Re: [PATCH v25 07/11] cxl: Add function for obtaining region range

[Dan Williams <dan.j.williams@intel.com>]

alejandro.lucero-palau@ wrote:
> From: Alejandro Lucero <alucerop@amd.com>
> 
> A CXL region struct contains the physical address to work with.
> 
> Type2 drivers can create a CXL region but have not access to the
> related struct as it is defined as private by the kernel CXL core.
> Add a function for getting the cxl region range to be used for mapping
> such memory range by a Type2 driver.
> 
> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
> Reviewed-by: Zhi Wang <zhiw@nvidia.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> Reviewed-by: Ben Cheatham <benjamin.cheatham@amd.com>
> ---
>  drivers/cxl/core/region.c | 23 +++++++++++++++++++++++
>  include/cxl/cxl.h         |  2 ++
>  2 files changed, 25 insertions(+)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 3edb5703d6de..9c3ba911d865 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -2655,6 +2655,29 @@ static struct cxl_region *devm_cxl_add_region(struct cxl_root_decoder *cxlrd,
>  	return ERR_PTR(rc);
>  }
>  
> +/**
> + * cxl_get_region_range - obtain range linked to a CXL region
> + *
> + * @region: a pointer to struct cxl_region
> + * @range: a pointer to a struct range to be set
> + *
> + * Returns 0 or error.
> + */
> +int cxl_get_region_range(struct cxl_region *region, struct range *range)
> +{
> +	if (WARN_ON_ONCE(!region))
> +		return -ENODEV;
> +
> +	if (!region->params.res)
> +		return -ENOSPC;
> +
> +	range->start = region->params.res->start;
> +	range->end = region->params.res->end;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_get_region_range, "CXL");

Missing locks to keep the range valid until this context can be hooked
up an invalidation path like "unload driver on region destruction", or
other protection against user triggered destruction while the memory is
in use.