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

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Message-ID: <20210531045814.GA158940@mtl-vdi-166.wap.labs.mlnx>
Date:   Mon, 31 May 2021 07:58:14 +0300
From:   Eli Cohen <elic@...dia.com>
To:     Jason Wang <jasowang@...hat.com>
CC:     <mst@...hat.com>, <virtualization@...ts.linux-foundation.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] vdpa/mlx5: Support creating resources with uid == 0

On Mon, May 31, 2021 at 11:02:21AM +0800, Jason Wang wrote:
> 
> 在 2021/5/30 下午3:54, Eli Cohen 写道:
> > Currently all resources must be created with uid != 0 which is essential
> > userspace processes allocating virtquueue resources. Since this is a
> > kernel implementation, it is perfectly legal to open resources with
> > uid == 0.
> > 
> > In case frimware supports, avoid allocating user context.
> 
> 
> Typo "frimware".
> 
> Otherwise.
> 
> Acked-by: Jason Wang <jasowang@...hat.com>
> 
> (I don't see any code to check the firmware capability, is this intended?)
> 
> Thanks
> 
> 
> > 
> > Signed-off-by: Eli Cohen <elic@...dia.com>
> > ---
> >   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;
> > +

This checks that the "umem_uid_0" capability is set. If it is set, then
I don't create the user context which will result in uid being zero.

> >   	/* 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];
>