On 2018-05-16 12:05, 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@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 <ppaid...@linux.vnet.ibm.com>
Signed-off-by: Anju T Sudhakar <a...@linux.vnet.ibm.com>
Reviewed-by: Balbir Singh <bsinghar...@gmail.com>
I have verified this fix with both normal and kexec boot multiple times
when
system is having GARDed cores. Not seen any crash/memory corruption
issues with
this.
Tested-by: Pridhiviraj Paidipeddi <ppaid...@linux.vnet.ibm.com>
---
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 d7532e7..75fb23c 100644
--- a/arch/powerpc/perf/imc-pmu.c
+++ b/arch/powerpc/perf/imc-pmu.c
@@ -1146,7 +1146,7 @@ static int init_nest_pmu_ref(void)
static void cleanup_all_core_imc_memory(void)
{
- int i, nr_cores = DIV_ROUND_UP(num_present_cpus(), threads_per_core);
+ int i, nr_cores = DIV_ROUND_UP(num_possible_cpus(),
threads_per_core);
struct imc_mem_info *ptr = core_imc_pmu->mem_info;
int size = core_imc_pmu->counter_mem_size;
@@ -1264,7 +1264,7 @@ static int imc_mem_init(struct imc_pmu *pmu_ptr,
struct device_node *parent,
if (!pmu_ptr->pmu.name)
return -ENOMEM;
- nr_cores = DIV_ROUND_UP(num_present_cpus(), threads_per_core);
+ nr_cores = DIV_ROUND_UP(num_possible_cpus(), threads_per_core);
pmu_ptr->mem_info = kcalloc(nr_cores, sizeof(struct
imc_mem_info),
GFP_KERNEL);
