Re: [Qemu-devel] [PATCH v3 1/2] Add machine type pc-1.0-qemu-kvm for live migrate compatibility with qemu-kvm

["Michael S. Tsirkin" <mst@redhat.com>]

On Sun, Sep 21, 2014 at 03:38:58PM +0100, Alex Bligh wrote:
> Add a machine type pc-1.0-qemu-kvm for live migrate compatibility
> with qemu-kvm version 1.0.
> 
> Signed-off-by: Alex Bligh <alex@alex.org.uk>
> ---
>  hw/acpi/piix4.c         |   47 +++++++++++++++++++++++++++++++++++++++++++++--
>  hw/i386/pc_piix.c       |   30 ++++++++++++++++++++++++++++++
>  hw/timer/i8254_common.c |   10 +++++++++-
>  3 files changed, 84 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/acpi/piix4.c b/hw/acpi/piix4.c
> index b72b34e..e016005 100644
> --- a/hw/acpi/piix4.c
> +++ b/hw/acpi/piix4.c
> @@ -37,6 +37,8 @@
>  #include "hw/acpi/memory_hotplug.h"
>  #include "hw/acpi/acpi_dev_interface.h"
>  
> +extern int qemu_kvm_1_0_compat;
> +
>  //#define DEBUG
>  
>  #ifdef DEBUG

Please dont' put extern declarations in C files.
You lose a useful type-safety compile-time check.

> @@ -200,12 +202,24 @@ static const VMStateDescription vmstate_pci_status = {
>      }
>  };
>  
> +static const VMStateDescription vmstate_acpi_compat;
> +

Don't declare things like this, re-order them in a separate patch so forward
declarations are not necessary.

>  static int acpi_load_old(QEMUFile *f, void *opaque, int version_id)
>  {
>      PIIX4PMState *s = opaque;
>      int ret, i;
>      uint16_t temp;
>  
> +    /* If we are expecting the inbound migration to come from
> +     * qemu-kvm 1.0, it will have a version_id of 2 but really
> +     * be version 3, so call back the original vmstate_load_state
> +     * with a different more tolerant vmstate descriptor
> +     */
> +    if ((version_id == 2) && (qemu_kvm_1_0_compat)) {
> +        return vmstate_load_state(f, &vmstate_acpi_compat,
> +                                  opaque, version_id);
> +    }
> +
>      ret = pci_device_load(PCI_DEVICE(s), f);
>      if (ret < 0) {
>          return ret;
> @@ -267,8 +281,9 @@ static const VMStateDescription vmstate_memhp_state = {
>  };
>  
>  /* qemu-kvm 1.2 uses version 3 but advertised as 2
> - * To support incoming qemu-kvm 1.2 migration, change version_id
> - * and minimum_version_id to 2 below (which breaks migration from
> + * To support incoming qemu-kvm 1.2 migration, we support
> + * via a command line option a change to minimum_version_id
> + * of 2 in a _compat structure (which breaks migration from
>   * qemu 1.2).
>   *
>   */
> @@ -307,6 +322,34 @@ static const VMStateDescription vmstate_acpi = {
>      }
>  };
>  
> +static const VMStateDescription vmstate_acpi_compat = {
> +    .name = "piix4_pm",
> +    .version_id = 3,
> +    .minimum_version_id = 2,
> +    .minimum_version_id_old = 1,
> +    .load_state_old = NULL, /* to avoid recursion */
> +    .post_load = vmstate_acpi_post_load,
> +    .fields      = (VMStateField[]) {
> +        VMSTATE_PCI_DEVICE(parent_obj, PIIX4PMState),
> +        VMSTATE_UINT16(ar.pm1.evt.sts, PIIX4PMState),
> +        VMSTATE_UINT16(ar.pm1.evt.en, PIIX4PMState),
> +        VMSTATE_UINT16(ar.pm1.cnt.cnt, PIIX4PMState),
> +        VMSTATE_STRUCT(apm, PIIX4PMState, 0, vmstate_apm, APMState),
> +        VMSTATE_TIMER(ar.tmr.timer, PIIX4PMState),
> +        VMSTATE_INT64(ar.tmr.overflow_time, PIIX4PMState),
> +        VMSTATE_STRUCT(ar.gpe, PIIX4PMState, 2, vmstate_gpe, ACPIGPE),
> +        VMSTATE_STRUCT_TEST(
> +            acpi_pci_hotplug.acpi_pcihp_pci_status[ACPI_PCIHP_BSEL_DEFAULT],
> +            PIIX4PMState,
> +            vmstate_test_no_use_acpi_pci_hotplug,
> +            2, vmstate_pci_status,
> +            struct AcpiPciHpPciStatus),
> +        VMSTATE_PCI_HOTPLUG(acpi_pci_hotplug, PIIX4PMState,
> +                            vmstate_test_use_acpi_pci_hotplug),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
>  static void piix4_reset(void *opaque)
>  {
>      PIIX4PMState *s = opaque;
> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> index 7081c08..48a4942 100644
> --- a/hw/i386/pc_piix.c
> +++ b/hw/i386/pc_piix.c
> @@ -70,6 +70,8 @@ static bool smbios_legacy_mode;
>  static bool gigabyte_align = true;
>  static bool has_reserved_memory = true;
>  
> +int qemu_kvm_1_0_compat;
> +
>  /* PC hardware initialisation */
>  static void pc_init1(MachineState *machine,
>                       int pci_enabled,
> @@ -386,6 +388,14 @@ static void pc_init_pci_1_2(MachineState *machine)
>      pc_init_pci(machine);
>  }
>  
> +/* PC machine init function for qemu-kvm 1.0 */
> +static void pc_init_pci_1_2_qemu_kvm(MachineState *machine)
> +{
> +    qemu_kvm_1_0_compat = 1;
> +    pc_compat_1_2(machine);
> +    pc_init_pci(machine);
> +}
> +
>  /* PC init function for pc-0.10 to pc-0.13 */
>  static void pc_init_pci_no_kvmclock(MachineState *machine)
>  {
> @@ -644,6 +654,25 @@ static QEMUMachine pc_machine_v1_0 = {
>      .hw_version = "1.0",
>  };
>  
> +#define PC_COMPAT_1_0_QEMU_KVM \
> +        PC_COMPAT_1_0,\
> +        {\
> +            .driver   = "cirrus-vga",\
> +            .property = "vgamem_mb",\
> +            .value    = stringify(16),\
> +        }
> +
> +static QEMUMachine pc_machine_v1_0_qemu_kvm = {
> +    PC_I440FX_1_2_MACHINE_OPTIONS,
> +    .name = "pc-1.0-qemu-kvm",

