[Qemu-devel] [PATCH v2 03/17] memory: add ref/unref calls

[Paolo Bonzini <pbonzini@redhat.com>]

Add ref/unref calls at the following places:

- places where memory regions are stashed by a listener and
  used outside the BQL (including in Xen or KVM).

- memory_region_find callsites

- creation of aliases and containers (only the aliased/contained
  region gets a reference to avoid loops)

- around calls to del_subregion/add_subregion, where the region
  could disappear after the first call

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 exec.c                                |  6 +++++-
 hw/core/loader.c                      |  1 +
 hw/display/exynos4210_fimd.c          |  6 ++++++
 hw/display/framebuffer.c              | 12 +++++++-----
 hw/i386/kvmvapic.c                    |  1 +
 hw/misc/vfio.c                        |  2 ++
 hw/virtio/dataplane/hostmem.c         |  7 +++++++
 hw/virtio/vhost.c                     |  2 ++
 hw/virtio/virtio-balloon.c            |  1 +
 hw/xen/xen_pt.c                       |  4 ++++
 include/hw/virtio/dataplane/hostmem.h |  1 +
 kvm-all.c                             |  2 ++
 memory.c                              | 20 ++++++++++++++++++++
 target-arm/kvm.c                      |  2 ++
 target-sparc/mmu_helper.c             |  1 +
 xen-all.c                             |  2 ++
 16 files changed, 64 insertions(+), 6 deletions(-)

diff --git a/exec.c b/exec.c
index 8909478..ba50e8d 100644
--- a/exec.c
+++ b/exec.c
@@ -815,12 +815,16 @@ static uint16_t phys_section_add(MemoryRegionSection *section)
                                 phys_sections_nb_alloc);
     }
     phys_sections[phys_sections_nb] = *section;
+    memory_region_ref(section->mr);
     return phys_sections_nb++;
 }
 
 static void phys_sections_clear(void)
 {
-    phys_sections_nb = 0;
+    while (phys_sections_nb > 0) {
+        MemoryRegionSection *section = &phys_sections[--phys_sections_nb];
+        memory_region_unref(section->mr);
+    }
 }
 
 static void register_subpage(AddressSpaceDispatch *d, MemoryRegionSection *section)
diff --git a/hw/core/loader.c b/hw/core/loader.c
index 3a60cbe..44d8714 100644
--- a/hw/core/loader.c
+++ b/hw/core/loader.c
@@ -727,6 +727,7 @@ int rom_load_all(void)
         addr += rom->romsize;
         section = memory_region_find(get_system_memory(), rom->addr, 1);
         rom->isrom = int128_nz(section.size) && memory_region_is_rom(section.mr);
+        memory_region_unref(section.mr);
     }
     qemu_register_reset(rom_reset, NULL);
     roms_loaded = 1;
diff --git a/hw/display/exynos4210_fimd.c b/hw/display/exynos4210_fimd.c
index 0da00a9..f44c4a6 100644
--- a/hw/display/exynos4210_fimd.c
+++ b/hw/display/exynos4210_fimd.c
@@ -1126,6 +1126,11 @@ static void fimd_update_memory_section(Exynos4210fimdState *s, unsigned win)
     /* Total number of bytes of virtual screen used by current window */
     w->fb_len = fb_mapped_len = (w->virtpage_width + w->virtpage_offsize) *
             (w->rightbot_y - w->lefttop_y + 1);
+
+    /* TODO: add .exit and unref the region there.  Not needed yet since sysbus
+     * does not support hot-unplug.
+     */
+    memory_region_unref(w->mem_section.mr);
     w->mem_section = memory_region_find(sysbus_address_space(&s->busdev),
             fb_start_addr, w->fb_len);
     assert(w->mem_section.mr);
@@ -1154,6 +1159,7 @@ static void fimd_update_memory_section(Exynos4210fimdState *s, unsigned win)
     return;
 
 error_return:
+    memory_region_unref(w->mem_section.mr);
     w->mem_section.mr = NULL;
     w->mem_section.size = int128_zero();
     w->host_fb_addr = NULL;
diff --git a/hw/display/framebuffer.c b/hw/display/framebuffer.c
index 49c9e59..4546e42 100644
--- a/hw/display/framebuffer.c
+++ b/hw/display/framebuffer.c
@@ -54,11 +54,11 @@ void framebuffer_update_display(
     src_len = src_width * rows;
 
     mem_section = memory_region_find(address_space, base, src_len);
+    mem = mem_section.mr;
     if (int128_get64(mem_section.size) != src_len ||
             !memory_region_is_ram(mem_section.mr)) {
-        return;
+        goto out;
     }
-    mem = mem_section.mr;
     assert(mem);
     assert(mem_section.offset_within_address_space == base);
 
