[ndctl PATCH v2 0/4] ndctl: Add security test for cxl devices through nvdimm

[ndctl PATCH v2 0/4] ndctl: Add security test for cxl devices through nvdimm

[Dave Jiang]

This ndctl series add support to test cxl pmem devices through the nvdimm
interface. A new shell script is added for security test due to the
discovery of cxl_test dimms are different than nfit_test based dimms.
Common code are shared between nfit and cxl security testing.

v2:
- Fix commit logs (Vishal)
- Share common code for test (Vishal)
- Add test to cxl suite (Dan)

---

Dave Jiang (4):
      ndctl: add CXL bus detection
      ndctl/libndctl: Add bus_prefix for CXL
      ndctl/libndctl: Allow retrievng of unique_id for CXL mem dev
      ndctl/test: Add CXL test for security


 ndctl/lib/libndctl.c   | 87 ++++++++++++++++++++++++++++++++++++++++++
 ndctl/lib/libndctl.sym |  1 +
 ndctl/lib/private.h    |  1 +
 ndctl/libndctl.h       |  1 +
 test/common            |  7 ++++
 test/cxl-security      | 40 +++++++++++++++++++
 test/cxl-security.sh   |  5 +++
 test/meson.build       |  6 ++-
 test/nfit-security     | 40 +++++++++++++++++++
 test/nfit-security.sh  |  5 +++
 test/security.sh       | 70 ++++++++++++---------------------
 11 files changed, 216 insertions(+), 47 deletions(-)
 create mode 100644 test/cxl-security
 create mode 100755 test/cxl-security.sh
 create mode 100644 test/nfit-security
 create mode 100755 test/nfit-security.sh

--

[ndctl PATCH v2 1/4] ndctl: add CXL bus detection

[Dave Jiang]

Add a CXL bus type, and detect whether a 'dimm' is backed by the CXL
subsystem.

Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

---
v2:
- Improve commit log. (Vishal)
---
 ndctl/lib/libndctl.c   |   53 ++++++++++++++++++++++++++++++++++++++++++++++++
 ndctl/lib/libndctl.sym |    1 +
 ndctl/lib/private.h    |    1 +
 ndctl/libndctl.h       |    1 +
 4 files changed, 56 insertions(+)

diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
index ad54f0626510..10422e24d38b 100644
--- a/ndctl/lib/libndctl.c
+++ b/ndctl/lib/libndctl.c
@@ -12,6 +12,7 @@
 #include <ctype.h>
 #include <fcntl.h>
 #include <dirent.h>
+#include <libgen.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/ioctl.h>
@@ -876,6 +877,48 @@ static enum ndctl_fwa_method fwa_method_to_method(const char *fwa_method)
 	return NDCTL_FWA_METHOD_RESET;
 }
 
+static int is_ndbus_cxl(const char *ctl_base)
+{
+	char *path, *ppath, *subsys;
+	char tmp_path[PATH_MAX];
+	int rc;
+
+	/* get the real path of ctl_base */
+	path = realpath(ctl_base, NULL);
+	if (!path)
+		return -errno;
+
+	/* setup to get the nd bridge device backing the ctl */
+	sprintf(tmp_path, "%s/device", path);
+	free(path);
+
+	path = realpath(tmp_path, NULL);
+	if (!path)
+		return -errno;
+
+	/* get the parent dir of the ndbus, which should be the nvdimm-bridge */
+	ppath = dirname(path);
+
+	/* setup to get the subsystem of the nvdimm-bridge */
+	sprintf(tmp_path, "%s/%s", ppath, "subsystem");
+	free(path);
+
+	path = realpath(tmp_path, NULL);
+	if (!path)
+		return -errno;
+
+	subsys = basename(path);
+
+	/* check if subsystem is cxl */
+	if (!strcmp(subsys, "cxl"))
+		rc = 1;
+	else
+		rc = 0;
+
+	free(path);
+	return rc;
+}
+
 static void *add_bus(void *parent, int id, const char *ctl_base)
 {
 	char buf[SYSFS_ATTR_SIZE];
@@ -919,6 +962,11 @@ static void *add_bus(void *parent, int id, const char *ctl_base)
 	else
 		bus->has_of_node = 1;
 
