Re: [PATCH v2] hw/i386: Move save_tsc_khz from PCMachineClass to X86MachineClass

[Sergio Lopez <slp@redhat.com>]

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Liam Merwick <liam.merwick@oracle.com> writes:

> Attempting to migrate a VM using the microvm machine class results in the source
> QEMU aborting with the following message/backtrace:
>
> target/i386/machine.c:955:tsc_khz_needed: Object 0x555556608fa0 is not an
> instance of type generic-pc-machine
>
> abort()
> object_class_dynamic_cast_assert()
> vmstate_save_state_v()
> vmstate_save_state()
> vmstate_save()
> qemu_savevm_state_complete_precopy()
> migration_thread()
> migration_thread()
> migration_thread()
> qemu_thread_start()
> start_thread()
> clone()
>
> The access to the machine class returned by MACHINE_GET_CLASS() in
> tsc_khz_needed() is crashing as it is trying to dereference a different
> type of machine class object (TYPE_PC_MACHINE) to that of this microVM.
>
> This can be resolved by extending the changes in the following commit
> f0bb276bf8d5 ("hw/i386: split PCMachineState deriving X86MachineState from it")
> and moving the save_tsc_khz field in PCMachineClass to X86MachineClass.
>
> Fixes: f0bb276bf8d5 ("hw/i386: split PCMachineState deriving X86MachineState from it")
> Signed-off-by: Liam Merwick <liam.merwick@oracle.com>
> Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
> ---
>
> v1 -> v2 - fix SHA1 of patch being referenced.
>
>  hw/i386/pc.c          | 1 -
>  hw/i386/pc_piix.c     | 4 ++--
>  hw/i386/pc_q35.c      | 4 ++--
>  hw/i386/x86.c         | 1 +
>  include/hw/i386/pc.h  | 2 --
>  include/hw/i386/x86.h | 2 ++
>  target/i386/machine.c | 4 ++--
>  7 files changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 96715f8a3f99..ac08e6360437 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -2195,7 +2195,6 @@ static void pc_machine_class_init(ObjectClass *oc, void *data)
>      /* BIOS ACPI tables: 128K. Other BIOS datastructures: less than 4K reported
>       * to be used at the moment, 32K should be enough for a while.  */
>      pcmc->acpi_data_size = 0x20000 + 0x8000;
> -    pcmc->save_tsc_khz = true;
>      pcmc->linuxboot_dma_enabled = true;
>      pcmc->pvh_enabled = true;
>      assert(!mc->get_hotplug_handler);
> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> index 2aefa3b8dfe3..0548c259dc74 100644
> --- a/hw/i386/pc_piix.c
> +++ b/hw/i386/pc_piix.c
> @@ -567,10 +567,10 @@ DEFINE_I440FX_MACHINE(v2_6, "pc-i440fx-2.6", NULL,
>  
>  static void pc_i440fx_2_5_machine_options(MachineClass *m)
>  {
> -    PCMachineClass *pcmc = PC_MACHINE_CLASS(m);
> +    X86MachineClass *x86mc = X86_MACHINE_CLASS(m);
>  
>      pc_i440fx_2_6_machine_options(m);
> -    pcmc->save_tsc_khz = false;
> +    x86mc->save_tsc_khz = false;
>      m->legacy_fw_cfg_order = 1;
>      compat_props_add(m->compat_props, hw_compat_2_5, hw_compat_2_5_len);
>      compat_props_add(m->compat_props, pc_compat_2_5, pc_compat_2_5_len);
> diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
> index d51f5247276d..385e5cffb167 100644
> --- a/hw/i386/pc_q35.c
> +++ b/hw/i386/pc_q35.c
> @@ -508,10 +508,10 @@ DEFINE_Q35_MACHINE(v2_6, "pc-q35-2.6", NULL,
>  
>  static void pc_q35_2_5_machine_options(MachineClass *m)
>  {
> -    PCMachineClass *pcmc = PC_MACHINE_CLASS(m);
> +    X86MachineClass *x86mc = X86_MACHINE_CLASS(m);
>  
>      pc_q35_2_6_machine_options(m);
> -    pcmc->save_tsc_khz = false;
> +    x86mc->save_tsc_khz = false;
>      m->legacy_fw_cfg_order = 1;
>      compat_props_add(m->compat_props, hw_compat_2_5, hw_compat_2_5_len);
>      compat_props_add(m->compat_props, pc_compat_2_5, pc_compat_2_5_len);
> diff --git a/hw/i386/x86.c b/hw/i386/x86.c
> index fd84b23124e6..394edc2f7209 100644
> --- a/hw/i386/x86.c
> +++ b/hw/i386/x86.c
> @@ -763,6 +763,7 @@ static void x86_machine_class_init(ObjectClass *oc, void *data)
>      mc->get_default_cpu_node_id = x86_get_default_cpu_node_id;
>      mc->possible_cpu_arch_ids = x86_possible_cpu_arch_ids;
>      x86mc->compat_apic_id_mode = false;
> +    x86mc->save_tsc_khz = true;
>      nc->nmi_monitor_handler = x86_nmi;
>  
>      object_class_property_add(oc, X86_MACHINE_MAX_RAM_BELOW_4G, "size",
> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index e6fa8418ca61..1f86eba3f998 100644
> --- a/include/hw/i386/pc.h
> +++ b/include/hw/i386/pc.h
> @@ -116,8 +116,6 @@ typedef struct PCMachineClass {
>      bool enforce_aligned_dimm;
>      bool broken_reserved_end;
>  
> -    /* TSC rate migration: */
> -    bool save_tsc_khz;
>      /* generate legacy CPU hotplug AML */
>      bool legacy_cpu_hotplug;
>  
> diff --git a/include/hw/i386/x86.h b/include/hw/i386/x86.h
> index 82d09fd7d099..4b8491788526 100644
> --- a/include/hw/i386/x86.h
> +++ b/include/hw/i386/x86.h
> @@ -30,6 +30,8 @@ typedef struct {
>  
>      /*< public >*/
>  
> +    /* TSC rate migration: */
> +    bool save_tsc_khz;
>      /* Enables contiguous-apic-ID mode */
>      bool compat_apic_id_mode;
>  } X86MachineClass;
> diff --git a/target/i386/machine.c b/target/i386/machine.c
> index 6481f846f6e9..7bdeb7815755 100644
> --- a/target/i386/machine.c
> +++ b/target/i386/machine.c
> @@ -988,8 +988,8 @@ static bool tsc_khz_needed(void *opaque)
>      X86CPU *cpu = opaque;
>      CPUX86State *env = &cpu->env;
>      MachineClass *mc = MACHINE_GET_CLASS(qdev_get_machine());
> -    PCMachineClass *pcmc = PC_MACHINE_CLASS(mc);
> -    return env->tsc_khz && pcmc->save_tsc_khz;
> +    X86MachineClass *x86mc = X86_MACHINE_CLASS(mc);
> +    return env->tsc_khz && x86mc->save_tsc_khz;
>  }
>  
>  static const VMStateDescription vmstate_tsc_khz = {

LGTM, thanks.

Reviewed-by: Sergio Lopez <slp@redhat.com>

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