@@ -68,10 +68,10 @@ void framebuffer_update_display(
        but it's not really worth it as dirty flag tracking will probably
        already have failed above.  */
     if (!src_base)
-        return;
+        goto out;
     if (src_len != src_width * rows) {
         cpu_physical_memory_unmap(src_base, src_len, 0, 0);
-        return;
+        goto out;
     }
     src = src_base;
     dest = surface_data(ds);
@@ -102,10 +102,12 @@ void framebuffer_update_display(
     }
     cpu_physical_memory_unmap(src_base, src_len, 0, 0);
     if (first < 0) {
-        return;
+        goto out;
     }
     memory_region_reset_dirty(mem, mem_section.offset_within_region, src_len,
                               DIRTY_MEMORY_VGA);
     *first_row = first;
     *last_row = last;
+out:
+    memory_region_unref(mem);
 }
diff --git a/hw/i386/kvmvapic.c b/hw/i386/kvmvapic.c
index 655483b..e375c1c 100644
--- a/hw/i386/kvmvapic.c
+++ b/hw/i386/kvmvapic.c
@@ -605,6 +605,7 @@ static void vapic_map_rom_writable(VAPICROMState *s)
                              rom_size);
     memory_region_add_subregion_overlap(as, rom_paddr, &s->rom, 1000);
     s->rom_mapped_writable = true;
+    memory_region_unref(section.mr);
 }
 
 static int vapic_prepare(VAPICROMState *s)
diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c
index 52fb036..a1f5803 100644
--- a/hw/misc/vfio.c
+++ b/hw/misc/vfio.c
@@ -1969,6 +1969,7 @@ static void vfio_listener_region_add(MemoryListener *listener,
     DPRINTF("region_add %"HWADDR_PRIx" - %"HWADDR_PRIx" [%p]\n",
             iova, end - 1, vaddr);
 
+    memory_region_ref(section->mr);
     ret = vfio_dma_map(container, iova, end - iova, vaddr, section->readonly);
     if (ret) {
         error_report("vfio_dma_map(%p, 0x%"HWADDR_PRIx", "
@@ -2010,6 +2011,7 @@ static void vfio_listener_region_del(MemoryListener *listener,
             iova, end - 1);
 
     ret = vfio_dma_unmap(container, iova, end - iova);
+    memory_region_unref(section->mr);
     if (ret) {
         error_report("vfio_dma_unmap(%p, 0x%"HWADDR_PRIx", "
                      "0x%"HWADDR_PRIx") = %d (%m)",
diff --git a/hw/virtio/dataplane/hostmem.c b/hw/virtio/dataplane/hostmem.c
index 7e46723..901d98b 100644
--- a/hw/virtio/dataplane/hostmem.c
+++ b/hw/virtio/dataplane/hostmem.c
@@ -64,8 +64,12 @@ out:
 static void hostmem_listener_commit(MemoryListener *listener)
 {
     HostMem *hostmem = container_of(listener, HostMem, listener);
+    int i;
 
     qemu_mutex_lock(&hostmem->current_regions_lock);
+    for (i = 0; i < hostmem->num_current_regions; i++) {
+        memory_region_unref(hostmem->current_regions[i].mr);
+    }
     g_free(hostmem->current_regions);
     hostmem->current_regions = hostmem->new_regions;
     hostmem->num_current_regions = hostmem->num_new_regions;
@@ -92,8 +96,11 @@ static void hostmem_append_new_region(HostMem *hostmem,
         .guest_addr = section->offset_within_address_space,
         .size = int128_get64(section->size),
         .readonly = section->readonly,
+        .mr = section->mr,
     };
     hostmem->num_new_regions++;
+
+    memory_region_ref(section->mr);
 }
 
 static void hostmem_listener_append_region(MemoryListener *listener,
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index baf84ea..96ab625 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -497,6 +497,7 @@ static void vhost_region_add(MemoryListener *listener,
     dev->mem_sections = g_renew(MemoryRegionSection, dev->mem_sections,
                                 dev->n_mem_sections);
     dev->mem_sections[dev->n_mem_sections - 1] = *section;
+    memory_region_ref(section->mr);
     vhost_set_memory(listener, section, true);
 }
 
