Re: [Qemu-devel] [PATCH v17 01/10] hw/arm/virt: Add RAS platform version for migration

[Igor Mammedov <imammedo@redhat.com>]

On Tue, 14 May 2019 04:18:14 -0700
Dongjiu Geng <gengdongjiu@huawei.com> wrote:

> Support this feature since version 4.1, disable it by
> default in the old version.
> 
> Signed-off-by: Dongjiu Geng <gengdongjiu@huawei.com>
> ---
>  hw/arm/virt.c         | 6 ++++++
>  include/hw/arm/virt.h | 1 +
>  2 files changed, 7 insertions(+)
> 
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 5331ab7..7bdd41b 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -2043,8 +2043,14 @@ DEFINE_VIRT_MACHINE_AS_LATEST(4, 1)
>  
>  static void virt_machine_4_0_options(MachineClass *mc)
>  {
> +    VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc));
> +
>      virt_machine_4_1_options(mc);
>      compat_props_add(mc->compat_props, hw_compat_4_0, hw_compat_4_0_len);
> +    /* Disable memory recovery feature for 4.0 as RAS support was
> +     * introduced with 4.1.
> +     */
> +    vmc->no_ras = true;

So it would mean that the feature is enabled unconditionally for
new machine types and consumes resources whether user needs it or not.

In light of the race for leaner QEMU and faster startup times,
it might be better to make RAS optional and make user explicitly
enable it using a machine option.


>  }
>  DEFINE_VIRT_MACHINE(4, 0)
>  
> diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
> index 4240709..7f1a033 100644
> --- a/include/hw/arm/virt.h
> +++ b/include/hw/arm/virt.h
> @@ -104,6 +104,7 @@ typedef struct {
>      bool disallow_affinity_adjustment;
>      bool no_its;
>      bool no_pmu;
> +    bool no_ras;
>      bool claim_edge_triggered_timers;
>      bool smbios_old_sys_ver;
>      bool no_highmem_ecam;