Re: [Qemu-devel] [Update PATCH V2] x86: Increase max vcpu number to 8192

[Eduardo Habkost <ehabkost@redhat.com>]

On Thu, Aug 10, 2017 at 10:26:06PM -0400, Lan Tianyu wrote:
> Intel Xeon phi chip will support 352 logical threads. For HPC
> usage case, it will create a huge VM with vcpus number as same as host
> cpus. This patch is to increase max vcpu number from 288 to 8192 which
> is current default maximum cpu number for Linux kernel.
> 
> Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
> ---
> Change since v1:
> 	* Bump max vcpu number from 352 to 8192
> 	* Add compat support for new max vcpu limitation
> 
>  hw/i386/pc_q35.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
> index 169a214..e093601 100644
> --- a/hw/i386/pc_q35.c
> +++ b/hw/i386/pc_q35.c
> @@ -299,13 +299,21 @@ static void pc_q35_machine_options(MachineClass *m)
>      m->default_display = "std";
>      m->no_floppy = 1;
>      m->has_dynamic_sysbus = true;
> -    m->max_cpus = 288;
> +    m->max_cpus = 8192;
>  }
>  
> +static void pc_q35_2_11_machine_options(MachineClass *m)
> +{
> +     pc_q35_machine_options(m);
> +     m->alias = "q35";
> +}
> +DEFINE_Q35_MACHINE(v2_11, "pc-q35-2.11", NULL,
> +                   pc_q35_2_11_machine_options);
> +
>  static void pc_q35_2_10_machine_options(MachineClass *m)
>  {
> -    pc_q35_machine_options(m);
> -    m->alias = "q35";
> +    pc_q35_2_11_machine_options(m);

You need m->alias=NULL here.

> +    m->max_cpus = 288;
>      m->numa_auto_assign_ram = numa_legacy_auto_assign_ram;
>  }
>  

Please add the pc-*-2.11 machine-types in a separate patch.  This
way we can add the new machine-types in other series/trees and
deal more easily with conflicts.

You can use commit 465238d9f873a6251223db1669aa4766822a8783
("pc: add 2.10 machine type") as reference.

-- 
Eduardo