@@ -512,6 +513,7 @@ static void vhost_region_del(MemoryListener *listener,
     }
 
     vhost_set_memory(listener, section, false);
+    memory_region_unref(section->mr);
     for (i = 0; i < dev->n_mem_sections; ++i) {
         if (dev->mem_sections[i].offset_within_address_space
             == section->offset_within_address_space) {
diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index a27051c..3fa72a9 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -205,6 +205,7 @@ static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq)
             addr = section.offset_within_region;
             balloon_page(memory_region_get_ram_ptr(section.mr) + addr,
                          !!(vq == s->dvq));
+            memory_region_unref(section.mr);
         }
 
         virtqueue_push(vq, &elem, offset);
diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
index c199818..be1fd52 100644
--- a/hw/xen/xen_pt.c
+++ b/hw/xen/xen_pt.c
@@ -606,6 +606,7 @@ static void xen_pt_region_add(MemoryListener *l, MemoryRegionSection *sec)
     XenPCIPassthroughState *s = container_of(l, XenPCIPassthroughState,
                                              memory_listener);
 
+    memory_region_ref(sec->mr);
     xen_pt_region_update(s, sec, true);
 }
 
@@ -615,6 +616,7 @@ static void xen_pt_region_del(MemoryListener *l, MemoryRegionSection *sec)
                                              memory_listener);
 
     xen_pt_region_update(s, sec, false);
+    memory_region_unref(sec->mr);
 }
 
 static void xen_pt_io_region_add(MemoryListener *l, MemoryRegionSection *sec)
@@ -622,6 +624,7 @@ static void xen_pt_io_region_add(MemoryListener *l, MemoryRegionSection *sec)
     XenPCIPassthroughState *s = container_of(l, XenPCIPassthroughState,
                                              io_listener);
 
+    memory_region_ref(sec->mr);
     xen_pt_region_update(s, sec, true);
 }
 
@@ -631,6 +634,7 @@ static void xen_pt_io_region_del(MemoryListener *l, MemoryRegionSection *sec)
                                              io_listener);
 
     xen_pt_region_update(s, sec, false);
+    memory_region_unref(sec->mr);
 }
 
 static const MemoryListener xen_pt_memory_listener = {
diff --git a/include/hw/virtio/dataplane/hostmem.h b/include/hw/virtio/dataplane/hostmem.h
index b2cf093..2810f4b 100644
--- a/include/hw/virtio/dataplane/hostmem.h
+++ b/include/hw/virtio/dataplane/hostmem.h
@@ -18,6 +18,7 @@
 #include "qemu/thread.h"
 
 typedef struct {
+    MemoryRegion *mr;
     void *host_addr;
     hwaddr guest_addr;
     uint64_t size;
diff --git a/kvm-all.c b/kvm-all.c
index e6b262f..91aa7ff 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -788,6 +788,7 @@ static void kvm_set_phys_mem(MemoryRegionSection *section, bool add)
 static void kvm_region_add(MemoryListener *listener,
                            MemoryRegionSection *section)
 {
+    memory_region_ref(section->mr);
     kvm_set_phys_mem(section, true);
 }
 
@@ -795,6 +796,7 @@ static void kvm_region_del(MemoryListener *listener,
                            MemoryRegionSection *section)
 {
     kvm_set_phys_mem(section, false);
+    memory_region_unref(section->mr);
 }
 
 static void kvm_log_sync(MemoryListener *listener,
diff --git a/memory.c b/memory.c
index a136a77..cfce42b 100644
--- a/memory.c
+++ b/memory.c
@@ -147,6 +147,7 @@ static bool memory_listener_match(MemoryListener *listener,
         }                                                               \
     } while (0)
 
+/* No need to ref/unref .mr, the FlatRange keeps it alive.  */
 #define MEMORY_LISTENER_UPDATE_REGION(fr, as, dir, callback)            \
     MEMORY_LISTENER_CALL(callback, dir, (&(MemoryRegionSection) {       \
         .mr = (fr)->mr,                                                 \
@@ -262,11 +263,17 @@ static void flatview_insert(FlatView *view, unsigned pos, FlatRange *range)
     memmove(view->ranges + pos + 1, view->ranges + pos,
             (view->nr - pos) * sizeof(FlatRange));
     view->ranges[pos] = *range;
+    memory_region_ref(range->mr);
     ++view->nr;
 }
 
 static void flatview_destroy(FlatView *view)
 {
+    int i;
+
+    for (i = 0; i < view->nr; i++) {
+        memory_region_unref(view->ranges[i].mr);
+    }
     g_free(view->ranges);
 }
 
