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

[Davidlohr Bueso <dave@xxxxxxxxxxxx>]

On Tue, 24 Jun 2025, Jonathan Cameron wrote:

> From: Yicong Yang <yangyicong@xxxxxxxxxxxxx>
>
> Extend cpu_cache_invalidate_memregion() to support invalidate certain
> range of memory. Control of types of invlidation is left for when
> usecases turn up. For now everything is Clean and Invalidate.

Yes, this was always the idea for the final interface, but had
kept it simple given x86's big hammer hoping for arm64 solution
to come around.

Acked-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>

> Signed-off-by: Yicong Yang <yangyicong@xxxxxxxxxxxxx>
> Signed-off-by: Jonathan Cameron <jonathan.cameron@xxxxxxxxxx>
> ---
> 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));
> 	return 0;
> }
>
> diff --git a/drivers/nvdimm/region.c b/drivers/nvdimm/region.c
> index 88dc062af5f8..033e40f4dc52 100644
> --- a/drivers/nvdimm/region.c
> +++ b/drivers/nvdimm/region.c
> @@ -110,7 +110,8 @@ static void nd_region_remove(struct device *dev)
> 	 * here is ok.
> 	 */
> 	if (cpu_cache_has_invalidate_memregion())
> -		cpu_cache_invalidate_memregion(IORES_DESC_PERSISTENT_MEMORY);
> +		cpu_cache_invalidate_memregion(IORES_DESC_PERSISTENT_MEMORY,
> +					       0, -1);
> }
>
> static int child_notify(struct device *dev, void *data)
> diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
> index de1ee5ebc851..7e93766065d1 100644
> --- a/drivers/nvdimm/region_devs.c
> +++ b/drivers/nvdimm/region_devs.c
> @@ -90,7 +90,8 @@ static int nd_region_invalidate_memregion(struct nd_region *nd_region)
> 		}
> 	}
>
> -	cpu_cache_invalidate_memregion(IORES_DESC_PERSISTENT_MEMORY);
> +	cpu_cache_invalidate_memregion(IORES_DESC_PERSISTENT_MEMORY,
> +				       0, -1);
> out:
> 	for (i = 0; i < nd_region->ndr_mappings; i++) {
> 		struct nd_mapping *nd_mapping = &nd_region->mapping[i];
> diff --git a/include/linux/memregion.h b/include/linux/memregion.h
> index c01321467789..91d088ee3695 100644
> --- a/include/linux/memregion.h
> +++ b/include/linux/memregion.h
> @@ -28,6 +28,9 @@ static inline void memregion_free(int id)
>  * cpu_cache_invalidate_memregion - drop any CPU cached data for
>  *     memregions described by @res_desc
>  * @res_desc: one of the IORES_DESC_* types
> + * @start: start physical address of the target memory region.
> + * @len: length of the target memory region. -1 for all the regions of
> + *       the target type.
>  *
>  * Perform cache maintenance after a memory event / operation that
>  * changes the contents of physical memory in a cache-incoherent manner.
> @@ -46,7 +49,7 @@ static inline void memregion_free(int id)
>  * the cache maintenance.
>  */
> #ifdef CONFIG_ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION
> -int cpu_cache_invalidate_memregion(int res_desc);
> +int cpu_cache_invalidate_memregion(int res_desc, phys_addr_t start, size_t len);
> bool cpu_cache_has_invalidate_memregion(void);
> #else
> static inline bool cpu_cache_has_invalidate_memregion(void)
> @@ -54,7 +57,8 @@ static inline bool cpu_cache_has_invalidate_memregion(void)
> 	return false;
> }
>
> -static inline int cpu_cache_invalidate_memregion(int res_desc)
> +static inline int cpu_cache_invalidate_memregion(int res_desc,
> +						 phys_addr_t start, size_t len)
> {
> 	WARN_ON_ONCE("CPU cache invalidation required");
> 	return -ENXIO;
> --
> 2.48.1