Re: [PATCH for-next v3 3/4] RDMA/efa: User/kernel compatibility handshake mechanism

[Jason Gunthorpe <jgg@ziepe.ca>]

On Tue, Jul 21, 2020 at 04:30:48PM +0300, Gal Pressman wrote:
> Introduce a mechanism that performs an handshake between the userspace
> provider and kernel driver which verifies that the user supports all
> required features in order to operate correctly.
> 
> The handshake verifies the needed functionality by comparing the
> reported device caps and the provider caps. If the device reports a
> non-zero capability the appropriate comp mask is required from the
> userspace provider in order to allocate the context.
> 
> Reviewed-by: Shadi Ammouri <sammouri@amazon.com>
> Reviewed-by: Yossi Leybovich <sleybo@amazon.com>
> Signed-off-by: Gal Pressman <galpress@amazon.com>
>  drivers/infiniband/hw/efa/efa_verbs.c | 49 +++++++++++++++++++++++++++
>  include/uapi/rdma/efa-abi.h           | 10 ++++++
>  2 files changed, 59 insertions(+)
> 
> diff --git a/drivers/infiniband/hw/efa/efa_verbs.c b/drivers/infiniband/hw/efa/efa_verbs.c
> index 26102ab333b2..7ca40df81ee5 100644
> +++ b/drivers/infiniband/hw/efa/efa_verbs.c
> @@ -1501,11 +1501,48 @@ static int efa_dealloc_uar(struct efa_dev *dev, u16 uarn)
>  	return efa_com_dealloc_uar(&dev->edev, &params);
>  }
>  
> +#define EFA_CHECK_COMP(_dev, _comp_mask, _attr, _mask)                         \
> +	(!(_dev)->dev_attr._attr || ((_comp_mask) & (_mask)))
> +
> +#define DEFINE_COMP_HANDSHAKE(_dev, _comp_mask, _attr, _mask)                  \
> +	{                                                                      \
> +		.attr = #_attr,                                                \
> +		.check_comp = EFA_CHECK_COMP(_dev, _comp_mask, _attr, _mask)   \
> +	}
> +
> +int efa_user_comp_handshake(const struct ib_ucontext *ibucontext,
> +			    const struct efa_ibv_alloc_ucontext_cmd *cmd)
> +{
> +	struct efa_dev *dev = to_edev(ibucontext->device);
> +	int i;
> +	struct {
> +		char *attr;
> +		bool check_comp;
> +	} user_comp_handshakes[] = {
> +		DEFINE_COMP_HANDSHAKE(dev, cmd->comp_mask, max_tx_batch,
> +				      EFA_ALLOC_UCONTEXT_CMD_COMP_TX_BATCH),
> +		DEFINE_COMP_HANDSHAKE(dev, cmd->comp_mask, min_sq_depth,
> +				      EFA_ALLOC_UCONTEXT_CMD_COMP_MIN_SQ_WR),
> +	};

This seems like a very expensive construct

Why have the array at all? Just list the macros and have them jump to
err

Jason