Re: [dpdk-dev] [PATCH] net/mlx5: fix left shift extension of doorbell bitmap

[Raslan Darawsheh <rasland@mellanox.com>]

> -----Original Message-----
> From: Raslan Darawsheh
> Sent: Sunday, May 17, 2020 12:19 PM
> To: Bing Zhao <bingz@mellanox.com>; Slava Ovsiienko
> <viacheslavo@mellanox.com>
> Cc: Ori Kam <orika@mellanox.com>; Matan Azrad <matan@mellanox.com>;
> dev@dpdk.org; stable@dpdk.org; Dekel Peled <dekelp@mellanox.com>
> Subject: RE: [PATCH] net/mlx5: fix left shift extension of doorbell bitmap
> 
> Hi,
> 
> > -----Original Message-----
> > From: Bing Zhao <bingz@mellanox.com>
> > Sent: Friday, May 15, 2020 11:14 AM
> > To: Slava Ovsiienko <viacheslavo@mellanox.com>; Raslan Darawsheh
> > <rasland@mellanox.com>
> > Cc: Ori Kam <orika@mellanox.com>; Matan Azrad
> <matan@mellanox.com>;
> > dev@dpdk.org; stable@dpdk.org; Dekel Peled <dekelp@mellanox.com>
> > Subject: [PATCH] net/mlx5: fix left shift extension of doorbell bitmap
> >
> > The doorbell record is organized with page and bitmap. When some new
> > doorbell needs to be associated with a queue, the bit will be set
> > in the bitmap to indicate the corresponding doorbell occupied. A
> > counter is used to record the number of doorbell occupied to speed
> > up the searching.
> > If the number reachs the maximal value of a pre-defined number of a
> > page, a new page will be allocated. If not, then the bitmap will be
> > checked to find a free one.
> > The LSHIFT and OR (AND NOT) operations are used to update the bitmap
> > of a page. But 1 will be treated as a signed integer when compiling.
> > When the shift number is 31, the shifted value will be considered as
> > negative. Then a wrong extension will be done when setting it to a
> > 64-bits variable. All the upper 32-bits will be set to 1 by such
> > extension.
> > Then a wrong offset value will be calculated because of this. The
> > next 64 bits will be also treated as the bitmap and get corrupted
> > through the bit set operation.
> > The immediate value 1 needs to be used as 64 bits width explicitly.
> >
> > Fixes: 21cae8580fd0 ("net/mlx5: allocate door-bells via DevX")
> > Cc: dekelp@mellanox.com
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Bing Zhao <bingz@mellanox.com>
> > Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
> > ---
> >  drivers/net/mlx5/mlx5.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/mlx5/mlx5.c b/drivers/net/mlx5/mlx5.c
> > index 1445809..ab4adec 100644
> > --- a/drivers/net/mlx5/mlx5.c
> > +++ b/drivers/net/mlx5/mlx5.c
> > @@ -2174,7 +2174,7 @@ struct mlx5_flow_id_pool *
> >  	/* Find the first clear bit. */
> >  	MLX5_ASSERT(i < MLX5_DBR_BITMAP_SIZE);
> >  	j = rte_bsf64(~page->dbr_bitmap[i]);
> > -	page->dbr_bitmap[i] |= (1 << j);
> > +	page->dbr_bitmap[i] |= (UINT64_C(1) << j);
> >  	page->dbr_count++;
> >  	*dbr_page = page;
> >  	return (((i * 64) + j) * sizeof(uint64_t));
> > @@ -2219,7 +2219,7 @@ struct mlx5_flow_id_pool *
> >  		int i = offset / 64;
> >  		int j = offset % 64;
> >
> > -		page->dbr_bitmap[i] &= ~(1 << j);
> > +		page->dbr_bitmap[i] &= ~(UINT64_C(1) << j);
> >  	}
> >  	return ret;
> >  }
> > --
> > 1.8.3.1
> 
> Commit title changed to:
> net/mlx5: fix left shift extension of doorbell bitmap
Commit title sent incorrectly, the fix title is:
net/mlx5: fix doorbell bitmap management offsets

> 
> Patch applied to next-net-mlx,
> 
> Kindest regards
> Raslan Darawsheh
Kindest regards
Raslan Darawsheh