Re: [Qemu-devel] [PATCH 22/27] pc: set CPU APIC ID explicitly

[Igor Mammedov <imammedo@redhat.com>]

On Wed, 24 Oct 2012 15:49:56 -0200
Eduardo Habkost <ehabkost@redhat.com> wrote:

> The PC code takes care of CPU topology, and CPU topology affect the CPU
> APIC ID. So the PC CPU initialization code needs to set the APIC ID
> explicitly.
> 
> By now, keep the existing behavior but create a apic_id_for_cpu()
> function that will be changed later to implement appropriate
> topology-dependent behavior.
> 
> The cpuid_apic_id field is used only at:
> 
>  - x86_cpu_apic_init(), called from x86_cpu_realize()
>  - kvm_init_vcpu(), that is called from the VCPU thread
>    created by qemu_init_vcpu(), called by x86_cpu_realize()
>  - helper_cpuid(), called only when the VCPU is already running
>  - kvm_arch_init_vcpu(), that's called by kvm_init_vcpu()
> 
> So it's safe to change it before x86_cpu_realize() is called.
> 
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
> This is based on the patch that I have originally suybmitted as:
>  Subject: pc: create apic_id_for_cpu() function (v3)
> ---
>  hw/pc.c | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/hw/pc.c b/hw/pc.c
> index 0e9a00f..eb68851 100644
> --- a/hw/pc.c
> +++ b/hw/pc.c
> @@ -553,6 +553,21 @@ static void bochs_bios_write(void *opaque, uint32_t
> addr, uint32_t val) }
>  }
>  
> +/* Calculates initial APIC ID for a specific CPU index
> + *
> + * Currently we need to be able to calculate the APIC ID from the CPU index
> + * alone (without requiring a CPU object), as the QEMU<->Seabios
> interfaces have
> + * no concept of "CPU index", and the NUMA tables on fw_cfg need the APIC
> ID of
> + * all CPUs up to max_cpus.
> + */
> +static uint32_t apic_id_for_cpu(PCInitArgs *args, int cpu_index)
> +{
> +    /* right now APIC ID == CPU index. this will eventually change to use
> +     * the CPU topology configuration properly
> +     */
> +    return cpu_index;
> +}
> +
>  int e820_add_entry(uint64_t address, uint64_t length, uint32_t type)
>  {
>      int index = le32_to_cpu(e820_table.count);
> @@ -870,6 +885,13 @@ static void pc_cpu_init(PCInitArgs *args, int
> cpu_index) exit(1);
>      }
>  
> +    /* Override the default APIC set by the X86CPU init function.
> +     * We need to do that because:
> +     * - The APIC ID depends on the CPU topology;
> +     * - The exact APIC ID used may depend on the machine-type init
> arguments.
> +     */
> +    cpu->env.cpuid_apic_id = apic_id_for_cpu(args, cpu_index);
Could you create property setter for apic_id and use it here, please.

> +
>      x86_cpu_realize(OBJECT(cpu), &err);
>      if (err) {
>          error_report("pc_cpu_init: %s\n", error_get_pretty(err));