From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 40m4gY261lzF1f4 for ; Wed, 16 May 2018 16:45:13 +1000 (AEST) Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w4G6jAm2077790 for ; Wed, 16 May 2018 02:45:10 -0400 Received: from e33.co.us.ibm.com (e33.co.us.ibm.com [32.97.110.151]) by mx0a-001b2d01.pphosted.com with ESMTP id 2j0fgurb23-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 16 May 2018 02:45:09 -0400 Received: from localhost by e33.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 16 May 2018 00:45:02 -0600 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Date: Wed, 16 May 2018 12:18:18 +0530 From: ppaidipe To: Anju T Sudhakar Cc: mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org, maddy@linux.vnet.ibm.com, bsingharora@gmail.com Subject: Re: [PATCH v2] powerpc/perf: Fix memory allocation for core-imc based on num_possible_cpus() In-Reply-To: <1526452518-12611-1-git-send-email-anju@linux.vnet.ibm.com> References: <1526452518-12611-1-git-send-email-anju@linux.vnet.ibm.com> Message-Id: <0df1478ff69b9e2f2c70897a472ada39@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 > Signed-off-by: Anju T Sudhakar > Reviewed-by: Balbir Singh 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 > --- > 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);