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powerpc/perf: Fix IMC allocation routine 

When setting nr_cpus=1, we observed a crash in IMC code during boot
due to a missing allocation: basically, IMC code is taking the number
of threads into account in imc_mem_init() and if we manually set
nr_cpus for a value that is not multiple of the number of threads per
core, an integer division in that function will discard the decimal
portion, leading IMC to not allocate one mem_info struct. This causes
a NULL pointer dereference later, on is_core_imc_mem_inited().

This patch just rounds that division up, fixing the bug.

Signed-off-by: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com>
Acked-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Guilherme G. Piccoli 2017-10-19 17:41:33 -02:00 committed by Michael Ellerman
parent 0d8ba16278
commit 0b167f1108
1 changed files with 2 additions and 2 deletions
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4
arch/powerpc/perf/imc-pmu.c
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@ -1104,7 +1104,7 @@ static int init_nest_pmu_ref(void)
static void cleanup_all_core_imc_memory(void)
{
int i, nr_cores = num_present_cpus() / threads_per_core;
int i, nr_cores = DIV_ROUND_UP(num_present_cpus(), threads_per_core);
struct imc_mem_info *ptr = core_imc_pmu->mem_info;
int size = core_imc_pmu->counter_mem_size;
@ -1212,7 +1212,7 @@ static int imc_mem_init(struct imc_pmu *pmu_ptr, struct device_node *parent,
if (!pmu_ptr->pmu.name)
return -ENOMEM;
nr_cores = num_present_cpus() / threads_per_core;
nr_cores = DIV_ROUND_UP(num_present_cpus(), threads_per_core);
pmu_ptr->mem_info = kcalloc(nr_cores, sizeof(struct imc_mem_info),
GFP_KERNEL);