Messages in this thread | | | From | Petr Machata <> | Subject | Re: [PATCH] mlxsw: spectrum_qdisc: Fix 64-bit division error in mlxsw_sp_qdisc_tbf_rate_kbps | Date | Mon, 03 Feb 2020 11:03:42 +0100 |
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Nathan Chancellor <natechancellor@gmail.com> writes:
> On Thu, Jan 30, 2020 at 05:43:56PM -0800, Randy Dunlap wrote: >> On 1/30/20 3:26 PM, Nathan Chancellor wrote: >> > When building arm32 allmodconfig: >> > >> > ERROR: "__aeabi_uldivmod" >> > [drivers/net/ethernet/mellanox/mlxsw/mlxsw_spectrum.ko] undefined! >> > >> > rate_bytes_ps has type u64, we need to use a 64-bit division helper to >> > avoid a build error. >> > >> > Fixes: a44f58c41bfb ("mlxsw: spectrum_qdisc: Support offloading of TBF Qdisc") >> > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> >> > --- >> > drivers/net/ethernet/mellanox/mlxsw/spectrum_qdisc.c | 2 +- >> > 1 file changed, 1 insertion(+), 1 deletion(-) >> > >> > diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_qdisc.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_qdisc.c >> > index 79a2801d59f6..65e681ef01e8 100644 >> > --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_qdisc.c >> > +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_qdisc.c >> > @@ -614,7 +614,7 @@ mlxsw_sp_qdisc_tbf_rate_kbps(struct tc_tbf_qopt_offload_replace_params *p) >> > /* TBF interface is in bytes/s, whereas Spectrum ASIC is configured in >> > * Kbits/s. >> > */ >> > - return p->rate.rate_bytes_ps / 1000 * 8; >> > + return div_u64(p->rate.rate_bytes_ps, 1000 * 8); >> >> not quite right AFAICT. >> >> try either >> return div_u64(p->rate.rate_bytes_ps * 8, 1000); >> or >> return div_u64(p->rate.rate_bytes_ps, 1000) * 8; >> > > Gah, I swear I can math... Thank you for catching this, v2 incoming with > the later because I think it looks better.
Yes, that's the correct choice. Divide first, that way we can't overflow.
Thanks for taking care of this.
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