virtio-pci: Replace modern_as with direct access to modern_bar

The modern bar is accessed now via yet another address space created just
for that purpose and it does not really need FlatView and dispatch tree
as it has a single memory region so it is just a waste of memory. Things
get even worse when there are dozens or hundreds of virtio-pci devices -
since these address spaces are global, changing any of them triggers
rebuilding all address spaces.

This replaces indirect accesses to the modern BAR with a simple lookup
and direct calls to memory_region_dispatch_read/write.

This is expected to save lots of memory at boot time after applying:
[Qemu-devel] [PULL 00/32] Misc changes for 2017-09-22

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 10 insertions, 7 deletions

diff --git a/hw/virtio/virtio-pci.h b/hw/virtio/virtio-pci.h
index 69f5959623..12d3a90686 100644
--- a/hw/virtio/virtio-pci.h
+++ b/hw/virtio/virtio-pci.h
@@ -155,15 +155,18 @@ typedef struct VirtIOPCIQueue {
 struct VirtIOPCIProxy {
     PCIDevice pci_dev;
     MemoryRegion bar;
-    VirtIOPCIRegion common;
-    VirtIOPCIRegion isr;
-    VirtIOPCIRegion device;
-    VirtIOPCIRegion notify;
-    VirtIOPCIRegion notify_pio;
+    union {
+        struct {
+            VirtIOPCIRegion common;
+            VirtIOPCIRegion isr;
+            VirtIOPCIRegion device;
+            VirtIOPCIRegion notify;
+            VirtIOPCIRegion notify_pio;
+        };
+        VirtIOPCIRegion regs[5];
+    };
     MemoryRegion modern_bar;
     MemoryRegion io_bar;
-    MemoryRegion modern_cfg;
-    AddressSpace modern_as;
     uint32_t legacy_io_bar_idx;
     uint32_t msix_bar_idx;
     uint32_t modern_io_bar_idx;