netdev - Re: [PATCH v7 24/28] cxl: add region flag for precluding a device memory to be used for dax

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Message-ID: <455f8e81-fa7b-f416-db0d-4ad9ac158865@gmail.com>
Date: Wed, 11 Dec 2024 02:31:01 +0000
From: Edward Cree <ecree.xilinx@...il.com>
To: alejandro.lucero-palau@....com, linux-cxl@...r.kernel.org,
 netdev@...r.kernel.org, dan.j.williams@...el.com, martin.habets@...inx.com,
 edward.cree@....com, davem@...emloft.net, kuba@...nel.org,
 pabeni@...hat.com, edumazet@...gle.com, dave.jiang@...el.com
Cc: Alejandro Lucero <alucerop@....com>
Subject: Re: [PATCH v7 24/28] cxl: add region flag for precluding a device
 memory to be used for dax

On 09/12/2024 18:54, alejandro.lucero-palau@....com wrote:
> From: Alejandro Lucero <alucerop@....com>
> 
> By definition a type2 cxl device will use the host managed memory for
> specific functionality, therefore it should not be available to other
> uses. However, a dax interface could be just good enough in some cases.
> 
> Add a flag to a cxl region for specifically state to not create a dax
> device. Allow a Type2 driver to set that flag at region creation time.
> 
> Signed-off-by: Alejandro Lucero <alucerop@....com>
> Reviewed-by: Zhi Wang <zhiw@...dia.com>
> ---
>  drivers/cxl/core/region.c | 10 +++++++++-
>  drivers/cxl/cxl.h         |  3 +++
>  drivers/cxl/cxlmem.h      |  3 ++-
>  include/cxl/cxl.h         |  3 ++-
>  4 files changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index b014f2fab789..b39086356d74 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -3562,7 +3562,8 @@ __construct_new_region(struct cxl_root_decoder *cxlrd,
>   * cxl_region driver.
>   */
>  struct cxl_region *cxl_create_region(struct cxl_root_decoder *cxlrd,
> -				     struct cxl_endpoint_decoder *cxled)
> +				     struct cxl_endpoint_decoder *cxled,
> +				     bool no_dax)

Won't this break bisectability?  sfc won't build as of this commit
 because it tries to call cxl_create_region with the old signature.
You could do the whole dance of having an interim API during the
 conversion, but seems simpler just to reorder the patches so that
 the no_dax parameter is added first before the caller is introduced.