diff --git a/hw/block/pc_sysfw.c b/hw/block/pc_sysfw.c
index 0d95c8a9261f2d93fd055e94297a04cd81c2e507..aad8614465bd446f7f9704921436bfdfa26086a0 100644
--- a/hw/block/pc_sysfw.c
+++ b/hw/block/pc_sysfw.c
@@ -194,11 +194,23 @@ static void old_pc_system_rom_init(MemoryRegion *rom_memory)
                                 bios);
 }
 
+/*
+ * Bug-compatible flash vs. ROM selection enabled?
+ * A few older machines enable this.
+ */
+bool pc_sysfw_flash_vs_rom_bug_compatible;
+
 void pc_system_firmware_init(MemoryRegion *rom_memory)
 {
     DriveInfo *pflash_drv;
     PcSysFwDevice *sysfw_dev;
 
+    /*
+     * TODO This device exists only so that users can switch between
+     * use of flash and ROM for the BIOS.  The ability to switch was
+     * created because flash doesn't work with KVM.  Once it does, we
+     * should drop this device for new machine types.
+     */
     sysfw_dev = (PcSysFwDevice*) qdev_create(NULL, "pc-sysfw");
 
     qdev_init_nofail(DEVICE(sysfw_dev));
@@ -212,7 +224,11 @@ void pc_system_firmware_init(MemoryRegion *rom_memory)
 
     /* Currently KVM cannot execute from device memory.
        Use old rom based firmware initialization for KVM. */
-    if (kvm_enabled()) {
+    /*
+     * This is a Bad Idea, because it makes enabling/disabling KVM
+     * guest-visible.  Do it only in bug-compatibility mode.
+     */
+    if (pc_sysfw_flash_vs_rom_bug_compatible && kvm_enabled()) {
         if (pflash_drv != NULL) {
             fprintf(stderr, "qemu: pflash cannot be used with kvm enabled\n");
             exit(1);
@@ -239,7 +255,7 @@ void pc_system_firmware_init(MemoryRegion *rom_memory)
 }
 
 static Property pcsysfw_properties[] = {
-    DEFINE_PROP_UINT8("rom_only", PcSysFwDevice, rom_only, 0),
+    DEFINE_PROP_UINT8("rom_only", PcSysFwDevice, rom_only, 1),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index 13e1d50fc0c24bcc7ea07bfd70b0e42b30edc275..89b4cb46357e89860e833a671c15433705908856 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -235,9 +235,16 @@ static void pc_init_pci(QEMUMachineInitArgs *args)
              initrd_filename, cpu_model, 1, 1);
 }
 
+static void pc_init_pci_1_4(QEMUMachineInitArgs *args)
+{
+    pc_sysfw_flash_vs_rom_bug_compatible = true;
+    pc_init_pci(args);
+}
+
 static void pc_init_pci_1_3(QEMUMachineInitArgs *args)
 {
     enable_compat_apic_id_mode();
+    pc_sysfw_flash_vs_rom_bug_compatible = true;
     pc_init_pci(args);
 }
 
@@ -246,6 +253,7 @@ static void pc_init_pci_1_2(QEMUMachineInitArgs *args)
 {
     disable_kvm_pv_eoi();
     enable_compat_apic_id_mode();
+    pc_sysfw_flash_vs_rom_bug_compatible = true;
     pc_init_pci(args);
 }
 
@@ -318,7 +326,7 @@ static QEMUMachine pc_i440fx_machine_v1_5 = {
 static QEMUMachine pc_i440fx_machine_v1_4 = {
     .name = "pc-i440fx-1.4",
     .desc = "Standard PC (i440FX + PIIX, 1996)",
-    .init = pc_init_pci,
+    .init = pc_init_pci_1_4,
     .max_cpus = 255,
     .compat_props = (GlobalProperty[]) {
         PC_COMPAT_1_4,
diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
index e5f417ee085965e2880134bb155b7c26b7a69d90..f16089387c4dfefc52f70646e10d0d6982620193 100644
--- a/hw/i386/pc_q35.c
+++ b/hw/i386/pc_q35.c
@@ -196,6 +196,12 @@ static void pc_q35_init(QEMUMachineInitArgs *args)
     }
 }
 
+static void pc_q35_init_1_4(QEMUMachineInitArgs *args)
+{
+    pc_sysfw_flash_vs_rom_bug_compatible = true;
+    pc_q35_init(args);
+}
+
 static QEMUMachine pc_q35_machine_v1_5 = {
     .name = "pc-q35-1.5",
     .alias = "q35",
@@ -208,7 +214,7 @@ static QEMUMachine pc_q35_machine_v1_5 = {
 static QEMUMachine pc_q35_machine_v1_4 = {
     .name = "pc-q35-1.4",
     .desc = "Standard PC (Q35 + ICH9, 2009)",
-    .init = pc_q35_init,
+    .init = pc_q35_init_1_4,
     .max_cpus = 255,
     .compat_props = (GlobalProperty[]) {
         PC_COMPAT_1_4,
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index 9bcc8193b7aced0e8f3902a482c2067a72d45394..14b504c74dace525fc876291f89fd92593d01362 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -168,6 +168,7 @@ static inline bool isa_ne2000_init(ISABus *bus, int base, int irq, NICInfo *nd)
 }
 
 /* pc_sysfw.c */
+extern bool pc_sysfw_flash_vs_rom_bug_compatible;
 void pc_system_firmware_init(MemoryRegion *rom_memory);
 
 /* e820 types */
@@ -233,6 +234,10 @@ int e820_add_entry(uint64_t, uint64_t, uint32_t);
             .driver   = "virtio-net-pci",\
             .property = "romfile",\
             .value    = "pxe-virtio.rom",\
+        },{\
+            .driver   = "pc-sysfw",\
+            .property = "rom_only",\
+            .value    = stringify(0),\
         }
 
 #endif