Re: [RFC net-next 5/7] net/ism: Move ism_loopback to net/ism

Julian Ruess
2025-02-06T17:36:30Z

On Wed Jan 15, 2025 at 8:55 PM CET, Alexandra Winter wrote:
> The first stage of ism_loopback was implemented as part of the
> SMC module [1]. Now that we have the ism layer, provide
> access to the ism_loopback device to all ism clients.
>
> Move ism_loopback.* from net/smc to net/ism.
> The following changes are required to ism_loopback.c:
> - Change ism_lo_move_data() to no longer schedule an smcd receive tasklet,
> but instead call ism_client->handle_irq().
> Note: In this RFC patch ism_loppback is not fully generic.
> The smc-d client uses attached buffers, for moves without signalling.
> and not-attached buffers for moves with signalling.
> ism_lo_move_data() must not rely on that assumption.
> ism_lo_move_data() must be able to handle more than one ism client.
>
> In addition the following changes are required to unify ism_loopback and
> ism_vp:
>
> In ism layer and ism_vpci:
> ism_loopback is not backed by a pci device, so use dev instead of pdev in
> ism_dev.
>
> In smc-d:
> in smcd_alloc_dev():
> - use kernel memory instead of device memory for smcd_dev and smcd->conn.
> An alternative would be to ask device to alloc the memory.
> - use different smcd_ops and max_dmbs for ism_vp and ism_loopback.
> A future patch can change smc-d to directly use ism_ops instead of
> smcd_ops.
> - use ism dev_name instead of pci dev name for ism_evt_wq name
> - allocate an event workqueue for ism_loopback, although it currently does
> not generate events.
>
> Link: https://lore.kernel.org/linux-kernel//20240428060738.60843-1-guwen@linux.alibaba.com/ [1]
>
> Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>
> ---
> drivers/s390/net/ism.h | 6 +-
> drivers/s390/net/ism_drv.c | 31 ++-
> include/linux/ism.h | 59 +++++
> include/net/smc.h | 4 +-
> net/ism/Kconfig | 13 ++
> net/ism/Makefile | 1 +
> net/ism/ism_loopback.c | 366 +++++++++++++++++++++++++++++++
> net/ism/ism_loopback.h | 59 +++++
> net/ism/ism_main.c | 11 +-
> net/smc/Kconfig | 13 --
> net/smc/Makefile | 1 -
> net/smc/af_smc.c | 12 +-
> net/smc/smc_ism.c | 108 +++++++---
> net/smc/smc_loopback.c | 427 -------------------------------------
> net/smc/smc_loopback.h | 60 ------
> 15 files changed, 606 insertions(+), 565 deletions(-)
> create mode 100644 net/ism/ism_loopback.c
> create mode 100644 net/ism/ism_loopback.h
> delete mode 100644 net/smc/smc_loopback.c
> delete mode 100644 net/smc/smc_loopback.h
>

...

> diff --git a/net/ism/ism_loopback.c b/net/ism/ism_loopback.c
> new file mode 100644
> index 000000000000..47e5ef355dd7
> --- /dev/null
> +++ b/net/ism/ism_loopback.c
> @@ -0,0 +1,366 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Functions for loopback-ism device.
> + *
> + * Copyright (c) 2024, Alibaba Inc.
> + *
> + * Author: Wen Gu <guwen@linux.alibaba.com>
> + * Tony Lu <tonylu@linux.alibaba.com>
> + *
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/device.h>
> +#include <linux/ism.h>
> +#include <linux/spinlock.h>
> +#include <linux/types.h>
> +
> +#include "ism_loopback.h"
> +
> +#define ISM_LO_V2_CAPABLE 0x1 /* loopback-ism acts as ISMv2 */
> +#define ISM_LO_SUPPORT_NOCOPY 0x1
> +#define ISM_DMA_ADDR_INVALID (~(dma_addr_t)0)
> +
> +static const char ism_lo_dev_name[] = "loopback-ism";
> +/* global loopback device */
> +static struct ism_lo_dev *lo_dev;
> +
> +static int ism_lo_query_rgid(struct ism_dev *ism, uuid_t *rgid,
> + u32 vid_valid, u32 vid)
> +{
> + /* rgid should be the same as lgid; vlan is not supported */
> + if (!vid_valid && uuid_equal(rgid, &ism->gid))
> + return 0;
> + return -ENETUNREACH;
> +}

This vid_valid check breaks ism-loopback for me.