+	if (is_ndbus_cxl(ctl_base))
+		bus->has_cxl = 1;
+	else
+		bus->has_cxl = 0;
+
 	sprintf(path, "%s/device/nfit/dsm_mask", ctl_base);
 	if (sysfs_read_attr(ctx, path, buf) < 0)
 		bus->nfit_dsm_mask = 0;
@@ -1050,6 +1098,11 @@ NDCTL_EXPORT int ndctl_bus_has_of_node(struct ndctl_bus *bus)
 	return bus->has_of_node;
 }
 
+NDCTL_EXPORT int ndctl_bus_has_cxl(struct ndctl_bus *bus)
+{
+	return bus->has_cxl;
+}
+
 NDCTL_EXPORT int ndctl_bus_is_papr_scm(struct ndctl_bus *bus)
 {
 	char buf[SYSFS_ATTR_SIZE];
diff --git a/ndctl/lib/libndctl.sym b/ndctl/lib/libndctl.sym
index 75c32b9d4967..2892544d1985 100644
--- a/ndctl/lib/libndctl.sym
+++ b/ndctl/lib/libndctl.sym
@@ -464,4 +464,5 @@ LIBNDCTL_27 {
 } LIBNDCTL_26;
 LIBNDCTL_28 {
 	ndctl_dimm_disable_master_passphrase;
+	ndctl_bus_has_cxl;
 } LIBNDCTL_27;
diff --git a/ndctl/lib/private.h b/ndctl/lib/private.h
index e5c56295556d..46bc8908bd90 100644
--- a/ndctl/lib/private.h
+++ b/ndctl/lib/private.h
@@ -163,6 +163,7 @@ struct ndctl_bus {
 	int regions_init;
 	int has_nfit;
 	int has_of_node;
+	int has_cxl;
 	char *bus_path;
 	char *bus_buf;
 	size_t buf_len;
diff --git a/ndctl/libndctl.h b/ndctl/libndctl.h
index c52e82a6f826..91ef0f42f654 100644
--- a/ndctl/libndctl.h
+++ b/ndctl/libndctl.h
@@ -133,6 +133,7 @@ struct ndctl_bus *ndctl_bus_get_next(struct ndctl_bus *bus);
 struct ndctl_ctx *ndctl_bus_get_ctx(struct ndctl_bus *bus);
 int ndctl_bus_has_nfit(struct ndctl_bus *bus);
 int ndctl_bus_has_of_node(struct ndctl_bus *bus);
+int ndctl_bus_has_cxl(struct ndctl_bus *bus);
 int ndctl_bus_is_papr_scm(struct ndctl_bus *bus);
 unsigned int ndctl_bus_get_major(struct ndctl_bus *bus);
 unsigned int ndctl_bus_get_minor(struct ndctl_bus *bus);

[ndctl PATCH v2 2/4] ndctl/libndctl: Add bus_prefix for CXL

[Dave Jiang]

When the 'ndbus' is backed by CXL, setup the bus_prefix for dimm object
appropriately.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>

---
v2:
- improve commit log. (Vishal)
---
 ndctl/lib/libndctl.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
index 10422e24d38b..d2e800bc840a 100644
--- a/ndctl/lib/libndctl.c
+++ b/ndctl/lib/libndctl.c
@@ -2012,6 +2012,12 @@ static void *add_dimm(void *parent, int id, const char *dimm_base)
 			goto out;
 		}
 		rc =  add_papr_dimm(dimm, dimm_base);
+	} else if (ndctl_bus_has_cxl(bus)) {
+		dimm->bus_prefix = strdup("cxl");
+		if (!dimm->bus_prefix) {
+			rc = -ENOMEM;
+			goto out;
+		}
 	}
 
 	if (rc == -ENODEV) {

[ndctl PATCH v2 3/4] ndctl/libndctl: Allow retrievng of unique_id for CXL mem dev