I think pc-qemu-kvm-1.0 is slightly better - more consistent with
other machine names.

> +    .init = pc_init_pci_1_2_qemu_kvm,
> +    .compat_props = (GlobalProperty[]) {
> +        PC_COMPAT_1_0_QEMU_KVM,
> +        { /* end of list */ }
> +    },
> +    .hw_version = "1.0",
> +};
> +
>  #define PC_COMPAT_0_15 \
>          PC_COMPAT_1_0
>  
> @@ -886,6 +915,7 @@ static void pc_machine_init(void)
>      qemu_register_pc_machine(&pc_machine_v1_2);
>      qemu_register_pc_machine(&pc_machine_v1_1);
>      qemu_register_pc_machine(&pc_machine_v1_0);
> +    qemu_register_pc_machine(&pc_machine_v1_0_qemu_kvm);
>      qemu_register_pc_machine(&pc_machine_v0_15);
>      qemu_register_pc_machine(&pc_machine_v0_14);
>      qemu_register_pc_machine(&pc_machine_v0_13);
> diff --git a/hw/timer/i8254_common.c b/hw/timer/i8254_common.c
> index 07345f6..b4deead 100644
> --- a/hw/timer/i8254_common.c
> +++ b/hw/timer/i8254_common.c
> @@ -29,6 +29,8 @@
>  #include "hw/timer/i8254.h"
>  #include "hw/timer/i8254_internal.h"
>  
> +extern int qemu_kvm_1_0_compat;
> +
>  /* val must be 0 or 1 */
>  void pit_set_gate(ISADevice *dev, int channel, int val)
>  {

Can you add a device property like we do for
other compat behaviours?
That's better than a global variable.
Same for other devices.


> @@ -257,6 +259,11 @@ static int pit_dispatch_post_load(void *opaque, int version_id)
>      return 0;
>  }
>  
> +static bool has_irq_disabled(void *opaque, int version_id)
> +{
> +    return (version_id >= 3) || ((version_id == 2) && qemu_kvm_1_0_compat);
> +}
> +
>  static const VMStateDescription vmstate_pit_common = {
>      .name = "i8254",
>      .version_id = 3,
> @@ -266,7 +273,8 @@ static const VMStateDescription vmstate_pit_common = {
>      .pre_save = pit_dispatch_pre_save,
>      .post_load = pit_dispatch_post_load,
>      .fields = (VMStateField[]) {
> -        VMSTATE_UINT32_V(channels[0].irq_disabled, PITCommonState, 3),
> +        VMSTATE_UINT32_TEST(channels[0].irq_disabled, PITCommonState,
> +                            has_irq_disabled),
>          VMSTATE_STRUCT_ARRAY(channels, PITCommonState, 3, 2,
>                               vmstate_pit_channel, PITChannelState),
>          VMSTATE_INT64(channels[0].next_transition_time,
> -- 
> 1.7.9.5