Re: [PATCH] x86/hyperv: LP creation with lp_index on same CPU-id

[Praveen Kumar <kumarpraveen@linux.microsoft.com>]

On 5/31/2021 4:27 PM, Wei Liu wrote:
> On Mon, May 31, 2021 at 01:10:46PM +0530, Praveen Kumar wrote:
>> The hypervisor expects the lp_index to be same as cpu-id during LP creation
>> This fix correct the same, as cpu_physical_id can give different cpu-id.
> 
> Code looks fine to me, but the commit message can be made clearer.
> 
> """
> The hypervisor expects the logical processor index to be the same as
> CPU's id during logical processor creation. Using cpu_physical_id
> confuses Microsoft Hypervisor's scheduler. That causes the root
> partition not boot when core scheduler is used.
> 
> This patch removes the call to cpu_physical_id and uses the CPU index
> directly for bringing up logical processor. This scheme works for both
> classic scheduler and core scheduler.
> 
> Fixes: 333abaf5abb3 (x86/hyperv: implement and use hv_smp_prepare_cpus)
> """
> 
> No action is required from you. If you are fine with this commit message
> I can incorporate it and update the subject line when committing this
> patch.
> 

Thanks Wei for your comments. I'm fine with your inputs. Please go ahead. Thanks.

Regards,

~Praveen.

>>
>> Signed-off-by: Praveen Kumar <kumarpraveen@linux.microsoft.com>
>> ---
>>  arch/x86/kernel/cpu/mshyperv.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
>> index 22f13343b5da..4fa0a4280895 100644
>> --- a/arch/x86/kernel/cpu/mshyperv.c
>> +++ b/arch/x86/kernel/cpu/mshyperv.c
>> @@ -236,7 +236,7 @@ static void __init hv_smp_prepare_cpus(unsigned int max_cpus)
>>  	for_each_present_cpu(i) {
>>  		if (i == 0)
>>  			continue;
>> -		ret = hv_call_add_logical_proc(numa_cpu_node(i), i, cpu_physical_id(i));
>> +		ret = hv_call_add_logical_proc(numa_cpu_node(i), i, i);
>>  		BUG_ON(ret);
>>  	}
>>  
>> -- 
>> 2.25.1
>>