[Dave Jiang]

With bus_prefix, retrieve the unique_id of CXL mem device. This will
allow selecting a specific CXL mem device for the security test code.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>


---
v2:
- Fix commit subject. (Vishal)
---
 ndctl/lib/libndctl.c |   28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
index d2e800bc840a..c569178b9a3a 100644
--- a/ndctl/lib/libndctl.c
+++ b/ndctl/lib/libndctl.c
@@ -1749,6 +1749,33 @@ NDCTL_EXPORT void ndctl_dimm_refresh_flags(struct ndctl_dimm *dimm)
 		parse_papr_flags(dimm, buf);
 }
 
+static int populate_cxl_dimm_attributes(struct ndctl_dimm *dimm,
+					const char *dimm_base)
+{
+	int rc = 0;
+	char buf[SYSFS_ATTR_SIZE];
+	struct ndctl_ctx *ctx = dimm->bus->ctx;
+	char *path = calloc(1, strlen(dimm_base) + 100);
+	const char *bus_prefix = dimm->bus_prefix;
+
+	if (!path)
+		return -ENOMEM;
+
+	sprintf(path, "%s/%s/id", dimm_base, bus_prefix);
+	if (sysfs_read_attr(ctx, path, buf) == 0) {
+		dimm->unique_id = strdup(buf);
+		if (!dimm->unique_id) {
+			rc = -ENOMEM;
+			goto err_read;
+		}
+	}
+
+ err_read:
+
+	free(path);
+	return rc;
+}
+
 static int populate_dimm_attributes(struct ndctl_dimm *dimm,
 				    const char *dimm_base)
 {
@@ -2018,6 +2045,7 @@ static void *add_dimm(void *parent, int id, const char *dimm_base)
 			rc = -ENOMEM;
 			goto out;
 		}
+		rc = populate_cxl_dimm_attributes(dimm, dimm_base);
 	}
 
 	if (rc == -ENODEV) {

[ndctl PATCH v2 4/4] ndctl/test: Add CXL test for security

[Dave Jiang]

Create security-cxl.sh based off of security.sh for nfit security testing.
The test will test a cxl_test based security commands enabling through
nvdimm.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>

---
v2:
- Have test share common code. (Vishal)
- Add cxl test to cxl test suite. (Dan)
---
 test/common           |    7 +++++
 test/cxl-security     |   40 ++++++++++++++++++++++++++++
 test/cxl-security.sh  |    5 ++++
 test/meson.build      |    6 +++-
 test/nfit-security    |   40 ++++++++++++++++++++++++++++
 test/nfit-security.sh |    5 ++++
 test/security.sh      |   70 ++++++++++++++++++-------------------------------
 7 files changed, 126 insertions(+), 47 deletions(-)
 create mode 100644 test/cxl-security
 create mode 100755 test/cxl-security.sh
 create mode 100644 test/nfit-security
 create mode 100755 test/nfit-security.sh

diff --git a/test/common b/test/common
index 44cc352f6009..b2519c17b34c 100644
--- a/test/common
+++ b/test/common
@@ -47,6 +47,7 @@ fi
 #
 NFIT_TEST_BUS0="nfit_test.0"
 NFIT_TEST_BUS1="nfit_test.1"
+CXL_TEST_BUS="cxl_test"
 ACPI_BUS="ACPI.NFIT"
 E820_BUS="e820"
 
