linux-kernel - Re: ERROR: "__umoddi3" [drivers/net/ethernet/mellanox/mlx5/core/mlx5

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Date:   Tue, 15 Oct 2019 20:45:26 +0000
From:   Saeed Mahameed <saeedm@...lanox.com>
To:     "mkubecek@...e.cz" <mkubecek@...e.cz>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "stephen@...workplumber.org" <stephen@...workplumber.org>,
        Alex Vesker <valex@...lanox.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "leon@...nel.org" <leon@...nel.org>, "bp@...en8.de" <bp@...en8.de>
Subject: Re: ERROR: "__umoddi3"
 [drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.ko] undefined!

On Tue, 2019-10-15 at 20:29 +0000, Saeed Mahameed wrote:
> On Tue, 2019-10-01 at 17:14 +0200, Michal Kubecek wrote:
> > On Mon, Sep 30, 2019 at 08:40:31PM +0200, Borislav Petkov wrote:
> > > On Mon, Sep 30, 2019 at 09:55:16AM -0700, Stephen Hemminger
> > > wrote:
> > > > Could also us div_u64_rem here?
> > > 
> > > Yah, the below seems to work and the resulting asm looks sensible
> > > to me
> > > but someone should definitely double-check me as I don't know
> > > this
> > > code
> > > at all.
> > > 
> > > Thx.
> > > 
> > > diff --git
> > > a/drivers/net/ethernet/mellanox/mlx5/core/steering/dr_icm_pool.c
> > > b/drivers/net/ethernet/mellanox/mlx5/core/steering/dr_icm_pool.c
> > > index 913f1e5aaaf2..b4302658e5f8 100644
> > > ---
> > > a/drivers/net/ethernet/mellanox/mlx5/core/steering/dr_icm_pool.c
> > > +++
> > > b/drivers/net/ethernet/mellanox/mlx5/core/steering/dr_icm_pool.c
> > > @@ -137,7 +137,7 @@ dr_icm_pool_mr_create(struct mlx5dr_icm_pool
> > > *pool,
> > >  
> > >  	icm_mr->icm_start_addr = icm_mr->dm.addr;
> > >  
> > > -	align_diff = icm_mr->icm_start_addr % align_base;
> > > +	div_u64_rem(icm_mr->icm_start_addr, align_base, &align_diff);
> > >  	if (align_diff)
> > >  		icm_mr->used_length = align_base - align_diff;
> > >  
> > > 
> > 
> > While this fixes 32-bit builds, it breaks 64-bit ones as align_diff
> > is
> > 64-bit and div_u64_rem expects pointer to u32. :-(
> > 
> > I checked that align_base is always a power of two so that we could
> > get
> > away with
> > 
> > 	align_diff = icm_mr->icm_start_addr & (align_base - 1)
> > 
> > I'm not sure, however, if it's safe to assume align_base will
> > always
> > have to be a power of two or if we should add a check for safety.
> > 
> > (Cc-ing also author of commit 29cf8febd185 ("net/mlx5: DR, ICM pool
> > memory allocator").)
> > 
> 
> Thanks everyone for your input on this, Alex will take care of this
> and
> we will submit a patch ..
> 

Please disregard, i see this was fixed in 
"[net] mlx5: avoid 64-bit division in dr_icm_pool_mr_create()"

Just came back from a long vacation, got a lot of catching up to do
:)..