netdev - [PATCH v6 24/28] cxl: add region flag for precluding a device memory to be used for dax

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Message-ID: <20241202171222.62595-25-alejandro.lucero-palau@amd.com>
Date: Mon, 2 Dec 2024 17:12:18 +0000
From: <alejandro.lucero-palau@....com>
To: <linux-cxl@...r.kernel.org>, <netdev@...r.kernel.org>,
	<dan.j.williams@...el.com>, <martin.habets@...inx.com>,
	<edward.cree@....com>, <davem@...emloft.net>, <kuba@...nel.org>,
	<pabeni@...hat.com>, <edumazet@...gle.com>, <dave.jiang@...el.com>
CC: Alejandro Lucero <alucerop@....com>
Subject: [PATCH v6 24/28] cxl: add region flag for precluding a device memory to be used for dax

From: Alejandro Lucero <alucerop@....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@....com>
---
 drivers/cxl/core/region.c | 10 +++++++++-
 drivers/cxl/cxl.h         |  3 +++
 drivers/cxl/cxlmem.h      |  3 ++-
 include/cxl/cxl.h         |  3 ++-
 4 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 79d5e3a47af3..5cb7991268ce 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -3553,7 +3553,8 @@ __construct_new_region(struct cxl_root_decoder *cxlrd,
  * cxl_region driver.
  */
 struct cxl_region *cxl_create_region(struct cxl_root_decoder *cxlrd,
-				     struct cxl_endpoint_decoder *cxled)
+				     struct cxl_endpoint_decoder *cxled,
+				     bool no_dax)
 {
 	struct cxl_region *cxlr;
 
@@ -3569,6 +3570,10 @@ 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);
@@ -3704,6 +3709,9 @@ 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_DECODER_PMEM:
 		return devm_cxl_add_pmem_region(cxlr);
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 57d6dda3fb4a..cc9e3d859fa6 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -521,6 +521,9 @@ 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 9d874f1cb3bf..712f25f494e0 100644
--- a/drivers/cxl/cxlmem.h
+++ b/drivers/cxl/cxlmem.h
@@ -875,5 +875,6 @@ 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);
+				     struct cxl_endpoint_decoder *cxled,
+				     bool no_dax);
 #endif /* __CXL_MEM_H__ */
diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
index e0ea5b801a2e..14be26358f9c 100644
--- a/include/cxl/cxl.h
+++ b/include/cxl/cxl.h
@@ -61,7 +61,8 @@ struct cxl_endpoint_decoder *cxl_request_dpa(struct cxl_memdev *cxlmd,
 					     resource_size_t max);
 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);
+				     struct cxl_endpoint_decoder *cxled,
+				     bool no_dax);
 
 int cxl_accel_region_detach(struct cxl_endpoint_decoder *cxled);
 #endif
-- 
2.17.1