Re: [PATCH v3 07/18] machine: Add a new function init_apicid_fn in MachineClass

From: Babu Moger <babu.moger@amd.com>
To: Eduardo Habkost <ehabkost@redhat.com>
Cc: mst@redhat.com, armbru@redhat.com, qemu-devel@nongnu.org,
	pbonzini@redhat.com, Igor Mammedov <imammedo@redhat.com>,
	rth@twiddle.net
Subject: Re: [PATCH v3 07/18] machine: Add a new function init_apicid_fn in MachineClass
Date: Wed, 29 Jan 2020 11:05:09 -0600	[thread overview]
Message-ID: <f930f097-2b75-799a-f2cf-3aaa9164c798@amd.com> (raw)
In-Reply-To: <20200129165133.GR18770@habkost.net>

On 1/29/20 10:51 AM, Eduardo Habkost wrote:
> On Wed, Jan 29, 2020 at 10:32:01AM -0600, Babu Moger wrote:
>>
>>
>> On 1/29/20 3:14 AM, Igor Mammedov wrote:
>>> On Tue, 28 Jan 2020 13:45:31 -0600
>>> Babu Moger <babu.moger@amd.com> wrote:
>>>
>>>> On 1/28/20 10:29 AM, Igor Mammedov wrote:
>>>>> On Tue, 03 Dec 2019 18:37:42 -0600
>>>>> Babu Moger <babu.moger@amd.com> wrote:
>>>>>   
>>>>>> Add a new function init_apicid_fn in MachineClass to initialize the mode
>>>>>> specific handlers to decode the apic ids.
>>>>>>
>>>>>> Signed-off-by: Babu Moger <babu.moger@amd.com>
>>>>>> ---
>>>>>>  include/hw/boards.h |    1 +
>>>>>>  vl.c                |    3 +++
>>>>>>  2 files changed, 4 insertions(+)
>>>>>>
>>>>>> diff --git a/include/hw/boards.h b/include/hw/boards.h
>>>>>> index d4fab218e6..ce5aa365cb 100644
>>>>>> --- a/include/hw/boards.h
>>>>>> +++ b/include/hw/boards.h
>>>>>> @@ -238,6 +238,7 @@ struct MachineClass {
>>>>>>                                                           unsigned cpu_index);
>>>>>>      const CPUArchIdList *(*possible_cpu_arch_ids)(MachineState *machine);
>>>>>>      int64_t (*get_default_cpu_node_id)(const MachineState *ms, int idx);
>>>>>> +    void (*init_apicid_fn)(MachineState *ms);  
>>>>> it's x86 specific, so why it wasn put into PCMachineClass?  
>>>>
>>>> Yes. It is x86 specific for now. I tried to make it generic function so
>>>> other OSes can use it if required(like we have done in
>>>> possible_cpu_arch_ids). It initializes functions required to build the
>>>> apicid for each CPUs. We need these functions much early in the
>>>> initialization. It should be initialized before parse_numa_opts or
>>>> machine_run_board_init(in v1.c) which are called from generic context. We
>>>> cannot use PCMachineClass at this time.
>>>
>>> could you point to specific patches in this series that require
>>> apic ids being initialized before parse_numa_opts and elaborate why?
>>>
>>> we already have possible_cpu_arch_ids() which could be called very
>>> early and calculates APIC IDs in x86 case, so why not reuse it?
>>
>> Forgot to respond to this. The possible_cpu_arch_ids does not use the numa
>> information to build the apic id. We cannot re-use it without changing it
>> drastically.
> 
> I don't get it.  I see multiple patches in this series changing
> pc_possible_cpu_arch_ids() (which is really expected, if you are
> changing how APIC IDs are generated).
> 

My bad. I mispoke on that.I should have said the current decoding
logic(x86_apicid_from_cpu_idx, x86_topo_ids_from_apicid,
x86_apicid_from_topo_ids) cannot be used as is.