linux-kernel - Re: [PATCH v1 1/2] vdpa/mlx5: Support creating resources with uid == 0

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Date:   Tue, 1 Jun 2021 07:35:29 +0300
From:   Eli Cohen <elic@...dia.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
CC:     <jasowang@...hat.com>, <virtualization@...ts.linux-foundation.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 1/2] vdpa/mlx5: Support creating resources with uid ==
 0

On Mon, May 31, 2021 at 06:17:12PM -0400, Michael S. Tsirkin wrote:
> On Mon, May 31, 2021 at 07:04:04PM +0300, Eli Cohen wrote:
> > Currently all resources must be created with uid != 0 which is essential
> > when userspace processes are allocating virtquueue resources. Since this
> > is a kernel implementation, it is perfectly legal to open resources with
> > uid == 0.
> > 
> > In case firmware supports, avoid allocating user context.
> > 
> > Signed-off-by: Eli Cohen <elic@...dia.com>
> > ---
> > v0 --> v1:
> >   Fix typo and modify phrasing
> 
> threading's broken now

Sorry about this, will repost again.
> 
> >  drivers/vdpa/mlx5/core/resources.c | 6 ++++++
> >  include/linux/mlx5/mlx5_ifc.h      | 4 +++-
> >  2 files changed, 9 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/vdpa/mlx5/core/resources.c b/drivers/vdpa/mlx5/core/resources.c
> > index 6521cbd0f5c2..836ab9ef0fa6 100644
> > --- a/drivers/vdpa/mlx5/core/resources.c
> > +++ b/drivers/vdpa/mlx5/core/resources.c
> > @@ -54,6 +54,9 @@ static int create_uctx(struct mlx5_vdpa_dev *mvdev, u16 *uid)
> >  	void *in;
> >  	int err;
> >  
> > +	if (MLX5_CAP_GEN(mvdev->mdev, umem_uid_0))
> > +		return 0;
> > +
> >  	/* 0 means not supported */
> >  	if (!MLX5_CAP_GEN(mvdev->mdev, log_max_uctx))
> >  		return -EOPNOTSUPP;
> > @@ -79,6 +82,9 @@ static void destroy_uctx(struct mlx5_vdpa_dev *mvdev, u32 uid)
> >  	u32 out[MLX5_ST_SZ_DW(destroy_uctx_out)] = {};
> >  	u32 in[MLX5_ST_SZ_DW(destroy_uctx_in)] = {};
> >  
> > +	if (!uid)
> > +		return;
> > +
> >  	MLX5_SET(destroy_uctx_in, in, opcode, MLX5_CMD_OP_DESTROY_UCTX);
> >  	MLX5_SET(destroy_uctx_in, in, uid, uid);
> >  
> > diff --git a/include/linux/mlx5/mlx5_ifc.h b/include/linux/mlx5/mlx5_ifc.h
> > index 9c68b2da14c6..606d2aeacad4 100644
> > --- a/include/linux/mlx5/mlx5_ifc.h
> > +++ b/include/linux/mlx5/mlx5_ifc.h
> > @@ -1487,7 +1487,9 @@ struct mlx5_ifc_cmd_hca_cap_bits {
> >  	u8         uar_4k[0x1];
> >  	u8         reserved_at_241[0x9];
> >  	u8         uar_sz[0x6];
> > -	u8         reserved_at_250[0x8];
> > +	u8         reserved_at_248[0x2];
> > +	u8         umem_uid_0[0x1];
> > +	u8         reserved_at_250[0x5];
> >  	u8         log_pg_sz[0x8];
> >  
> >  	u8         bf[0x1];
> > -- 
> > 2.31.1
>