[PATCH v10 22/26] cxl: add region flag for precluding a device memory to be used for dax

[<alucerop@amd.com>]

From: Alejandro Lucero <alucerop@amd.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@amd.com>
Reviewed-by: Zhi Wang <zhiw@nvidia.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 drivers/cxl/core/region.c | 11 ++++++++++-
 drivers/cxl/cxl.h         |  3 +++
 drivers/cxl/cxlmem.h      |  2 --
 include/cxl/cxl.h         |  3 ++-
 4 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 55a4b230b5e9..742c03e983d5 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -3580,12 +3580,14 @@ __construct_new_region(struct cxl_root_decoder *cxlrd,
  * cxl_create_region - Establish a region given an endpoint decoder
  * @cxlrd: root decoder to allocate HPA
  * @cxled: endpoint decoder with reserved DPA capacity
+ * @no_dax: if true no DAX device should be created
  *
  * Returns a fully formed region in the commit state and attached to the
  * cxl_region driver.
  */
 struct cxl_region *cxl_create_region(struct cxl_root_decoder *cxlrd,
-				     struct cxl_endpoint_decoder *cxled, int ways)
+				     struct cxl_endpoint_decoder *cxled, int ways,
+				     bool no_dax)
 {
 	struct cxl_region *cxlr;
 
@@ -3601,6 +3603,10 @@ struct cxl_region *cxl_create_region(struct cxl_root_decoder *cxlrd,
 		drop_region(cxlr);
 		return ERR_PTR(-ENODEV);
 	}
+
+	if (no_dax)
+		set_bit(CXL_REGION_F_NO_DAX, &cxlr->flags);
+
 	return cxlr;
 }
 EXPORT_SYMBOL_NS_GPL(cxl_create_region, "CXL");
@@ -3736,6 +3742,9 @@ static int cxl_region_probe(struct device *dev)
 	if (rc)
 		return rc;
 
+	if (test_bit(CXL_REGION_F_NO_DAX, &cxlr->flags))
+		return 0;
+
 	switch (cxlr->mode) {
 	case CXL_PARTMODE_PMEM:
 		return devm_cxl_add_pmem_region(cxlr);
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index e1a8e3d786af..4f7aaffa04b1 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -494,6 +494,9 @@ struct cxl_region_params {
  */
 #define CXL_REGION_F_NEEDS_RESET 1
 
+/* Allow Type2 drivers to specify if a dax region should not be created. */
+#define CXL_REGION_F_NO_DAX 2
+
 /**
  * struct cxl_region - CXL region
  * @dev: This region's device
diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
index 2b260cf93d7e..760f7e16a6a4 100644
--- a/drivers/cxl/cxlmem.h
+++ b/drivers/cxl/cxlmem.h
@@ -882,6 +882,4 @@ struct cxl_hdm {
 struct seq_file;
 struct dentry *cxl_debugfs_create_dir(const char *dir);
 void cxl_dpa_debug(struct seq_file *file, struct cxl_dev_state *cxlds);
-struct cxl_region *cxl_create_region(struct cxl_root_decoder *cxlrd,
-				     struct cxl_endpoint_decoder *cxled, int ways);
 #endif /* __CXL_MEM_H__ */
diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
index 4f93af062815..6a0625476f24 100644
--- a/include/cxl/cxl.h
+++ b/include/cxl/cxl.h
@@ -95,7 +95,8 @@ struct cxl_endpoint_decoder *cxl_request_dpa(struct cxl_memdev *cxlmd,
 					     resource_size_t alloc);
 int cxl_dpa_free(struct cxl_endpoint_decoder *cxled);
 struct cxl_region *cxl_create_region(struct cxl_root_decoder *cxlrd,
-				     struct cxl_endpoint_decoder *cxled, int ways);
+				     struct cxl_endpoint_decoder *cxled, int ways,
+				     bool no_dax);
 
 int cxl_accel_region_detach(struct cxl_endpoint_decoder *cxled);
 #endif
-- 
2.17.1