[Qemu-devel] Re: [PATCH v4 03/10] x86: Extend validity of cpu_is_bsp

[Jan Kiszka]

Gleb Natapov wrote:
> On Mon, Mar 01, 2010 at 06:17:22PM +0100, Jan Kiszka wrote:
>> As we hard-wire the BSP to CPU 0 anyway and cpuid_apic_id equals
>> cpu_index, cpu_is_bsp can also be based on the latter directly. This
>> will help an early user of it: KVM while initializing mp_state.
>>
>> Signed-off-by: Jan Kiszka <address@hidden>
>> ---
>>  hw/pc.c |    3 ++-
>>  1 files changed, 2 insertions(+), 1 deletions(-)
>>
>> diff --git a/hw/pc.c b/hw/pc.c
>> index b90a79e..58c32ea 100644
>> --- a/hw/pc.c
>> +++ b/hw/pc.c
>> @@ -767,7 +767,8 @@ static void pc_init_ne2k_isa(NICInfo *nd)
>>  
>>  int cpu_is_bsp(CPUState *env)
>>  {
>> -    return env->cpuid_apic_id == 0;
>> +    /* We hard-wire the BSP to the first CPU. */
>> +    return env->cpu_index == 0;
>>  }
> We should not assume that. The function was written like that
> specifically so the code around it will not rely on this assumption.
> Now you change that specifically to write code that will do incorrect
> assumptions. I don't see the logic here.

The logic is that we do not support any other mapping yet - with or
without this change. Without it, we complicate the APIC initialization
for (so far) no good reason. Once we want to support different BSP
assignments, we need to go through the code and rework some parts anyway.

Jan

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