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[71.202.32.218]) by smtp.gmail.com with ESMTPSA id t6-20020a625f06000000b006dd87826805sm2599008pfb.75.2024.01.24.15.59.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Jan 2024 15:59:41 -0800 (PST) From: fan X-Google-Original-From: fan Date: Wed, 24 Jan 2024 15:59:08 -0800 To: Quanquan Cao Cc: dave.jiang@intel.com, vishal.l.verma@intel.com, linux-cxl@vger.kernel.org, nvdimm@lists.linux.dev Subject: Re: [PATCH] =?utf-8?B?Y3hsL3JlZ2lvbu+8mkZp?= =?utf-8?Q?x?= overflow issue in alloc_hpa() Message-ID: References: <20240124091527.8469-1-caoqq@fujitsu.com> Precedence: bulk X-Mailing-List: nvdimm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240124091527.8469-1-caoqq@fujitsu.com> On Wed, Jan 24, 2024 at 05:15:26PM +0800, Quanquan Cao wrote: > Creating a region with 16 memory devices caused a problem. The div_u64_rem > function, used for dividing an unsigned 64-bit number by a 32-bit one, > faced an issue when SZ_256M * p->interleave_ways. The result surpassed > the maximum limit of the 32-bit divisor (4G), leading to an overflow > and a remainder of 0. > note: At this point, p->interleave_ways is 16, meaning 16 * 256M = 4G > > To fix this issue, I replaced the div_u64_rem function with div64_u64_rem > and adjusted the type of the remainder. > > Signed-off-by: Quanquan Cao > --- > drivers/cxl/core/region.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c > index 0f05692bfec3..ce0e2d82bb2b 100644 > --- a/drivers/cxl/core/region.c > +++ b/drivers/cxl/core/region.c > @@ -525,7 +525,7 @@ static int alloc_hpa(struct cxl_region *cxlr, resource_size_t size) > struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(cxlr->dev.parent); > struct cxl_region_params *p = &cxlr->params; > struct resource *res; > - u32 remainder = 0; > + u64 remainder = 0; > > lockdep_assert_held_write(&cxl_region_rwsem); > > @@ -545,7 +545,7 @@ static int alloc_hpa(struct cxl_region *cxlr, resource_size_t size) > (cxlr->mode == CXL_DECODER_PMEM && uuid_is_null(&p->uuid))) > return -ENXIO; > > - div_u64_rem(size, SZ_256M * p->interleave_ways, &remainder); > + div64_u64_rem(size, (u64)SZ_256M * p->interleave_ways, &remainder); > if (remainder) > return -EINVAL; > Make sense to me. Fan > -- > 2.43.0 >