diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 58560c044d..a9ebef8a35 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -69,6 +69,7 @@ static void pcibus_reset(BusState *qbus);
 static Property pci_props[] = {
     DEFINE_PROP_PCI_DEVFN("addr", PCIDevice, devfn, -1),
     DEFINE_PROP_STRING("romfile", PCIDevice, romfile),
+    DEFINE_PROP_UINT32("romsize", PCIDevice, romsize, -1),
     DEFINE_PROP_UINT32("rombar",  PCIDevice, rom_bar, 1),
     DEFINE_PROP_BIT("multifunction", PCIDevice, cap_present,
                     QEMU_PCI_CAP_MULTIFUNCTION_BITNR, false),
@@ -2084,6 +2085,11 @@ static void pci_qdev_realize(DeviceState *qdev, Error **errp)
     bool is_default_rom;
     uint16_t class_id;
 
+    if (pci_dev->romsize != -1 && !is_power_of_2(pci_dev->romsize)) {
+        error_setg(errp, "ROM size %u is not a power of two", pci_dev->romsize);
+        return;
+    }
+
     /* initialize cap_present for pci_is_express() and pci_config_size(),
      * Note that hybrid PCIs are not set automatically and need to manage
      * QEMU_PCI_CAP_EXPRESS manually */
@@ -2349,7 +2355,16 @@ static void pci_add_option_rom(PCIDevice *pdev, bool is_default_rom,
         g_free(path);
         return;
     }
-    size = pow2ceil(size);
+    if (pdev->romsize != -1) {
+        if (size > pdev->romsize) {
+            error_setg(errp, "romfile \"%s\" (%u bytes) is too large for ROM size %u",
+                       pdev->romfile, (uint32_t)size, pdev->romsize);
+            g_free(path);
+            return;
+        }
+    } else {
+        pdev->romsize = pow2ceil(size);
+    }
 
     vmsd = qdev_get_vmsd(DEVICE(pdev));
 
@@ -2359,7 +2374,7 @@ static void pci_add_option_rom(PCIDevice *pdev, bool is_default_rom,
         snprintf(name, sizeof(name), "%s.rom", object_get_typename(OBJECT(pdev)));
     }
     pdev->has_rom = true;
-    memory_region_init_rom(&pdev->rom, OBJECT(pdev), name, size, &error_fatal);
+    memory_region_init_rom(&pdev->rom, OBJECT(pdev), name, pdev->romsize, &error_fatal);
     ptr = memory_region_get_ram_ptr(&pdev->rom);
     if (load_image_size(path, ptr, size) < 0) {
         error_setg(errp, "failed to load romfile \"%s\"", pdev->romfile);
diff --git a/hw/xen/xen_pt_load_rom.c b/hw/xen/xen_pt_load_rom.c
index a50a80837e..03422a8a71 100644
--- a/hw/xen/xen_pt_load_rom.c
+++ b/hw/xen/xen_pt_load_rom.c
@@ -53,10 +53,20 @@ void *pci_assign_dev_load_option_rom(PCIDevice *dev,
     }
     fseek(fp, 0, SEEK_SET);
 
+    if (dev->romsize != -1) {
+        if (st.st_size > dev->romsize) {
+            error_report("ROM BAR \"%s\" (%ld bytes) is too large for ROM size %u",
+                         rom_file, (long) st.st_size, dev->romsize);
+            goto close_rom;
+        }
+    } else {
+        dev->romsize = st.st_size;
+    }
+
     snprintf(name, sizeof(name), "%s.rom", object_get_typename(owner));
-    memory_region_init_ram(&dev->rom, owner, name, st.st_size, &error_abort);
+    memory_region_init_ram(&dev->rom, owner, name, dev->romsize, &error_abort);
     ptr = memory_region_get_ram_ptr(&dev->rom);
-    memset(ptr, 0xff, st.st_size);
+    memset(ptr, 0xff, dev->romsize);
 
     if (!fread(ptr, 1, st.st_size, fp)) {
         error_report("pci-assign: Cannot read from host %s", rom_file);
diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
index 66db08462f..1bc231480f 100644
--- a/include/hw/pci/pci.h
+++ b/include/hw/pci/pci.h
@@ -344,6 +344,7 @@ struct PCIDevice {
 
     /* Location of option rom */
     char *romfile;
+    uint32_t romsize;
     bool has_rom;
     MemoryRegion rom;
     uint32_t rom_bar;