From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

My rework of section adding combines overlapping or abutting regions,
but checks they're actually the same underlying RAM block.
Fix the case where two blocks abut but don't overlap; that new region
should get added (but not combined), but my previous patch was disallowing it.

Fixes: c1ece84e7c9

Reported-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 hw/virtio/vhost.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 250f886acb..fc9062a89f 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -595,10 +595,15 @@ static void vhost_region_add_section(struct vhost_dev *dev,
                                         prev_sec->offset_within_address_space,
                                         prev_sec->offset_within_region);
             } else {
-                error_report("%s: Overlapping but not coherent sections "
-                             "at %"PRIx64,
-                             __func__, mrs_gpa);
-                return;
+                /* abutting regions are fine, but overlapping ones with
+                 * different blocks/offsets shouldn't happen
+                 */
+                if (mrs_gpa != prev_gpa_end + 1) {
+                    error_report("%s: Overlapping but not coherent sections "
+                                 "at %"PRIx64,
+                                 __func__, mrs_gpa);
+                    return;
+                }
             }
         }
     }
-- 
2.14.3

On Fri, Mar 23, 2018 at 12:46:37PM +0000, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> My rework of section adding combines overlapping or abutting regions,
> but checks they're actually the same underlying RAM block.
> Fix the case where two blocks abut but don't overlap; that new region
> should get added (but not combined), but my previous patch was disallowing it.
> 
> Fixes: c1ece84e7c9
> 
> Reported-by: Alex Williamson <alex.williamson@redhat.com>
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Can we replace abutting with adjacent pls?

> ---
>  hw/virtio/vhost.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 250f886acb..fc9062a89f 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -595,10 +595,15 @@ static void vhost_region_add_section(struct vhost_dev *dev,
>                                          prev_sec->offset_within_address_space,
>                                          prev_sec->offset_within_region);
>              } else {
> -                error_report("%s: Overlapping but not coherent sections "
> -                             "at %"PRIx64,
> -                             __func__, mrs_gpa);
> -                return;
> +                /* abutting regions are fine, but overlapping ones with
> +                 * different blocks/offsets shouldn't happen
> +                 */
> +                if (mrs_gpa != prev_gpa_end + 1) {
> +                    error_report("%s: Overlapping but not coherent sections "
> +                                 "at %"PRIx64,
> +                                 __func__, mrs_gpa);
> +                    return;
> +                }
>              }
>          }
>      }
> -- 
> 2.14.3

* Michael S. Tsirkin (mst@redhat.com) wrote:
> On Fri, Mar 23, 2018 at 12:46:37PM +0000, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> > 
> > My rework of section adding combines overlapping or abutting regions,
> > but checks they're actually the same underlying RAM block.
> > Fix the case where two blocks abut but don't overlap; that new region
> > should get added (but not combined), but my previous patch was disallowing it.
> > 
> > Fixes: c1ece84e7c9
> > 
> > Reported-by: Alex Williamson <alex.williamson@redhat.com>
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> 
> Can we replace abutting with adjacent pls?

Sure; do you want to fix that in commit?

Dave

> > ---
> >  hw/virtio/vhost.c | 13 +++++++++----
> >  1 file changed, 9 insertions(+), 4 deletions(-)
> > 
> > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> > index 250f886acb..fc9062a89f 100644
> > --- a/hw/virtio/vhost.c
> > +++ b/hw/virtio/vhost.c
> > @@ -595,10 +595,15 @@ static void vhost_region_add_section(struct vhost_dev *dev,
> >                                          prev_sec->offset_within_address_space,
> >                                          prev_sec->offset_within_region);
> >              } else {
> > -                error_report("%s: Overlapping but not coherent sections "
> > -                             "at %"PRIx64,
> > -                             __func__, mrs_gpa);
> > -                return;
> > +                /* abutting regions are fine, but overlapping ones with
> > +                 * different blocks/offsets shouldn't happen
> > +                 */
> > +                if (mrs_gpa != prev_gpa_end + 1) {
> > +                    error_report("%s: Overlapping but not coherent sections "
> > +                                 "at %"PRIx64,
> > +                                 __func__, mrs_gpa);
> > +                    return;
> > +                }
> >              }
> >          }
> >      }
> > -- 
> > 2.14.3
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

On Fri, Mar 23, 2018 at 02:53:38PM +0000, Dr. David Alan Gilbert wrote:
> * Michael S. Tsirkin (mst@redhat.com) wrote:
> > On Fri, Mar 23, 2018 at 12:46:37PM +0000, Dr. David Alan Gilbert (git) wrote:
> > > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> > > 
> > > My rework of section adding combines overlapping or abutting regions,
> > > but checks they're actually the same underlying RAM block.
> > > Fix the case where two blocks abut but don't overlap; that new region
> > > should get added (but not combined), but my previous patch was disallowing it.
> > > 
> > > Fixes: c1ece84e7c9
> > > 
> > > Reported-by: Alex Williamson <alex.williamson@redhat.com>
> > > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > 
> > Can we replace abutting with adjacent pls?
> 
> Sure; do you want to fix that in commit?
> 
> Dave

Rather.

> > > ---
> > >  hw/virtio/vhost.c | 13 +++++++++----
> > >  1 file changed, 9 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> > > index 250f886acb..fc9062a89f 100644
> > > --- a/hw/virtio/vhost.c
> > > +++ b/hw/virtio/vhost.c
> > > @@ -595,10 +595,15 @@ static void vhost_region_add_section(struct vhost_dev *dev,
> > >                                          prev_sec->offset_within_address_space,
> > >                                          prev_sec->offset_within_region);
> > >              } else {
> > > -                error_report("%s: Overlapping but not coherent sections "
> > > -                             "at %"PRIx64,
> > > -                             __func__, mrs_gpa);
> > > -                return;
> > > +                /* abutting regions are fine, but overlapping ones with
> > > +                 * different blocks/offsets shouldn't happen
> > > +                 */
> > > +                if (mrs_gpa != prev_gpa_end + 1) {
> > > +                    error_report("%s: Overlapping but not coherent sections "
> > > +                                 "at %"PRIx64,
> > > +                                 __func__, mrs_gpa);
> > > +                    return;
> > > +                }
> > >              }
> > >          }
> > >      }
> > > -- 
> > > 2.14.3
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

On Fri, Mar 23, 2018 at 12:46:37PM +0000, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> My rework of section adding combines overlapping or abutting regions,
> but checks they're actually the same underlying RAM block.
> Fix the case where two blocks abut but don't overlap; that new region
> should get added (but not combined), but my previous patch was disallowing it.
> 
> Fixes: c1ece84e7c9
> 
> Reported-by: Alex Williamson <alex.williamson@redhat.com>
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

I prefer adjacent and not abutting.

> ---
>  hw/virtio/vhost.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 250f886acb..fc9062a89f 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -595,10 +595,15 @@ static void vhost_region_add_section(struct vhost_dev *dev,
>                                          prev_sec->offset_within_address_space,
>                                          prev_sec->offset_within_region);
>              } else {
> -                error_report("%s: Overlapping but not coherent sections "
> -                             "at %"PRIx64,
> -                             __func__, mrs_gpa);
> -                return;
> +                /* abutting regions are fine, but overlapping ones with
> +                 * different blocks/offsets shouldn't happen
> +                 */
> +                if (mrs_gpa != prev_gpa_end + 1) {
> +                    error_report("%s: Overlapping but not coherent sections "
> +                                 "at %"PRIx64,
> +                                 __func__, mrs_gpa);
> +                    return;
> +                }
>              }
>          }
>      }
> -- 
> 2.14.3