[Qemu-devel] [PATCH for-1.5] Revert "pc: Kill the "use flash device for BIOS unless KVM" misfeature"

[Paolo Bonzini <pbonzini@redhat.com>]

This reverts commit 9953f8822cc316eec9962f0a2858c3439a80adec.
While Markus's analysis is entirely correct, there are 1.6 patches
that fix the bug for real and without requiring machine type hacks.
Let's think of the children who will have to read this code, and
avoid a complicated mess of semantics that differ between <1.5,
1.5, and >1.5.

Conflicts:
	hw/i386/pc_piix.c
	hw/i386/pc_q35.c
	include/hw/i386/pc.h

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/block/pc_sysfw.c  | 8 ++++----
 hw/i386/pc_piix.c    | 3 ---
 hw/i386/pc_q35.c     | 1 -
 include/hw/i386/pc.h | 5 -----
 4 files changed, 4 insertions(+), 13 deletions(-)

diff --git a/hw/block/pc_sysfw.c b/hw/block/pc_sysfw.c
index aad8614..4f17668 100644
--- a/hw/block/pc_sysfw.c
+++ b/hw/block/pc_sysfw.c
@@ -209,7 +209,7 @@ void pc_system_firmware_init(MemoryRegion *rom_memory)
      * 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.
+     * should drop this device.
      */
     sysfw_dev = (PcSysFwDevice*) qdev_create(NULL, "pc-sysfw");
 
@@ -226,9 +226,9 @@ void pc_system_firmware_init(MemoryRegion *rom_memory)
        Use old rom based firmware initialization for KVM. */
     /*
      * This is a Bad Idea, because it makes enabling/disabling KVM
-     * guest-visible.  Do it only in bug-compatibility mode.
+     * guest-visible.  Let's fix it for real in QEMU 1.6.
      */
-    if (pc_sysfw_flash_vs_rom_bug_compatible && kvm_enabled()) {
+    if (kvm_enabled()) {
         if (pflash_drv != NULL) {
             fprintf(stderr, "qemu: pflash cannot be used with kvm enabled\n");
             exit(1);
@@ -255,7 +255,7 @@ void pc_system_firmware_init(MemoryRegion *rom_memory)
 }
 
 static Property pcsysfw_properties[] = {
-    DEFINE_PROP_UINT8("rom_only", PcSysFwDevice, rom_only, 1),
+    DEFINE_PROP_UINT8("rom_only", PcSysFwDevice, rom_only, 0),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index f7c80ad..43ab480 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -248,7 +248,6 @@ static void pc_init_pci(QEMUMachineInitArgs *args)
 
 static void pc_init_pci_1_4(QEMUMachineInitArgs *args)
 {
-    pc_sysfw_flash_vs_rom_bug_compatible = true;
     has_pvpanic = false;
     x86_cpu_compat_set_features("n270", FEAT_1_ECX, 0, CPUID_EXT_MOVBE);
     pc_init_pci(args);
@@ -257,7 +256,6 @@ static void pc_init_pci_1_4(QEMUMachineInitArgs *args)
 static void pc_init_pci_1_3(QEMUMachineInitArgs *args)
 {
     enable_compat_apic_id_mode();
-    pc_sysfw_flash_vs_rom_bug_compatible = true;
     has_pvpanic = false;
     pc_init_pci(args);
 }
@@ -267,7 +265,6 @@ 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;
     has_pvpanic = false;
     pc_init_pci(args);
 }
diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
index 4160e2b..dd95921 100644
--- a/hw/i386/pc_q35.c
+++ b/hw/i386/pc_q35.c
@@ -210,7 +210,6 @@ static void pc_q35_init(QEMUMachineInitArgs *args)
 
 static void pc_q35_init_1_4(QEMUMachineInitArgs *args)
 {
-    pc_sysfw_flash_vs_rom_bug_compatible = true;
     has_pvpanic = false;
     x86_cpu_compat_set_features("n270", FEAT_1_ECX, 0, CPUID_EXT_MOVBE);
     pc_q35_init(args);
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index 417afe4..2bd7090 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -169,7 +169,6 @@ 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);
 
 /* pvpanic.c */
@@ -239,10 +238,6 @@ int e820_add_entry(uint64_t, uint64_t, uint32_t);
             .property = "romfile",\
             .value    = "pxe-virtio.rom",\
         },{\
-            .driver   = "pc-sysfw",\
-            .property = "rom_only",\
-            .value    = stringify(0),\
-        },{\
             .driver   = "486-" TYPE_X86_CPU,\
             .property = "model",\
             .value    = stringify(0),\
-- 
1.8.1.4