@@ -125,6 +126,12 @@ _cleanup()
 	modprobe -r nfit_test
 }
 
+_cxl_cleanup()
+{
+	$NDCTL disable-region -b $CXL_TEST_BUS all
+	modprobe -r cxl_test
+}
+
 # json2var
 # stdin: json
 #
diff --git a/test/cxl-security b/test/cxl-security
new file mode 100644
index 000000000000..9a28ffd82b0b
--- /dev/null
+++ b/test/cxl-security
@@ -0,0 +1,40 @@
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2022, Intel Corp. All rights reserved.
+
+detect()
+{
+	dev="$($NDCTL list -b "$CXL_TEST_BUS" -D | jq -r 'sort_by(.id) | .[0].dev')"
+	[ -n "$dev" ] || err "$LINENO"
+	id="$($NDCTL list -b "$CXL_TEST_BUS" -D | jq -r 'sort_by(.id) | .[0].id')"
+	[ -n "$id" ] || err "$LINENO"
+}
+
+lock_dimm()
+{
+	$NDCTL disable-dimm "$dev"
+	test_dimm_path=""
+
+	nmem_rpath=$(readlink -f "/sys/bus/nd/devices/${dev}")
+	nmem_bus=$(dirname ${nmem_rpath});
+	bus_provider_path="${nmem_bus}/provider"
+	test -e "$bus_provider_path" || err "$LINENO"
+	bus_provider=$(cat ${bus_provider_path})
+
+	[[ "$bus_provider" == "$CXL_TEST_BUS" ]] || err "$LINENO"
+	bus="cxl"
+	nmem_provider_path="/sys/bus/nd/devices/${dev}/${bus}/provider"
+	nmem_provider=$(cat ${nmem_provider_path})
+
+	test_dimm_path=$(readlink -f /sys/bus/$bus/devices/${nmem_provider})
+	test_dimm_path=$(dirname $(dirname ${test_dimm_path}))/security_lock
+
+	test -e "$test_dimm_path"
+
+	# now lock the dimm
+	echo 1 > "${test_dimm_path}"
+	sstate="$(get_security_state)"
+	if [ "$sstate" != "locked" ]; then
+		echo "Incorrect security state: $sstate expected: locked"
+		err "$LINENO"
+	fi
+}
diff --git a/test/cxl-security.sh b/test/cxl-security.sh
new file mode 100755
index 000000000000..d81ad3fe69d9
--- /dev/null
+++ b/test/cxl-security.sh
@@ -0,0 +1,5 @@
+#!/bin/bash -Ex
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2022 Intel Corporation. All rights reserved.
+
+$(dirname $0)/security.sh cxl
diff --git a/test/meson.build b/test/meson.build
index e0aaf5c6eaa9..a956885f6df6 100644
--- a/test/meson.build
+++ b/test/meson.build
@@ -215,9 +215,11 @@ if get_option('destructive').enabled()
 endif
 
 if get_option('keyutils').enabled()
-  security = find_program('security.sh')
+  nfit_security = find_program('nfit-security.sh')
+  cxl_security = find_program('cxl-security.sh')
   tests += [
-    [ 'security.sh', security, 'ndctl' ]
+    [ 'nfit-security.sh', nfit_security, 'ndctl' ],
+    [ 'cxl-security.sh', cxl_security, 'cxl' ],
   ]
 endif
 
