Re: [PATCH v3 1/2] RDMA/rxe: Reject IB_ACCESS_ON_DEMAND changes after MR creation

[Zhu Yanjun]

在 2026/9/23 7:40, Norbert Szetei via B4 Relay 写道:
> From: Norbert Szetei <norbert@xxxxxxxxxxxx>
>
> Whether an MR is an ODP MR is decided once, at registration time:
> rxe_reg_user_mr() picks rxe_odp_mr_init_user() over rxe_mr_init_user()
> based on IB_ACCESS_ON_DEMAND, and only the former builds an ib_umem_odp
> via ib_umem_odp_get(). The umem cannot change type afterwards, and
> is_odp_mr() reads mr->umem->is_odp.
>
> Two paths assign mr->access after that point and can leave it
> describing an MR type the umem does not have:
>
> rxe_rereg_user_mr() with IB_MR_REREG_ACCESS overwrites mr->access with
> the caller's value, and IB_ACCESS_ON_DEMAND is part of
> RXE_ACCESS_SUPPORTED_MR, so userspace can set the flag on a plain MR or
> clear it on an ODP MR while the umem stays what it was.
>
> rxe_reg_fast_mr() takes mr->access from the REG_MR work request
> unmasked and moves the MR to RXE_MR_STATE_VALID, on an MR that
> rxe_mr_init_fast() left with a NULL umem.
>
> Reject IB_ACCESS_ON_DEMAND in both, so mr->access carries the flag only
> for an MR that has an ODP umem and the flag can be used to identify one.
>
> Fixes: 544c7f62cf32 ("RDMA/rxe: Implement rereg_user_mr")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Norbert Szetei <norbert@xxxxxxxxxxxx>

I have already reviewed this commit. I am fine with this commit.
So
Reviewed-by: Zhu Yanjun <yanjun.zhu@xxxxxxxxx>

Zhu Yanjun

> ---
>   drivers/infiniband/sw/rxe/rxe_mr.c    | 6 ++++++
>   drivers/infiniband/sw/rxe/rxe_verbs.c | 6 ++++++
>   2 files changed, 12 insertions(+)
>
> diff --git a/drivers/infiniband/sw/rxe/rxe_mr.c b/drivers/infiniband/sw/rxe/rxe_mr.c
> index 875eceb55fdf..2afda5154dfb 100644
> --- a/drivers/infiniband/sw/rxe/rxe_mr.c
> +++ b/drivers/infiniband/sw/rxe/rxe_mr.c
> @@ -795,6 +795,12 @@ int rxe_reg_fast_mr(struct rxe_qp *qp, struct rxe_send_wqe *wqe)
>   		return -EINVAL;
>   	}
>   
> +	/* an MR with no umem is never an ODP MR */
> +	if (unlikely(access & IB_ACCESS_ON_DEMAND)) {
> +		rxe_dbg_mr(mr, "access = 0x%x requests ODP\n", access);
> +		return -EINVAL;
> +	}
> +
>   	mr->access = access;
>   	mr->lkey = key;
>   	mr->rkey = key;
> diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.c b/drivers/infiniband/sw/rxe/rxe_verbs.c
> index 96c7716057fe..21855274f63a 100644
> --- a/drivers/infiniband/sw/rxe/rxe_verbs.c
> +++ b/drivers/infiniband/sw/rxe/rxe_verbs.c
> @@ -1331,6 +1331,12 @@ static struct ib_mr *rxe_rereg_user_mr(struct ib_mr *ibmr, int flags,
>   	if (err)
>   		return ERR_PTR(err);
>   
> +	if ((flags & IB_MR_REREG_ACCESS) &&
> +	    ((access ^ mr->access) & IB_ACCESS_ON_DEMAND)) {
> +		rxe_err_mr(mr, "cannot change IB_ACCESS_ON_DEMAND\n");
> +		return ERR_PTR(-EOPNOTSUPP);
> +	}
> +
>   	if (flags & IB_MR_REREG_PD) {
>   		rxe_put(old_pd);
>   		rxe_get(pd);