From: "Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>
Date: Fri, 23 Mar 2018 12:46:37 +0000
Message-Id: <20180323124637.11220-1-dgilbert@redhat.com>
Subject: [Qemu-devel] [PATCH] vhost: Allow abutting regions
To: qemu-devel@nongnu.org, mst@redhat.com, alex.williamson@redhat.com

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