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Tue, 10 Jun 2025 08:14:04 GMT Received: from smtpav04.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C3F9C58045; Tue, 10 Jun 2025 08:14:04 +0000 (GMT) Received: from smtpav04.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id DF79D58054; Tue, 10 Jun 2025 08:14:02 +0000 (GMT) Received: from [9.109.245.113] (unknown [9.109.245.113]) by smtpav04.wdc07v.mail.ibm.com (Postfix) with ESMTP; Tue, 10 Jun 2025 08:14:02 +0000 (GMT) Message-ID: <0b9e1e55-f4c9-4e30-abe6-3b9765ba9ebf@linux.ibm.com> Date: Tue, 10 Jun 2025 13:44:01 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/memory-tier: Fix abstract distance calculation overflow To: Li Zhijian , linux-mm@kvack.org Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Ying Huang References: <20250610062751.2365436-1-lizhijian@fujitsu.com> Content-Language: en-US From: Donet Tom In-Reply-To: <20250610062751.2365436-1-lizhijian@fujitsu.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: xmceErOpFt8yCePtbSQsA-WmXVmkl-pq X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNjEwMDA1OCBTYWx0ZWRfX1TK7gdleShsC ZlZL227d1dnBeXmMwCzS2BZrqqKeM+XQP9A/2KYiK6yJeQHfb6f9h3Qd2L29Smg1FG3oO/sLUi7 XdZgarrGFWP0CO7BZ0mLnVsmjYHH1VuXd0KsecD4KPoY4pBM6PtJNUq8LsiGopra3ZvWZme0SAA pg/X4UE6gFIRhawMLExLl5XyHPnxmNFrEiLh+dXZGwHcMFwgkgVyi1Cb9J8GAp4YkThLoV1DzqD /XljKsKhI+MifNstt2oQmV/LpcwpbpUvQG/LfJuSS2TGK1lyuwULWxvb3KQcFy8UKRir0xtkZkY 6SiWRB1xJntae2+7d6HMjGzXitp356xZWfEovwh7U9uk7gVxXAqkSu62o1aUZCppeV8DIdFWhGS 6emig6fwRqAMbtLKq1hGCp/dKzyHOvbw3xjnrROQ+AR7rusllOd6uvJoxSpCMfZI13vzFZ3k X-Authority-Analysis: v=2.4 cv=YKGfyQGx c=1 sm=1 tr=0 ts=6847e94e cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=6IFa9wvqVegA:10 a=pGLkceISAAAA:8 a=omOdbC7AAAAA:8 a=VnNF1IyMAAAA:8 a=MjiR9eHTnMDsPQ3Rr7EA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: hLWlauVIk4vxWRo7QYfEL2eAP_IZVkSd X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-06-10_02,2025-06-09_02,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 clxscore=1011 malwarescore=0 bulkscore=0 priorityscore=1501 phishscore=0 mlxscore=0 lowpriorityscore=0 impostorscore=0 adultscore=0 mlxlogscore=999 suspectscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505280000 definitions=main-2506100058 On 6/10/25 11:57 AM, Li Zhijian wrote: > In mt_perf_to_adistance(), the calculation of abstract distance (adist) > involves multiplying several int values including MEMTIER_ADISTANCE_DRAM. > ``` > *adist = MEMTIER_ADISTANCE_DRAM * > (perf->read_latency + perf->write_latency) / > (default_dram_perf.read_latency + default_dram_perf.write_latency) * > (default_dram_perf.read_bandwidth + default_dram_perf.write_bandwidth) / > (perf->read_bandwidth + perf->write_bandwidth); > ``` > Since these values can be large, the multiplication may exceed the maximum > value of an int (INT_MAX) and overflow (Our platform did), leading to an > incorrect adist. > > Change MEMTIER_ADISTANCE_DRAM to be a long constant by writing it with the > 'L' suffix. This prevents the overflow because the multiplication will then > be done in the long type which has a larger range. > > Fixes: 3718c02dbd4c ("acpi, hmat: calculate abstract distance with HMAT") > Cc: Ying Huang > Signed-off-by: Li Zhijian > --- > include/linux/memory-tiers.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h > index 0dc0cf2863e2..7a805796fcfd 100644 > --- a/include/linux/memory-tiers.h > +++ b/include/linux/memory-tiers.h > @@ -18,7 +18,7 @@ > * adistance value (slightly faster) than default DRAM adistance to be part of > * the same memory tier. > */ > -#define MEMTIER_ADISTANCE_DRAM ((4 * MEMTIER_CHUNK_SIZE) + (MEMTIER_CHUNK_SIZE >> 1)) > +#define MEMTIER_ADISTANCE_DRAM ((4L * MEMTIER_CHUNK_SIZE) + (MEMTIER_CHUNK_SIZE >> 1)) Hi Li Zhijian This looks good to me. Feel free to add Reviewed-byDonet Tom > > struct memory_tier; > struct memory_dev_type {