Re: [PATCH v3 for-next 07/16] IB/ipoib: Increase ipoib Datagram mode MTU's upper limit

[Nathan Chancellor <natechancellor@gmail.com>]

On Mon, May 11, 2020 at 12:06:18PM -0400, Dennis Dalessandro wrote:
> From: Kaike Wan <kaike.wan@intel.com>
> 
> Currently the ipoib UD mtu is restricted to 4K bytes. Remove this
> limitation so that the IPOIB module can potentially use an MTU (in UD
> mode) that is bounded by the MTU of the underlying device. A field is
> added to the ib_port_attr structure to indicate the maximum physical
> MTU the underlying device supports.
> 
> Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
> Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
> Signed-off-by: Sadanand Warrier <sadanand.warrier@intel.com>
> Signed-off-by: Kaike Wan <kaike.wan@intel.com>
> Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
> ---
>  drivers/infiniband/hw/hfi1/qp.c                |   18 +-----
>  drivers/infiniband/hw/hfi1/verbs.c             |    2 +
>  drivers/infiniband/ulp/ipoib/ipoib_main.c      |    2 -
>  drivers/infiniband/ulp/ipoib/ipoib_multicast.c |   11 ++-
>  include/rdma/ib_verbs.h                        |   77 ++++++++++++++++++++++++
>  include/rdma/opa_port_info.h                   |   10 ---
>  6 files changed, 88 insertions(+), 32 deletions(-)
> 
> diff --git a/drivers/infiniband/hw/hfi1/qp.c b/drivers/infiniband/hw/hfi1/qp.c
> index f8e733a..0c2ae9f 100644
> --- a/drivers/infiniband/hw/hfi1/qp.c
> +++ b/drivers/infiniband/hw/hfi1/qp.c
> @@ -1,5 +1,5 @@
>  /*
> - * Copyright(c) 2015 - 2019 Intel Corporation.
> + * Copyright(c) 2015 - 2020 Intel Corporation.
>   *
>   * This file is provided under a dual BSD/GPLv2 license.  When using or
>   * redistributing this file, you may do so under either license.
> @@ -186,15 +186,6 @@ static void flush_iowait(struct rvt_qp *qp)
>  	write_sequnlock_irqrestore(lock, flags);
>  }
>  
> -static inline int opa_mtu_enum_to_int(int mtu)
> -{
> -	switch (mtu) {
> -	case OPA_MTU_8192:  return 8192;
> -	case OPA_MTU_10240: return 10240;
> -	default:            return -1;
> -	}
> -}
> -
>  /**
>   * This function is what we would push to the core layer if we wanted to be a
>   * "first class citizen".  Instead we hide this here and rely on Verbs ULPs
> @@ -202,15 +193,10 @@ static inline int opa_mtu_enum_to_int(int mtu)
>   */
>  static inline int verbs_mtu_enum_to_int(struct ib_device *dev, enum ib_mtu mtu)
>  {
> -	int val;
> -
>  	/* Constraining 10KB packets to 8KB packets */
>  	if (mtu == (enum ib_mtu)OPA_MTU_10240)
>  		mtu = OPA_MTU_8192;
> -	val = opa_mtu_enum_to_int((int)mtu);
> -	if (val > 0)
> -		return val;
> -	return ib_mtu_enum_to_int(mtu);
> +	return opa_mtu_enum_to_int((enum opa_mtu)mtu);
>  }
>  
>  int hfi1_check_modify_qp(struct rvt_qp *qp, struct ib_qp_attr *attr,
> diff --git a/drivers/infiniband/hw/hfi1/verbs.c b/drivers/infiniband/hw/hfi1/verbs.c
> index c61b291..19d5d00 100644
> --- a/drivers/infiniband/hw/hfi1/verbs.c
> +++ b/drivers/infiniband/hw/hfi1/verbs.c
> @@ -1439,6 +1439,8 @@ static int query_port(struct rvt_dev_info *rdi, u8 port_num,
>  				      4096 : hfi1_max_mtu), IB_MTU_4096);
>  	props->active_mtu = !valid_ib_mtu(ppd->ibmtu) ? props->max_mtu :
>  		mtu_to_enum(ppd->ibmtu, IB_MTU_4096);
> +	props->phys_mtu = HFI1_CAP_IS_KSET(AIP) ? hfi1_max_mtu :
> +				ib_mtu_enum_to_int(props->max_mtu);
>  
>  	return 0;
>  }
> diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c b/drivers/infiniband/ulp/ipoib/ipoib_main.c
