Re: powerpc/perf: Fix nest-imc cpuhotplug callback failure

[Michael Ellerman]

On Tue, 2017-12-05 at 05:30:38 UTC, Anju T Sudhakar wrote:
> Call trace observed during boot:                                                
>                                                                                 
> Faulting instruction address: 0xc000000000248340                                
> cpu 0x0: Vector: 380 (Data Access Out of Range) at [c000000ff66fb850]           
>     pc: c000000000248340: event_function_call+0x50/0x1f0                        
>     lr: c00000000024878c: perf_remove_from_context+0x3c/0x100                   
>     sp: c000000ff66fbad0                                                        
>    msr: 9000000000009033                                                        
>    dar: 7d20e2a6f92d03c0                                                        
>   current = 0xc000000ff6679200                                                  
>   paca    = 0xc00000000fd40000   softe: 0  irq_happened: 0x01                   
>     pid   = 14, comm = cpuhp/0                                                  
> Linux version 4.14.0-rc2-42789-ge8eae4b (rgrimm@XXXX) (gcc version 5.4.0        
> 20160609 (Ubuntu/IBM 5.4.0-6ubuntu1~16.04.4)) #1 SMP Thu Nov 16 14:35:14 CST    
> 2017                                                                            
> enter ? for help                                                                
> [c000000ff66fbb80] c00000000024878c perf_remove_from_context+0x3c/0x100         
> [c000000ff66fbbc0] c00000000024e84c perf_pmu_migrate_context+0x10c/0x380        
> [c000000ff66fbc60] c0000000000ca050 ppc_nest_imc_cpu_offline+0x1b0/0x210        
> [c000000ff66fbcb0] c0000000000d5d54 cpuhp_invoke_callback+0x194/0x620           
> [c000000ff66fbd20] c0000000000d702c cpuhp_thread_fun+0x7c/0x1b0                 
> [c000000ff66fbd60] c00000000010ad90 smpboot_thread_fn+0x290/0x2a0               
> [c000000ff66fbdc0] c000000000104818 kthread+0x168/0x1b0                         
> [c000000ff66fbe30] c00000000000b5a0 ret_from_kernel_thread+0x5c/0xbc            
>                                                                                 
> While registering the cpuhotplug callbacks for nest-imc, if we fail in the      
> cpuhotplug online path for any random node in a multi node system (because      
> the opal call to stop nest-imc counters fails for that node),                   
> ppc_nest_imc_cpu_offline() will get invoked for other nodes who successfully    
> returned from cpuhotplug online path.                                           
>                                                                                 
> This call trace is generated since in the ppc_nest_imc_cpu_offline()            
> path we are trying to migrate the event context, when nest-imc counters are     
> not even initialized.                                                           
>                                                                                 
> Patch to add a check to ensure that nest-imc is registered before migrating     
> the event context.                                     
> 
> Note:                                                                           
> Madhavan Srinivasan has recently send a skiboot patch to have a check in the    
> skiboot code to make sure that the  microcode is initialized in all the chips,  
> before enabling the nest units.                                                 
> https://patchwork.ozlabs.org/patch/844047/ (v2)
>                                                                                 
> Signed-off-by: Anju T Sudhakar <anju@xxxxxxxxxxxxxxxxxx>  
> Reviewed-by: Madhavan Srinivasan <maddy@xxxxxxxxxxxxxxxxxx>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/ad2b6e01024ef23bddc3ce0bcb115e

cheers