Date:   Fri, 19 Aug 2016 09:41:35 +0530
From:   Ganapatrao Kulkarni <gpkulkarni@...il.com>
To:     zhong jiang <zhongjiang@...wei.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Mark Rutland <mark.rutland@....com>,
        Will Deacon <will.deacon@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Ganapatrao Kulkarni <gkulkarni@...iumnetworks.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] mm, numa: boot cpu should bound to the node0 when
 node_off enable

On Fri, Aug 19, 2016 at 9:30 AM, Ganapatrao Kulkarni
<gpkulkarni@...il.com> wrote:
> On Fri, Aug 19, 2016 at 7:28 AM, zhong jiang <zhongjiang@...wei.com> wrote:
>> On 2016/8/19 1:45, Ganapatrao Kulkarni wrote:
>>> On Thu, Aug 18, 2016 at 9:34 PM, Catalin Marinas
>>> <catalin.marinas@....com> wrote:
>>>> On Thu, Aug 18, 2016 at 09:09:26PM +0800, zhongjiang wrote:
>>>>> At present, boot cpu will bound to a node from device tree when node_off enable.
>>>>> if the node is not initialization, it will lead to a following problem.
>>>>>
>>>>>  next_zones_zonelist+0x18/0x80
>>>>>  __build_all_zonelists+0x1e0/0x288
>>>>>  build_all_zonelists_init+0x10/0x1c
>>>>>  build_all_zonelists+0x114/0x128
>>>>>  start_kernel+0x1a0/0x414
>>>> I think this "problem" is missing a lot of information. Is this supposed
>>>> to be a kernel panic?
>>>>
>>>>> The patch fix it by fallback to node 0. therefore, the cpu will bound to the node
>>>>> correctly.
>>>>>
>>>>> Signed-off-by: zhongjiang <zhongjiang@...wei.com>
>>>>> ---
>>>>>  arch/arm64/mm/numa.c | 2 +-
>>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
>>>>> index 4dcd7d6..1f8f5da 100644
>>>>> --- a/arch/arm64/mm/numa.c
>>>>> +++ b/arch/arm64/mm/numa.c
>>>>> @@ -119,7 +119,7 @@ void numa_store_cpu_info(unsigned int cpu)
>>>>>  void __init early_map_cpu_to_node(unsigned int cpu, int nid)
>>>>>  {
>>>>>       /* fallback to node 0 */
>>>>> -     if (nid < 0 || nid >= MAX_NUMNODES)
>>>>> +     if (nid < 0 || nid >= MAX_NUMNODES || numa_off)
>>> i  did not understood how this line change fixes the issue that you
>>> have mentioned (i too not understood fully the issue description)
>>> this array used while mapping node id when secondary cores comes up
>>> when numa_off is set the cpu_to_node_map[cpu] is not used and set to
>>> node0 always( refer function numa_store_cpu_info)..
>>> please provide more details to understand the issue you are facing.
>>> /*
>>>  *  Set the cpu to node and mem mapping
>>>  */
>>> void numa_store_cpu_info(unsigned int cpu)
>>> {
>>>         map_cpu_to_node(cpu, numa_off ? 0 : cpu_to_node_map[cpu]);
>>> }
>>>
>>> thanks
>>> Ganapat
>> The issue comes up when we test the kdump. it will leads to kernel crash.
>> when I debug the issue, I find boot cpu actually bound to the node1. while
>> node1 is not real existence when numa_off enable.
>
> boot cpu is default mapped to node0
> are you running with any other patches?

if you added any patch to change this code
  /* init boot processor */
        cpu_to_node_map[0] = 0;
        map_cpu_to_node(0, 0);

then adding code to take-care numa_off here might solve your issue.

>>
>> __build_all_zonelists will call the cpu_to_node[cpu], but orresponding relation
>> will be obtained from the devicetree. therefore, the issue will come up.
>
> when numa_off, all cpus are mapped to node0( refer
> numa_store_cpu_info) and device tree mapping is ignored.
>> The corresponding message is as follows when kdump start. it is obvious that mem
>> range points to the node1 in the devicetree.
>>
>> Early memory node ranges
>> node   0: [mem 0x0000005fe0000000-0x0000005fffffffff]
>> Initmem setup node 0 [mem 0x0000005fe0000000-0x0000005fffffffff]
>>
>> Unable to handle kernel paging request at virtual address 00001690
>> pgd = ffff800001226000
>> [00001690] *pgd=0000000000000000
>> Internal error: Oops: 96000004 [#1] SMP
>>  Modules linked in:
>> CPU: 0 PID: 0 Comm: swapper Not tainted 4.1.27-vhulk3.6.5.aarch64 #1
>> Hardware name: Hisilicon Hi1612 Development Board (DT)
>>  task: ffff80000102b730 ti: ffff800001018000 task.ti: ffff800001018000
>> PC is at next_zones_zonelist+0x18/0x80
>>  LR is at __build_all_zonelists+0x1e0/0x288
>> next_zones_zonelist+0x18/0x80
>>  __build_all_zonelists+0x1e0/0x288
>> build_all_zonelists_init+0x10/0x1c
>>  build_all_zonelists+0x114/0x128
>>  start_kernel+0x1a0/0x414
>>>>>               nid = 0;
>>>>>
>>>>>       cpu_to_node_map[cpu] = nid;
>>>> The patch looks fine (slight inconsistence from the map_cpu_to_node()
>>>> callers but I guess we don't want to expose numa_off outside this file).
>>>> I would however like to see an Ack from Ganapat (cc'ed).
>>>>
>>>> --
>>>> Catalin
>>>>
>>>> _______________________________________________
>>>> linux-arm-kernel mailing list
>>>> linux-arm-kernel@...ts.infradead.org
>>>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>>> .
>>>
>>
>>

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