Re: [v2,net-next,1/6] net: mana: Create separate EQs for each vPort

[Simon Horman <horms@kernel.org>]

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---
net: mana: Create separate EQs for each vPort

To prepare for assigning vPorts to dedicated MSI-X vectors, this commit
removes EQ sharing among vPorts and creates dedicated EQs for each vPort.
The EQ definition is moved from struct mana_context to struct
mana_port_context and related support functions are updated.

> diff --git a/include/net/mana/mana.h b/include/net/mana/mana.h
> --- a/include/net/mana/mana.h
> +++ b/include/net/mana/mana.h

[ ... ]

> @@ -499,6 +497,9 @@ struct mana_port_context {
>
>  	u8 mac_addr[ETH_ALEN];
>
> +	struct mana_eq *eqs;
> +	struct dentry *mana_eqs_debugfs;
> +
>  	enum TRI_STATE rss_state;
>
>  	mana_handle_t default_rxobj;

[ ... ]

> diff --git a/drivers/infiniband/hw/mana/qp.c b/drivers/infiniband/hw/mana/qp.c
> --- a/drivers/infiniband/hw/mana/qp.c
> +++ b/drivers/infiniband/hw/mana/qp.c
> @@ -188,7 +188,7 @@ struct mana_obj_spec cq_spec = {};
>  		cq_spec.gdma_region = cq->queue.gdma_region;
>  		cq_spec.queue_size = cq->cqe * COMP_ENTRY_SIZE;
>  		cq_spec.modr_ctx_id = 0;
> -		eq = &mpc->ac->eqs[cq->comp_vector];
> +		eq = &mpc->eqs[cq->comp_vector % mpc->num_queues];
                           ^^^^^^^
>  		cq_spec.attached_eq = eq->eq->id;

Can mpc->eqs be NULL here? Looking at the initialization paths:

Before this patch, mpc->ac->eqs was allocated during mana_probe() and was
always non-NULL after driver initialization.

After this patch, mpc->eqs is only allocated in two places:
1. mana_alloc_queues() - called when the Ethernet interface is brought up
2. mana_ib_cfg_vport() - called when RDMA RAW QPs configure the vport

However, mana_ib_create_qp_rss() doesn't call mana_ib_cfg_vport(). If an
RSS QP is created via RDMA verbs before the Ethernet port is brought up
and before any RAW QP has configured the vport, mpc->eqs would still be
NULL.

Computing &mpc->eqs[cq->comp_vector % mpc->num_queues] from a NULL pointer
produces an invalid address, and the subsequent dereference eq->eq->id
would crash the kernel.

Should there be a NULL check here, or should mana_ib_create_qp_rss()
ensure EQs are created before reaching this point?

>
>  		ret = mana_create_wq_obj(mpc, mpc->port_handle, GDMA_RQ,

[ ... ]