret != 0) {
> > +            fprintf(stderr, "%s: vfio_get_region_info(%d): %s\n",
> > +                    __func__, plane.region_index, strerror(-ret));
> > +            return;
> > +        }
> > +        vdev->region_size = region->size;
> > +        vdev->region_mmap = mmap(NULL, region->size,
> > +                                 PROT_READ, MAP_SHARED,
> > +                                 vdev->vbasedev.fd,
> > +                                 region->offset);
> > +        if (vdev->region_mmap == MAP_FAILED) {
> > +            fprintf(stderr, "%s: mmap region %d: %s\n", __func__,
> > +                    plane.region_index, strerror(errno));
> > +            vdev->region_mmap = NULL;
> > +            g_free(region);
> > +            return;
> > +        }
> 
> Seems like we should really try to use a VFIORegion for this.

IIRC I checked this, but it didn't look straight forward as VFIORegion
is designed for guest access not host access.

cheers,
  Gerd