[PATCH v9 23/27] cxl: add region flag for precluding a device memory to be used for dax

alejandro.lucero-palau
2024-12-30T21:45:34Z

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>
---
drivers/cxl/core/region.c | 11 ++++++++++-
drivers/cxl/cxl.h | 3 +++
drivers/cxl/cxlmem.h | 3 ++-
include/cxl/cxl.h | 3 ++-
4 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index a2b92162edbd..b3a68c1d0652 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -3559,12 +3559,14 @@ __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)
+ struct cxl_endpoint_decoder *cxled,
+ bool no_dax)
{
struct cxl_region *cxlr;

@@ -3580,6 +3582,10 @@ 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");
@@ -3715,6 +3721,9 @@ 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 efdd4627b774..f28873a17443 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 ae024ae8fed8..b681f1382a39 100644
--- a/drivers/cxl/cxlmem.h
+++ b/drivers/cxl/cxlmem.h
@@ -873,5 +873,6 @@ 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 d1264c58f6c0..19f3eef44535 100644
--- a/include/cxl/cxl.h
+++ b/include/cxl/cxl.h
@@ -64,7 +64,8 @@ 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