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

On Wed, 9 Jul 2025 15:31:14 -0700
[off-list ref] wrote:

Jonathan Cameron wrote:

quoted

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/

quoted

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.

I'll do that as a precursor so we can keep the discussion of that
vs the range being added separate.

Jonathan