Subject: Re: [PATCH net-next] net/mlx4_core: Fix backward compatibility on VFs

From: Alexey Kardashevskiy <[email-masked]>
Date: Fri, 18 Mar 2016 20:45:19 +1100

On 03/18/2016 03:49 AM, Eli Cohen wrote:
> Commit 85743f1eb345 ("net/mlx4_core: Set UAR page size to 4KB regardless
> of system page size") introduced dependency where old VF drivers without
> this fix fail to load if the PF driver runs with this commit.
>
> To resolve this add a module parameter which disables that functionality
> by default.  If both the PF and VFs are running with a driver with that
> commit the administrator may set the module param to true.
>
> The module parameter is called enable_4k_uar.
>
> Fixes: 85743f1eb345 ('net/mlx4_core: Set UAR page size to 4KB ...')
> Signed-off-by: Eli Cohen <eli-VPRAkNaXOzVWk0Htik3J/[email-masked]>

Thanks!

Tested-by: Alexey Kardashevskiy <[email-masked]>

> ---
>   drivers/net/ethernet/mellanox/mlx4/main.c | 24 ++++++++++++++++++------
>   1 file changed, 18 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx4/main.c b/drivers/net/ethernet/mellanox/mlx4/main.c
> index 503ec23e84cc..358f7230da58 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/main.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/main.c
> @@ -105,6 +105,11 @@ module_param(enable_64b_cqe_eqe, bool, 0444);
>   MODULE_PARM_DESC(enable_64b_cqe_eqe,
>   		 "Enable 64 byte CQEs/EQEs when the FW supports this (default: True)");
>
> +static bool enable_4k_uar;
> +module_param(enable_4k_uar, bool, 0444);
> +MODULE_PARM_DESC(enable_4k_uar,
> +		 "Enable using 4K UAR. Should not be enabled if have VFs which do not support 4K UARs (default: false)");
> +
>   #define PF_CONTEXT_BEHAVIOUR_MASK	(MLX4_FUNC_CAP_64B_EQE_CQE | \
>   					 MLX4_FUNC_CAP_EQE_CQE_STRIDE | \
>   					 MLX4_FUNC_CAP_DMFS_A0_STATIC)
> @@ -423,7 +428,11 @@ static int mlx4_dev_cap(struct mlx4_dev *dev, struct mlx4_dev_cap *dev_cap)
>   		/* Virtual PCI function needs to determine UAR page size from
>   		 * firmware. Only master PCI function can set the uar page size
>   		 */
> -		dev->uar_page_shift = DEFAULT_UAR_PAGE_SHIFT;
> +		if (enable_4k_uar)
> +			dev->uar_page_shift = DEFAULT_UAR_PAGE_SHIFT;
> +		else
> +			dev->uar_page_shift = PAGE_SHIFT;
> +
>   		mlx4_set_num_reserved_uars(dev, dev_cap);
>   	}
>
> @@ -2233,11 +2242,14 @@ static int mlx4_init_hca(struct mlx4_dev *dev)
>
>   		dev->caps.max_fmr_maps = (1 << (32 - ilog2(dev->caps.num_mpts))) - 1;
>
> -		/* Always set UAR page size 4KB, set log_uar_sz accordingly */
> -		init_hca.log_uar_sz = ilog2(dev->caps.num_uars) +
> -				      PAGE_SHIFT -
> -				      DEFAULT_UAR_PAGE_SHIFT;
> -		init_hca.uar_page_sz = DEFAULT_UAR_PAGE_SHIFT - 12;
> +		if (enable_4k_uar) {
> +			init_hca.log_uar_sz = ilog2(dev->caps.num_uars) +
> +						    PAGE_SHIFT - DEFAULT_UAR_PAGE_SHIFT;
> +			init_hca.uar_page_sz = DEFAULT_UAR_PAGE_SHIFT - 12;
> +		} else {
> +			init_hca.log_uar_sz = ilog2(dev->caps.num_uars);
> +			init_hca.uar_page_sz = PAGE_SHIFT - 12;
> +		}
>
>   		init_hca.mw_enabled = 0;
>   		if (dev->caps.flags & MLX4_DEV_CAP_FLAG_MEM_WINDOW ||
>

-- 
Alexey
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