@@ -796,6 +803,11 @@ static void memory_region_destructor_ram(MemoryRegion *mr)
     qemu_ram_free(mr->ram_addr);
 }
 
+static void memory_region_destructor_alias(MemoryRegion *mr)
+{
+    memory_region_unref(mr->alias);
+}
+
 static void memory_region_destructor_ram_from_ptr(MemoryRegion *mr)
 {
     qemu_ram_free_from_ptr(mr->ram_addr);
@@ -1043,6 +1055,8 @@ void memory_region_init_alias(MemoryRegion *mr,
                               uint64_t size)
 {
     memory_region_init(mr, name, size);
+    memory_region_ref(orig);
+    mr->destructor = memory_region_destructor_alias;
     mr->alias = orig;
     mr->alias_offset = offset;
 }
@@ -1457,6 +1471,7 @@ static void memory_region_add_subregion_common(MemoryRegion *mr,
     memory_region_transaction_begin();
 
     assert(!subregion->parent);
+    memory_region_ref(subregion);
     subregion->parent = mr;
     subregion->addr = offset;
     QTAILQ_FOREACH(other, &mr->subregions, subregions_link) {
@@ -1519,6 +1534,7 @@ void memory_region_del_subregion(MemoryRegion *mr,
     assert(subregion->parent == mr);
     subregion->parent = NULL;
     QTAILQ_REMOVE(&mr->subregions, subregion, subregions_link);
+    memory_region_unref(subregion);
     memory_region_update_pending |= mr->enabled && subregion->enabled;
     memory_region_transaction_commit();
 }
@@ -1546,12 +1562,14 @@ void memory_region_set_address(MemoryRegion *mr, hwaddr addr)
     }
 
     memory_region_transaction_begin();
+    memory_region_ref(mr);
     memory_region_del_subregion(parent, mr);
     if (may_overlap) {
         memory_region_add_subregion_overlap(parent, addr, mr, priority);
     } else {
         memory_region_add_subregion(parent, addr, mr);
     }
+    memory_region_unref(mr);
     memory_region_transaction_commit();
 }
 
@@ -1629,6 +1647,8 @@ MemoryRegionSection memory_region_find(MemoryRegion *mr,
     ret.size = range.size;
     ret.offset_within_address_space = int128_get64(range.start);
     ret.readonly = fr->readonly;
+    memory_region_ref(ret.mr);
+
     return ret;
 }
 
diff --git a/target-arm/kvm.c b/target-arm/kvm.c
index b7bdc03..b9051a4 100644
--- a/target-arm/kvm.c
+++ b/target-arm/kvm.c
@@ -127,6 +127,7 @@ static void kvm_arm_machine_init_done(Notifier *notifier, void *data)
                 abort();
             }
         }
+        memory_region_unref(kd->mr);
         g_free(kd);
     }
 }
@@ -152,6 +153,7 @@ void kvm_arm_register_device(MemoryRegion *mr, uint64_t devid)
     kd->kda.id = devid;
     kd->kda.addr = -1;
     QSLIST_INSERT_HEAD(&kvm_devices_head, kd, entries);
+    memory_region_ref(kd->mr);
 }
 
 typedef struct Reg {
diff --git a/target-sparc/mmu_helper.c b/target-sparc/mmu_helper.c
index 3983c96..740cbe8 100644
--- a/target-sparc/mmu_helper.c
+++ b/target-sparc/mmu_helper.c
@@ -845,6 +845,7 @@ hwaddr cpu_get_phys_page_debug(CPUSPARCState *env, target_ulong addr)
         }
     }
     section = memory_region_find(get_system_memory(), phys_addr, 1);
+    memory_region_unref(section.mr);
     if (!int128_nz(section.size)) {
         return -1;
     }
diff --git a/xen-all.c b/xen-all.c
index cd520b1..764741a 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -459,6 +459,7 @@ static void xen_set_memory(struct MemoryListener *listener,
 static void xen_region_add(MemoryListener *listener,
                            MemoryRegionSection *section)
 {
+    memory_region_ref(section->mr);
     xen_set_memory(listener, section, true);
 }
 
@@ -466,6 +467,7 @@ static void xen_region_del(MemoryListener *listener,
                            MemoryRegionSection *section)
 {
     xen_set_memory(listener, section, false);
+    memory_region_unref(section->mr);
 }
 
 static void xen_sync_dirty_bitmap(XenIOState *state,
-- 
1.8.1.4