Re: [PATCH 1/6] RMDA/sw: don't allow drivers using dma_virt_ops on highmem configs

[Jason Gunthorpe <jgg@ziepe.ca>]

On Thu, Nov 05, 2020 at 08:42:00AM +0100, Christoph Hellwig wrote:
> dma_virt_ops requires that all pages have a kernel virtual address.
> Introduce a INFINIBAND_VIRT_DMA Kconfig symbol that depends on !HIGHMEM
> and a large enough dma_addr_t, and make all three driver depend on the
> new symbol.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
>  drivers/infiniband/Kconfig           | 6 ++++++
>  drivers/infiniband/sw/rdmavt/Kconfig | 3 ++-
>  drivers/infiniband/sw/rxe/Kconfig    | 2 +-
>  drivers/infiniband/sw/siw/Kconfig    | 1 +
>  4 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/infiniband/Kconfig b/drivers/infiniband/Kconfig
> index 32a51432ec4f73..81acaf5fb5be67 100644
> +++ b/drivers/infiniband/Kconfig
> @@ -73,6 +73,12 @@ config INFINIBAND_ADDR_TRANS_CONFIGFS
>  	  This allows the user to config the default GID type that the CM
>  	  uses for each device, when initiaing new connections.
>  
> +config INFINIBAND_VIRT_DMA
> +	bool
> +	default y

Oh, I haven't seen this kconfig trick with default before..

> +	depends on !HIGHMEM
> +	depends on !64BIT || ARCH_DMA_ADDR_T_64BIT
> +
>  if INFINIBAND_USER_ACCESS || !INFINIBAND_USER_ACCESS
>  source "drivers/infiniband/hw/mthca/Kconfig"
>  source "drivers/infiniband/hw/qib/Kconfig"
> diff --git a/drivers/infiniband/sw/rdmavt/Kconfig b/drivers/infiniband/sw/rdmavt/Kconfig
> index 9ef5f5ce1ff6b0..c8e268082952b0 100644
> +++ b/drivers/infiniband/sw/rdmavt/Kconfig
> @@ -1,7 +1,8 @@
>  # SPDX-License-Identifier: GPL-2.0-only
>  config INFINIBAND_RDMAVT
>  	tristate "RDMA verbs transport library"
> -	depends on X86_64 && ARCH_DMA_ADDR_T_64BIT
> +	depends on INFINIBAND_VIRT_DMA

Usually I would expect a non-menu item to be used with select not
'depends on' - is the use of default avoiding that?

This looks nice

Jason