linux-kernel - Re: [PATCH rdma] IB/mlx5: Fix linkage failure on 32-bit arches

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Date:   Sun, 16 Feb 2020 13:53:50 +0200
From:   Maxim Mikityanskiy <maximmi@...lanox.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     Alexander Lobakin <alobakin@...nk.ru>,
        Leon Romanovsky <leon@...nel.org>,
        Doug Ledford <dledford@...hat.com>,
        Yishai Hadas <yishaih@...lanox.com>,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH rdma] IB/mlx5: Fix linkage failure on 32-bit arches

On 2020-02-14 21:44, Alexander Lobakin wrote:
> Jason Gunthorpe wrote 14.02.2020 22:24:
>> On Fri, Feb 14, 2020 at 10:13:09PM +0300, Alexander Lobakin wrote:
>>> Commit f164be8c0366 ("IB/mlx5: Extend caps stage to handle VAR
>>> capabilities") introduced a straight "/" division of the u64
>>> variable "bar_size", which emits an __udivdi3() libgcc call on
>>> 32-bit arches and certain GCC versions:
>>>
>>> error: "__udivdi3" [drivers/infiniband/hw/mlx5/mlx5_ib.ko] undefined! 
>>> [1]
>>>
>>> Replace it with the corresponding div_u64() call.
>>> Compile-tested on ARCH=mips 32r2el_defconfig BOARDS=ocelot.
>>>
>>> [1] 
>>> https://lore.kernel.org/linux-mips/CAMuHMdXM9S1VkFMZ8eDAyZR6EE4WkJY215Lcn2qdOaPeadF+EQ@mail.gmail.com/ 
>>>
>>>
>>> Fixes: f164be8c0366 ("IB/mlx5: Extend caps stage to handle VAR
>>> capabilities")
>>> Signed-off-by: Alexander Lobakin <alobakin@...nk.ru>
>>> ---
>>>  drivers/infiniband/hw/mlx5/main.c | 3 ++-
>>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> Randy beat you too it..
>>
>> https://lore.kernel.org/linux-rdma/20200206143201.GF25297@ziepe.ca/
> 
> Ah, OK. Sorry for missing this one. I didn't see any fix over
> git.kernel.org and thought it doesn't exist yet.
> 
>> But it seems patchwork missed this somehow.
>>
>> Applied now at least

Jason, I think Alexander's patch is more correct. It uses div_u64, while 
yours uses div64_u64. The divider is 32-bit, so div_u64 would be more 
optimized on most 32-bit architectures.

> Thanks!
> 
>> Jason
> 
> Regards,
> ᚷ ᛖ ᚢ ᚦ ᚠ ᚱ