> index d4c6a97..22216f1 100644
> --- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
> +++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
> @@ -1855,7 +1855,7 @@ static int ipoib_parent_init(struct net_device *ndev)
>  			priv->port);
>  		return result;
>  	}
> -	priv->max_ib_mtu = ib_mtu_enum_to_int(attr.max_mtu);
> +	priv->max_ib_mtu = rdma_mtu_from_attr(priv->ca, priv->port, &attr);
>  
>  	result = ib_query_pkey(priv->ca, priv->port, 0, &priv->pkey);
>  	if (result) {
> diff --git a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
> index b9e9562..7166ee9b 100644
> --- a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
> +++ b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
> @@ -218,6 +218,7 @@ static int ipoib_mcast_join_finish(struct ipoib_mcast *mcast,
>  	struct rdma_ah_attr av;
>  	int ret;
>  	int set_qkey = 0;
> +	int mtu;
>  
>  	mcast->mcmember = *mcmember;
>  
> @@ -240,13 +241,11 @@ static int ipoib_mcast_join_finish(struct ipoib_mcast *mcast,
>  		priv->broadcast->mcmember.flow_label = mcmember->flow_label;
>  		priv->broadcast->mcmember.hop_limit = mcmember->hop_limit;
>  		/* assume if the admin and the mcast are the same both can be changed */
> +		mtu = rdma_mtu_enum_to_int(priv->ca,  priv->port,
> +					   priv->broadcast->mcmember.mtu);
>  		if (priv->mcast_mtu == priv->admin_mtu)
> -			priv->admin_mtu =
> -			priv->mcast_mtu =
> -			IPOIB_UD_MTU(ib_mtu_enum_to_int(priv->broadcast->mcmember.mtu));
> -		else
> -			priv->mcast_mtu =
> -			IPOIB_UD_MTU(ib_mtu_enum_to_int(priv->broadcast->mcmember.mtu));
> +			priv->admin_mtu = IPOIB_UD_MTU(mtu);
> +		priv->mcast_mtu = IPOIB_UD_MTU(mtu);
>  
>  		priv->qkey = be32_to_cpu(priv->broadcast->mcmember.qkey);
>  		spin_unlock_irq(&priv->lock);
> diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
> index 4b23ee5..792fb72 100644
> --- a/include/rdma/ib_verbs.h
> +++ b/include/rdma/ib_verbs.h
> @@ -462,6 +462,11 @@ enum ib_mtu {
>  	IB_MTU_4096 = 5
>  };
>  
> +enum opa_mtu {
> +	OPA_MTU_8192 = 6,
> +	OPA_MTU_10240 = 7
> +};
> +
>  static inline int ib_mtu_enum_to_int(enum ib_mtu mtu)
>  {
>  	switch (mtu) {
> @@ -488,6 +493,28 @@ static inline enum ib_mtu ib_mtu_int_to_enum(int mtu)
>  		return IB_MTU_256;
>  }
>  
> +static inline int opa_mtu_enum_to_int(enum opa_mtu mtu)
> +{
> +	switch (mtu) {
> +	case OPA_MTU_8192:
> +		return 8192;
> +	case OPA_MTU_10240:
> +		return 10240;
> +	default:
> +		return(ib_mtu_enum_to_int((enum ib_mtu)mtu));
> +	}
> +}
> +
> +static inline enum opa_mtu opa_mtu_int_to_enum(int mtu)
> +{
> +	if (mtu >= 10240)
> +		return OPA_MTU_10240;
> +	else if (mtu >= 8192)
> +		return OPA_MTU_8192;
> +	else
> +		return ((enum opa_mtu)ib_mtu_int_to_enum(mtu));
> +}
> +
>  enum ib_port_state {
>  	IB_PORT_NOP		= 0,
>  	IB_PORT_DOWN		= 1,
> @@ -651,6 +678,7 @@ struct ib_port_attr {
>  	enum ib_port_state	state;
>  	enum ib_mtu		max_mtu;
>  	enum ib_mtu		active_mtu;
> +	u32                     phys_mtu;
>  	int			gid_tbl_len;
>  	unsigned int		ip_gids:1;
>  	/* This is the value from PortInfo CapabilityMask, defined by IBA */
> @@ -3364,6 +3392,55 @@ static inline unsigned int rdma_find_pg_bit(unsigned long addr,
>  	return __fls(pgsz);
>  }
>  
> +/**
> + * rdma_core_cap_opa_port - Return whether the RDMA Port is OPA or not.
> + * @device: Device
> + * @port_num: 1 based Port number
> + *
> + * Return true if port is an Intel OPA port , false if not
