[v2] powerpc/perf: Fix memory allocation for core-imc based on num_possible_cpus()

[Michael Ellerman]

On Wed, 2018-05-16 at 06:35:18 UTC, Anju T Sudhakar wrote:
> Currently memory is allocated for core-imc based on cpu_present_mask,
> which has bit 'cpu' set iff cpu is populated. We use (cpu number / threads
> per core) as the array index to access the memory.
> 
> Under some circumstances firmware marks a CPU as GUARDed CPU and boot the
> system, until cleared of errors, these CPU's are unavailable for all
> subsequent boots. GUARDed CPUs are possible but not present from linux
> view, so it blows a hole when we assume the max length of our allocation
> is driven by our max present cpus, where as one of the cpus might be online
> and be beyond the max present cpus, due to the hole. 
> So (cpu number / threads per core) value bounds the array index and leads
> to memory overflow.
> 
> Call trace observed during a guard test:
> 
> Faulting instruction address: 0xc000000000149f1c
> cpu 0x69: Vector: 380 (Data Access Out of Range) at [c000003fea303420]
>     pc:c000000000149f1c: prefetch_freepointer+0x14/0x30
>     lr:c00000000014e0f8: __kmalloc+0x1a8/0x1ac
>     sp:c000003fea3036a0
>    msr:9000000000009033
>    dar:c9c54b2c91dbf6b7
>   current = 0xc000003fea2c0000
>   paca    = 0xc00000000fddd880	 softe: 3	 irq_happened: 0x01
>     pid   = 1, comm = swapper/104
> Linux version 4.16.7-openpower1 (smc at smc-desktop) (gcc version 6.4.0
> (Buildroot 2018.02.1-00006-ga8d1126)) #2 SMP Fri May 4 16:44:54 PDT 2018
> enter ? for help
> call trace:
> 	 __kmalloc+0x1a8/0x1ac
> 	 (unreliable)
> 	 init_imc_pmu+0x7f4/0xbf0
> 	 opal_imc_counters_probe+0x3fc/0x43c
> 	 platform_drv_probe+0x48/0x80
> 	 driver_probe_device+0x22c/0x308
> 	 __driver_attach+0xa0/0xd8
> 	 bus_for_each_dev+0x88/0xb4
> 	 driver_attach+0x2c/0x40
> 	 bus_add_driver+0x1e8/0x228
> 	 driver_register+0xd0/0x114
> 	 __platform_driver_register+0x50/0x64
> 	 opal_imc_driver_init+0x24/0x38
> 	 do_one_initcall+0x150/0x15c
> 	 kernel_init_freeable+0x250/0x254
> 	 kernel_init+0x1c/0x150
> 	 ret_from_kernel_thread+0x5c/0xc8
> 
> Allocating memory for core-imc based on cpu_possible_mask, which has
> bit 'cpu' set iff cpu is populatable, will fix this issue.
> 
> Reported-by: Pridhiviraj Paidipeddi <ppaidipe at linux.vnet.ibm.com>
> Signed-off-by: Anju T Sudhakar <anju at linux.vnet.ibm.com>
> Reviewed-by: Balbir Singh <bsingharora at gmail.com>
> Tested-by: Pridhiviraj Paidipeddi <ppaidipe at linux.vnet.ibm.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/d2032678e57fc508d7878307badde8

cheers