From: "Cao, Quanquan/曹 全全" <caoqq@fujitsu.com>
To: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
Cc: dave.jiang@intel.com, vishal.l.verma@intel.com,
linux-cxl@vger.kernel.org, nvdimm@lists.linux.dev
Subject: Re: [PATCH] cxl/region:Fix overflow issue in alloc_hpa()
Date: Mon, 29 Jan 2024 10:22:08 +0800 [thread overview]
Message-ID: <64d4a375-ddca-18bf-8532-f730632534b7@fujitsu.com> (raw)
In-Reply-To: <20240126174223.00005736@Huawei.com>
在 2024/1/27 1:42, Jonathan Cameron 写道:
> On Wed, 24 Jan 2024 17:15:26 +0800
> Quanquan Cao <caoqq@fujitsu.com> 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 <caoqq@fujitsu.com>
> Good find, though now I'm curious on whether you have a real system doing
> 16 way interleave :)
Yes, currently the specification is 8, and 16 will be the maximum value.
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>> ---
>> 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;
>>
>
next prev parent reply other threads:[~2024-01-29 2:22 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-24 9:15 [PATCH] cxl/region:Fix overflow issue in alloc_hpa() Quanquan Cao
2024-01-24 23:59 ` fan
2024-01-25 0:02 ` Dave Jiang
2024-01-26 17:42 ` Jonathan Cameron
2024-01-29 2:22 ` Cao, Quanquan/曹 全全 [this message]
2024-01-26 21:47 ` Alison Schofield
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