[Qemu-devel] [PATCH 30/38] pcie: do not recreate mmcfg I/O region, use an alias instead

[Paolo Bonzini <pbonzini@redhat.com>]

The MMIO regions should not be destroyed and recreated on the fly,
because they might have I/O in progress.  Instead, create an area that
is as large as possible, and then map a window of it into system memory.
This is safe because containers and aliases are never the destination
of I/O, and can be safely deleted at any time.  It is also similar to
how PAM maps windows of system RAM.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/pci/pcie_host.c         | 23 +++++++++++++++++------
 include/hw/pci/pcie_host.h |  1 +
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/hw/pci/pcie_host.c b/hw/pci/pcie_host.c
index b70e5ad..bb676a9 100644
--- a/hw/pci/pcie_host.c
+++ b/hw/pci/pcie_host.c
@@ -110,19 +110,26 @@ static const MemoryRegionOps pcie_mmcfg_ops = {
 int pcie_host_init(PCIExpressHost *e)
 {
     e->base_addr = PCIE_BASE_ADDR_UNMAPPED;
-
+    memory_region_init_io(&e->mmio, OBJECT(e), &pcie_mmcfg_ops, e, "pcie-mmcfg-mmio",
+                          PCIE_MMCFG_SIZE_MAX);
     return 0;
 }
 
 void pcie_host_mmcfg_unmap(PCIExpressHost *e)
 {
     if (e->base_addr != PCIE_BASE_ADDR_UNMAPPED) {
-        memory_region_del_subregion(get_system_memory(), &e->mmio);
-        memory_region_destroy(&e->mmio);
+        memory_region_del_subregion(get_system_memory(), &e->mapped_mmio);
+        memory_region_destroy(&e->mapped_mmio);
         e->base_addr = PCIE_BASE_ADDR_UNMAPPED;
     }
 }
 
+static void pcie_host_instance_finalize(Object *obj)
+{
+    PCIExpressHost *e = PCIE_HOST_BRIDGE(obj);
+    memory_region_destroy(&e->mmio);
+}
+
 void pcie_host_mmcfg_map(PCIExpressHost *e, hwaddr addr,
                          uint32_t size)
 {
@@ -130,10 +137,13 @@ void pcie_host_mmcfg_map(PCIExpressHost *e, hwaddr addr,
     assert(size >= PCIE_MMCFG_SIZE_MIN);
     assert(size <= PCIE_MMCFG_SIZE_MAX);
     e->size = size;
-    memory_region_init_io(&e->mmio, OBJECT(e), &pcie_mmcfg_ops, e,
-                          "pcie-mmcfg", e->size);
     e->base_addr = addr;
-    memory_region_add_subregion(get_system_memory(), e->base_addr, &e->mmio);
+
+    memory_region_init_alias(&e->mapped_mmio, OBJECT(e),
+                             "pcie-mmcfg", &e->mmio,
+                             0, e->size);
+
+    memory_region_add_subregion(get_system_memory(), e->base_addr, &e->mapped_mmio);
 }
 
 void pcie_host_mmcfg_update(PCIExpressHost *e,
@@ -152,6 +162,7 @@ static const TypeInfo pcie_host_type_info = {
     .parent = TYPE_PCI_HOST_BRIDGE,
     .abstract = true,
     .instance_size = sizeof(PCIExpressHost),
+    .instance_finalize = pcie_host_instance_finalize,
 };
 
 static void pcie_host_register_types(void)
diff --git a/include/hw/pci/pcie_host.h b/include/hw/pci/pcie_host.h
index 1228e36..1656bde 100644
--- a/include/hw/pci/pcie_host.h
+++ b/include/hw/pci/pcie_host.h
@@ -41,6 +41,7 @@ struct PCIExpressHost {
 
     /* MMCONFIG mmio area */
     MemoryRegion mmio;
+    MemoryRegion mapped_mmio;
 };
 
 int pcie_host_init(PCIExpressHost *e);
-- 
1.8.3.1