* [PATCH] powerpc/perf: Fix IMC allocation routine
@ 2017-10-19 19:41 Guilherme G. Piccoli
2017-10-24 8:34 ` Anju T Sudhakar
2017-11-01 5:17 ` Michael Ellerman
0 siblings, 2 replies; 4+ messages in thread
From: Guilherme G. Piccoli @ 2017-10-19 19:41 UTC (permalink / raw)
To: linuxppc-dev; +Cc: gpiccoli, benh, paulus, mpe, anju
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>
---
Anju, looks good to you? Tested in P9 with latest FW available.
arch/powerpc/perf/imc-pmu.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c
index 88126245881b..92ae5de0bbac 100644
--- a/arch/powerpc/perf/imc-pmu.c
+++ b/arch/powerpc/perf/imc-pmu.c
@@ -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);
--
2.14.2
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] powerpc/perf: Fix IMC allocation routine
2017-10-19 19:41 [PATCH] powerpc/perf: Fix IMC allocation routine Guilherme G. Piccoli
@ 2017-10-24 8:34 ` Anju T Sudhakar
2017-10-24 12:17 ` Guilherme G. Piccoli
2017-11-01 5:17 ` Michael Ellerman
1 sibling, 1 reply; 4+ messages in thread
From: Anju T Sudhakar @ 2017-10-24 8:34 UTC (permalink / raw)
To: Guilherme G. Piccoli, linuxppc-dev; +Cc: benh, paulus, mpe
[-- Attachment #1: Type: text/plain, Size: 1872 bytes --]
Hi Guilherme,
Nice catch.
On Friday 20 October 2017 01:11 AM, Guilherme G. Piccoli wrote:
> 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>
> ---
> Anju, looks good to you? Tested in P9 with latest FW available.
>
> arch/powerpc/perf/imc-pmu.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c
> index 88126245881b..92ae5de0bbac 100644
> --- a/arch/powerpc/perf/imc-pmu.c
> +++ b/arch/powerpc/perf/imc-pmu.c
> @@ -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);
>
Thanks,
Anju
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] powerpc/perf: Fix IMC allocation routine
2017-10-24 8:34 ` Anju T Sudhakar
@ 2017-10-24 12:17 ` Guilherme G. Piccoli
0 siblings, 0 replies; 4+ messages in thread
From: Guilherme G. Piccoli @ 2017-10-24 12:17 UTC (permalink / raw)
To: Anju T Sudhakar; +Cc: linuxppc-dev, benh, paulus, mpe
On 10/24/2017 06:34 AM, Anju T Sudhakar wrote:
> Hi Guilherme,
>
> Nice catch.
>
> On Friday 20 October 2017 01:11 AM, Guilherme G. Piccoli wrote:
>> 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>
Thanks Anju :)
>> ---
>> Anju, looks good to you? Tested in P9 with latest FW available.
>>
>> arch/powerpc/perf/imc-pmu.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c
>> index 88126245881b..92ae5de0bbac 100644
>> --- a/arch/powerpc/perf/imc-pmu.c
>> +++ b/arch/powerpc/perf/imc-pmu.c
>> @@ -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);
>>
>
> Thanks,
> Anju
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: powerpc/perf: Fix IMC allocation routine
2017-10-19 19:41 [PATCH] powerpc/perf: Fix IMC allocation routine Guilherme G. Piccoli
2017-10-24 8:34 ` Anju T Sudhakar
@ 2017-11-01 5:17 ` Michael Ellerman
1 sibling, 0 replies; 4+ messages in thread
From: Michael Ellerman @ 2017-11-01 5:17 UTC (permalink / raw)
To: Guilherme G. Piccoli, linuxppc-dev; +Cc: anju, paulus, gpiccoli
On Thu, 2017-10-19 at 19:41:33 UTC, "Guilherme G. Piccoli" wrote:
> 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>
Applied to powerpc fixes, thanks.
https://git.kernel.org/powerpc/c/0b167f11085a34281349f395d20005
cheers
^ permalink raw reply [flat|nested] 4+ messages in thread
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2017-10-19 19:41 [PATCH] powerpc/perf: Fix IMC allocation routine Guilherme G. Piccoli
2017-10-24 8:34 ` Anju T Sudhakar
2017-10-24 12:17 ` Guilherme G. Piccoli
2017-11-01 5:17 ` Michael Ellerman
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