diff --git a/test/nfit-security b/test/nfit-security
new file mode 100644
index 000000000000..a05274ab801b
--- /dev/null
+++ b/test/nfit-security
@@ -0,0 +1,40 @@
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2022, Intel Corp. All rights reserved.
+
+detect()
+{
+	dev="$($NDCTL list -b "$NFIT_TEST_BUS0" -D | jq -r .[0].dev)"
+	[ -n "$dev" ] || err "$LINENO"
+	id="$($NDCTL list -b "$NFIT_TEST_BUS0" -D | jq -r .[0].id)"
+	[ -n "$id" ] || err "$LINENO"
+}
+
+lock_dimm()
+{
+	$NDCTL disable-dimm "$dev"
+	# convert nmemX --> test_dimmY
+	# For now this is the only user of such a conversion so we can leave it
+	# inline. Once a subsequent user arrives we can refactor this to a
+	# helper in test/common:
+	#   get_test_dimm_path "nfit_test.0" "nmem3"
+	handle="$($NDCTL list -b "$NFIT_TEST_BUS0"  -d "$dev" -i | jq -r .[].dimms[0].handle)"
+	test_dimm_path=""
+	for test_dimm in /sys/devices/platform/"$NFIT_TEST_BUS0"/nfit_test_dimm/test_dimm*; do
+		td_handle_file="$test_dimm/handle"
+		test -e "$td_handle_file" || continue
+		td_handle="$(cat "$td_handle_file")"
+		if [[ "$td_handle" -eq "$handle" ]]; then
+			test_dimm_path="$test_dimm"
+			break
+		fi
+	done
+	test -d "$test_dimm_path"
+
+	# now lock the dimm
+	echo 1 > "${test_dimm_path}/lock_dimm"
+	sstate="$(get_security_state)"
+	if [ "$sstate" != "locked" ]; then
+		echo "Incorrect security state: $sstate expected: locked"
+		err "$LINENO"
+	fi
+}
diff --git a/test/nfit-security.sh b/test/nfit-security.sh
new file mode 100755
index 000000000000..3df9392438ab
--- /dev/null
+++ b/test/nfit-security.sh
@@ -0,0 +1,5 @@
+#!/bin/bash -Ex
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2022 Intel Corporation. All rights reserved.
+
+$(dirname $0)/security.sh nfit
diff --git a/test/security.sh b/test/security.sh
index 1aa848839ea7..04f630e1946e 100755
--- a/test/security.sh
+++ b/test/security.sh
@@ -17,15 +17,7 @@ trap 'err $LINENO' ERR
 
 setup()
 {
-	$NDCTL disable-region -b "$NFIT_TEST_BUS0" all
-}
-
-detect()
-{
-	dev="$($NDCTL list -b "$NFIT_TEST_BUS0" -D | jq -r .[0].dev)"
-	[ -n "$dev" ] || err "$LINENO"
-	id="$($NDCTL list -b "$NFIT_TEST_BUS0" -D | jq -r .[0].id)"
-	[ -n "$id" ] || err "$LINENO"
+	$NDCTL disable-region -b "$TEST_BUS" all
 }
 
 setup_keys()
@@ -78,44 +70,14 @@ post_cleanup()
 	fi
 }
 
-lock_dimm()
-{
-	$NDCTL disable-dimm "$dev"
-	# convert nmemX --> test_dimmY
-	# For now this is the only user of such a conversion so we can leave it
-	# inline. Once a subsequent user arrives we can refactor this to a
-	# helper in test/common:
-	#   get_test_dimm_path "nfit_test.0" "nmem3"
-	handle="$($NDCTL list -b "$NFIT_TEST_BUS0"  -d "$dev" -i | jq -r .[].dimms[0].handle)"
-	test_dimm_path=""
-	for test_dimm in /sys/devices/platform/"$NFIT_TEST_BUS0"/nfit_test_dimm/test_dimm*; do
-		td_handle_file="$test_dimm/handle"
-		test -e "$td_handle_file" || continue
-		td_handle="$(cat "$td_handle_file")"
-		if [[ "$td_handle" -eq "$handle" ]]; then
-			test_dimm_path="$test_dimm"
-			break
-		fi
-	done
-	test -d "$test_dimm_path"
-
-	# now lock the dimm
-	echo 1 > "${test_dimm_path}/lock_dimm"
-	sstate="$(get_security_state)"
-	if [ "$sstate" != "locked" ]; then
-		echo "Incorrect security state: $sstate expected: locked"
-		err "$LINENO"
-	fi
-}
-
 get_frozen_state()
 {
-	$NDCTL list -i -b "$NFIT_TEST_BUS0" -d "$dev" | jq -r .[].dimms[0].security_frozen
+	$NDCTL list -i -b "$TEST_BUS" -d "$dev" | jq -r .[].dimms[0].security_frozen
 }
 