> + */
> +static inline bool rdma_core_cap_opa_port(struct ib_device *device,
> +					  u32 port_num)
> +{
> +	return (device->port_data[port_num].immutable.core_cap_flags &
> +		RDMA_CORE_PORT_INTEL_OPA) == RDMA_CORE_PORT_INTEL_OPA;
> +}
> +
> +/**
> + * rdma_mtu_enum_to_int - Return the mtu of the port as an integer value.
> + * @device: Device
> + * @port_num: Port number
> + * @mtu: enum value of MTU
> + *
> + * Return the MTU size supported by the port as an integer value. Will return
> + * -1 if enum value of mtu is not supported.
> + */
> +static inline int rdma_mtu_enum_to_int(struct ib_device *device, u8 port,
> +				       int mtu)
> +{
> +	if (rdma_core_cap_opa_port(device, port))
> +		return opa_mtu_enum_to_int((enum opa_mtu)mtu);
> +	else
> +		return ib_mtu_enum_to_int((enum ib_mtu)mtu);
> +}
> +
> +/**
> + * rdma_mtu_from_attr - Return the mtu of the port from the port attribute.
> + * @device: Device
> + * @port_num: Port number
> + * @attr: port attribute
> + *
> + * Return the MTU size supported by the port as an integer value.
> + */
> +static inline int rdma_mtu_from_attr(struct ib_device *device, u8 port,
> +				     struct ib_port_attr *attr)
> +{
> +	if (rdma_core_cap_opa_port(device, port))
> +		return attr->phys_mtu;
> +	else
> +		return ib_mtu_enum_to_int(attr->max_mtu);
> +}
> +
>  int ib_set_vf_link_state(struct ib_device *device, int vf, u8 port,
>  			 int state);
>  int ib_get_vf_config(struct ib_device *device, int vf, u8 port,
> diff --git a/include/rdma/opa_port_info.h b/include/rdma/opa_port_info.h
> index bdbfe25..0d9e6d7 100644
> --- a/include/rdma/opa_port_info.h
> +++ b/include/rdma/opa_port_info.h
> @@ -1,5 +1,5 @@
>  /*
> - * Copyright (c) 2014-2017 Intel Corporation.  All rights reserved.
> + * Copyright (c) 2014-2020 Intel Corporation.  All rights reserved.
>   *
>   * This software is available to you under a choice of one of two
>   * licenses.  You may choose to be licensed under the terms of the GNU
> @@ -139,14 +139,6 @@
>  #define OPA_CAP_MASK3_IsVLMarkerSupported         (1 << 1)
>  #define OPA_CAP_MASK3_IsVLrSupported              (1 << 0)
>  
> -/**
> - * new MTU values
> - */
> -enum {
> -	OPA_MTU_8192  = 6,
> -	OPA_MTU_10240 = 7,
> -};
> -
>  enum {
>  	OPA_PORT_PHYS_CONF_DISCONNECTED = 0,
>  	OPA_PORT_PHYS_CONF_STANDARD     = 1,
> 

This patch introduces a new clang warning:

drivers/infiniband/hw/hfi1/qp.c:198:9: warning: implicit conversion from enumeration type 'enum opa_mtu' to different enumeration type 'enum ib_mtu' [-Wenum-conversion]
                mtu = OPA_MTU_8192;
                    ~ ^~~~~~~~~~~~
1 warning generated.

The simple solution is obviously to just remove the cast but then I
noticed all of the explicit casts along with the casts in the conversion
functions. What is the point of having these values as enums then
explicitly casting them to others? Doesn't that just remove the type
safety that enums offer? Wouldn't it just be better to have preprocessor
defines? I noticed that OPA_MTU_0 to OPA_MTU_4096 are done that way but
then OPA_MTU_8192 and OPA_MTU_10240 are defined as enumerators... I
spent at least 15 minutes looking into how to untangle all of this and
just decided to sent this email instead. I am happy to just send a patch
shutting up this warning with a cast but I think the better long term
solution is to just consolidate these enums/functions into something
less unweildy.

Cheers,
Nathan