Re: [PATCH v2 1/8] memregion: Support fine grained invalidate by cpu_cache_invalidate_memregion()

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

Jonathan Cameron wrote:
> From: Yicong Yang <yangyicong@hisilicon.com>
> 
> Extend cpu_cache_invalidate_memregion() to support invalidate certain
> range of memory. Control of types of invlidation is left for when

s/invlidation/invalidation/

> usecases turn up. For now everything is Clean and Invalidate.
> 
> Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
> Signed-off-by: Jonathan Cameron <jonathan.cameron@huawei.com>
> ---
>  arch/x86/mm/pat/set_memory.c | 2 +-
>  drivers/cxl/core/region.c    | 6 +++++-
>  drivers/nvdimm/region.c      | 3 ++-
>  drivers/nvdimm/region_devs.c | 3 ++-
>  include/linux/memregion.h    | 8 ++++++--
>  5 files changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
> index 46edc11726b7..8b39aad22458 100644
> --- a/arch/x86/mm/pat/set_memory.c
> +++ b/arch/x86/mm/pat/set_memory.c
> @@ -368,7 +368,7 @@ bool cpu_cache_has_invalidate_memregion(void)
>  }
>  EXPORT_SYMBOL_NS_GPL(cpu_cache_has_invalidate_memregion, "DEVMEM");
>  
> -int cpu_cache_invalidate_memregion(int res_desc)
> +int cpu_cache_invalidate_memregion(int res_desc, phys_addr_t start, size_t len)
>  {
>  	if (WARN_ON_ONCE(!cpu_cache_has_invalidate_memregion()))
>  		return -ENXIO;
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 6e5e1460068d..6e6e8ace0897 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -237,7 +237,11 @@ static int cxl_region_invalidate_memregion(struct cxl_region *cxlr)
>  		return -ENXIO;
>  	}
>  
> -	cpu_cache_invalidate_memregion(IORES_DESC_CXL);
> +	if (!cxlr->params.res)
> +		return -ENXIO;
> +	cpu_cache_invalidate_memregion(IORES_DESC_CXL,
> +				       cxlr->params.res->start,
> +				       resource_size(cxlr->params.res));

So lets abandon the never used @res_desc argument. It was originally
there for documentation and the idea that with HDM-DB CXL invalidation
could be triggered from the device. However, that never came to pass,
and the continued existence of the option is confusing especially if
the range may not be a strict subset of the res_desc.

Alternatively, keep the @res_desc parameter and have the backend lookup
the ranges to flush from the descriptor, but I like that option less.