 get_security_state()
 {
-	$NDCTL list -i -b "$NFIT_TEST_BUS0" -d "$dev" | jq -r .[].dimms[0].security
+	$NDCTL list -i -b "$TEST_BUS" -d "$dev" | jq -r .[].dimms[0].security
 }
 
 setup_passphrase()
@@ -192,7 +154,7 @@ test_4_security_unlock()
 		echo "Incorrect security state: $sstate expected: unlocked"
 		err "$LINENO"
 	fi
-	$NDCTL disable-region -b "$NFIT_TEST_BUS0" all
+	$NDCTL disable-region -b "$TEST_BUS" all
 	remove_passphrase
 }
 
@@ -243,13 +205,26 @@ test_6_load_keys()
 	fi
 }
 
-check_min_kver "5.0" || do_skip "may lack security handling"
+if [ "$1" = "nfit" ]; then
+	. $(dirname $0)/nfit-security
+	TEST_BUS="$NFIT_TEST_BUS0"
+	check_min_kver "5.0" || do_skip "may lack security handling"
+	KMOD_TEST="nfit_test"
+elif [ "$1" = "cxl" ]; then
+	. $(dirname $0)/cxl-security
+	TEST_BUS="$CXL_TEST_BUS"
+	check_min_kver "6.2" || do_skip "may lack security handling"
+	KMOD_TEST="cxl_test"
+else
+	do_skip "Missing input parameters"
+fi
+
 uid="$(keyctl show | grep -Eo "_uid.[0-9]+" | head -1 | cut -d. -f2-)"
 if [ "$uid" -ne 0 ]; then
 	do_skip "run as root or with a sudo login shell for test to work"
 fi
 
-modprobe nfit_test
+modprobe "$KMOD_TEST"
 setup
 check_prereq "keyctl"
 rc=1
@@ -278,5 +253,10 @@ test_6_load_keys
 
 test_cleanup
 post_cleanup
-_cleanup
+if [ "$1" = "nfit" ]; then
+	_cleanup
+elif [ "$1" = "cxl" ]; then
+	_cxl_cleanup
+fi
+
 exit 0

RE: [ndctl PATCH v2 1/4] ndctl: add CXL bus detection

[Dan Williams]

Dave Jiang wrote:
> Add a CXL bus type, and detect whether a 'dimm' is backed by the CXL
> subsystem.
> 
> Reviewed-by: Alison Schofield <alison.schofield@intel.com>
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> 
> ---
> v2:
> - Improve commit log. (Vishal)
> ---
>  ndctl/lib/libndctl.c   |   53 ++++++++++++++++++++++++++++++++++++++++++++++++
>  ndctl/lib/libndctl.sym |    1 +
>  ndctl/lib/private.h    |    1 +
>  ndctl/libndctl.h       |    1 +
>  4 files changed, 56 insertions(+)
> 
> diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
> index ad54f0626510..10422e24d38b 100644
> --- a/ndctl/lib/libndctl.c
> +++ b/ndctl/lib/libndctl.c
> @@ -12,6 +12,7 @@
>  #include <ctype.h>
>  #include <fcntl.h>
>  #include <dirent.h>
> +#include <libgen.h>

This new include had me looking for why below...

