From 34644299c4e930a16b7e0a7725f69b7b83ca600e Mon Sep 17 00:00:00 2001
From: David Gibson <dgibson@redhat.com>
Date: Thu, 16 Nov 2017 03:07:31 +0100
Subject: [PATCH 27/30] memory: seek FlatView sharing candidates among children
 subregions

RH-Author: David Gibson <dgibson@redhat.com>
Message-id: <20171116030732.8560-22-dgibson@redhat.com>
Patchwork-id: 77708
O-Subject: [PATCH 21/22] memory: seek FlatView sharing candidates among children subregions
Bugzilla: 1481593
RH-Acked-by: Thomas Huth <thuth@redhat.com>
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com>
RH-Acked-by: Laurent Vivier <lvivier@redhat.com>

From: Paolo Bonzini <pbonzini@redhat.com>

A container can be used instead of an alias to allow switching between
multiple subregions.  In this case we cannot directly share the
subregions (since they only belong to a single parent), but if the
subregions are aliases we can in turn walk those.

This is not enough to remove all source of quadratic FlatView creation,
but it enables sharing of the PCI bus master FlatViews (and their
AddressSpaceDispatch structures) across all PCI devices.  For 112
virtio-net-pci devices, boot time is reduced from 25 to 10 seconds and
memory consumption from 1.4 to 1 G.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit e673ba9af9bf8fd8e0f44025ac738b8285b3ed27)

Signed-off-by: David Gibson <dgibson@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 memory.c | 40 ++++++++++++++++++++++++++++++++++------
 1 file changed, 34 insertions(+), 6 deletions(-)

diff --git a/memory.c b/memory.c
index 8733efc..38eabe7 100644
--- a/memory.c
+++ b/memory.c
@@ -733,12 +733,40 @@ static void render_memory_region(FlatView *view,
 
 static MemoryRegion *memory_region_get_flatview_root(MemoryRegion *mr)
 {
-    while (mr->alias && !mr->alias_offset &&
-           int128_ge(mr->size, mr->alias->size)) {
-        /* The alias is included in its entirety.  Use it as
-         * the "real" root, so that we can share more FlatViews.
-         */
-        mr = mr->alias;
+    while (mr->enabled) {
+        if (mr->alias) {
+            if (!mr->alias_offset && int128_ge(mr->size, mr->alias->size)) {
+                /* The alias is included in its entirety.  Use it as
+                 * the "real" root, so that we can share more FlatViews.
+                 */
+                mr = mr->alias;
+                continue;
+            }
+        } else if (!mr->terminates) {
+            unsigned int found = 0;
+            MemoryRegion *child, *next = NULL;
+            QTAILQ_FOREACH(child, &mr->subregions, subregions_link) {
+                if (child->enabled) {
+                    if (++found > 1) {
+                        next = NULL;
+                        break;
+                    }
+                    if (!child->addr && int128_ge(mr->size, child->size)) {
+                        /* A child is included in its entirety.  If it's the only
+                         * enabled one, use it in the hope of finding an alias down the
+                         * way. This will also let us share FlatViews.
+                         */
+                        next = child;
+                    }
+                }
+            }
+            if (next) {
+                mr = next;
+                continue;
+            }
+        }
+
+        break;
     }
 
     return mr;
-- 
1.8.3.1