The pci-testdev device allows for an optional BAR. We have
historically used this without backing to test that systems and OSes
can accomodate large PCI BARs. However to help test p2pdma operations
it is helpful to add an option to back this BAR with host memory.

We add a membar-backed boolean parameter and when set to true or on we
do a host RAM backing. The default is false which ensures backward
compatability.

Signed-off-by: Stephen Bates <sbates@raithlin.com>
---
 hw/misc/pci-testdev.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/hw/misc/pci-testdev.c b/hw/misc/pci-testdev.c
index f6718a7c37..da9126a8a7 100644
--- a/hw/misc/pci-testdev.c
+++ b/hw/misc/pci-testdev.c
@@ -90,6 +90,7 @@ struct PCITestDevState {
     int current;
 
     uint64_t membar_size;
+    bool membar_backed;
     MemoryRegion membar;
 };
 
@@ -258,8 +259,14 @@ static void pci_testdev_realize(PCIDevice *pci_dev, Error **errp)
     pci_register_bar(pci_dev, 1, PCI_BASE_ADDRESS_SPACE_IO, &d->portio);
 
     if (d->membar_size) {
-        memory_region_init(&d->membar, OBJECT(d), "pci-testdev-membar",
-                           d->membar_size);
+        if (d->membar_backed)
+            memory_region_init_ram(&d->membar, OBJECT(d),
+                                   "pci-testdev-membar-backed",
+                                   d->membar_size, NULL);
+        else
+            memory_region_init(&d->membar, OBJECT(d),
+                               "pci-testdev-membar",
+                               d->membar_size);
         pci_register_bar(pci_dev, 2,
                          PCI_BASE_ADDRESS_SPACE_MEMORY |
                          PCI_BASE_ADDRESS_MEM_PREFETCH |
@@ -321,6 +328,8 @@ static void qdev_pci_testdev_reset(DeviceState *dev)
 
 static const Property pci_testdev_properties[] = {
     DEFINE_PROP_SIZE("membar", PCITestDevState, membar_size, 0),
+    DEFINE_PROP_BOOL("membar-backed", PCITestDevState, membar_backed, false),
+    DEFINE_PROP_END_OF_LIST(),
 };
 
 static void pci_testdev_class_init(ObjectClass *klass, void *data)
-- 
2.43.0


-- 

Cheers

Stephen Bates, PhD.