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 3yLmmN0Dj6zDqZ3 for ; Tue, 24 Oct 2017 19:34:59 +1100 (AEDT) Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v9O8Ycw0136620 for ; Tue, 24 Oct 2017 04:34:57 -0400 Received: from e37.co.us.ibm.com (e37.co.us.ibm.com [32.97.110.158]) by mx0b-001b2d01.pphosted.com with ESMTP id 2dt0dhey0m-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Tue, 24 Oct 2017 04:34:56 -0400 Received: from localhost by e37.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 24 Oct 2017 02:34:55 -0600 Subject: Re: [PATCH] powerpc/perf: Fix IMC allocation routine To: "Guilherme G. Piccoli" , linuxppc-dev@lists.ozlabs.org Cc: benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au References: <20171019194133.27485-1-gpiccoli@linux.vnet.ibm.com> From: Anju T Sudhakar Date: Tue, 24 Oct 2017 14:04:49 +0530 MIME-Version: 1.0 In-Reply-To: <20171019194133.27485-1-gpiccoli@linux.vnet.ibm.com> Content-Type: multipart/alternative; boundary="------------E6405BBCE3DBD5FE87689334" Message-Id: <5d035de1-309b-3b3c-bbcb-9e28ae9422e3@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , This is a multi-part message in MIME format. --------------E6405BBCE3DBD5FE87689334 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit 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 Acked-by:  Anju T Sudhakar > --- > 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 --------------E6405BBCE3DBD5FE87689334 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: 8bit

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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