>  #include <sys/stat.h>
>  #include <sys/types.h>
>  #include <sys/ioctl.h>
> @@ -876,6 +877,48 @@ static enum ndctl_fwa_method fwa_method_to_method(const char *fwa_method)
>  	return NDCTL_FWA_METHOD_RESET;
>  }
>  
> +static int is_ndbus_cxl(const char *ctl_base)
> +{
> +	char *path, *ppath, *subsys;
> +	char tmp_path[PATH_MAX];
> +	int rc;
> +
> +	/* get the real path of ctl_base */
> +	path = realpath(ctl_base, NULL);
> +	if (!path)
> +		return -errno;
> +
> +	/* setup to get the nd bridge device backing the ctl */
> +	sprintf(tmp_path, "%s/device", path);
> +	free(path);
> +
> +	path = realpath(tmp_path, NULL);
> +	if (!path)
> +		return -errno;
> +
> +	/* get the parent dir of the ndbus, which should be the nvdimm-bridge */
> +	ppath = dirname(path);
> +
> +	/* setup to get the subsystem of the nvdimm-bridge */
> +	sprintf(tmp_path, "%s/%s", ppath, "subsystem");
> +	free(path);
> +
> +	path = realpath(tmp_path, NULL);
> +	if (!path)
> +		return -errno;
> +
> +	subsys = basename(path);
> +
> +	/* check if subsystem is cxl */
> +	if (!strcmp(subsys, "cxl"))
> +		rc = 1;
> +	else
> +		rc = 0;
> +
> +	free(path);
> +	return rc;
> +}
> +
>  static void *add_bus(void *parent, int id, const char *ctl_base)
>  {
>  	char buf[SYSFS_ATTR_SIZE];
> @@ -919,6 +962,11 @@ static void *add_bus(void *parent, int id, const char *ctl_base)
>  	else
>  		bus->has_of_node = 1;
>  
> +	if (is_ndbus_cxl(ctl_base))
> +		bus->has_cxl = 1;
> +	else
> +		bus->has_cxl = 0;
> +

I think you can drop is_ndbus_cxl() and just do this:

@@ -981,6 +976,11 @@ static void *add_bus(void *parent, int id, const char *ctl_base)
        if (!bus->provider)
                goto err_read;
 
+       if (strcasestr("cxl", provider))
+               bus->has_cxl = 1;
+       else
+               bus->has_cxl = 0;
+
        sprintf(path, "%s/device/wait_probe", ctl_base);
        bus->wait_probe_path = strdup(path);
        if (!bus->wait_probe_path)

Re: [ndctl PATCH v2 1/4] ndctl: add CXL bus detection

[Jeff Moyer]

Dan Williams <dan.j.williams@intel.com> writes:

> Dave Jiang wrote:
>> Add a CXL bus type, and detect whether a 'dimm' is backed by the CXL
>> subsystem.
>> 
>> Reviewed-by: Alison Schofield <alison.schofield@intel.com>
>> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
>> 
>> ---
>> v2:
>> - Improve commit log. (Vishal)
>> ---
>>  ndctl/lib/libndctl.c   |   53 ++++++++++++++++++++++++++++++++++++++++++++++++
>>  ndctl/lib/libndctl.sym |    1 +
>>  ndctl/lib/private.h    |    1 +
>>  ndctl/libndctl.h       |    1 +
>>  4 files changed, 56 insertions(+)
>> 
>> diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
>> index ad54f0626510..10422e24d38b 100644
>> --- a/ndctl/lib/libndctl.c
>> +++ b/ndctl/lib/libndctl.c
>> @@ -12,6 +12,7 @@
>>  #include <ctype.h>
>>  #include <fcntl.h>
>>  #include <dirent.h>
>> +#include <libgen.h>
>
> This new include had me looking for why below...

man 3 basename

>>  #include <sys/stat.h>
>>  #include <sys/types.h>
>>  #include <sys/ioctl.h>
>> @@ -876,6 +877,48 @@ static enum ndctl_fwa_method fwa_method_to_method(const char *fwa_method)
>>  	return NDCTL_FWA_METHOD_RESET;
>>  }
>>  
>> +static int is_ndbus_cxl(const char *ctl_base)
>> +{
>> +	char *path, *ppath, *subsys;
>> +	char tmp_path[PATH_MAX];
>> +	int rc;
>> +
>> +	/* get the real path of ctl_base */
>> +	path = realpath(ctl_base, NULL);
>> +	if (!path)
>> +		return -errno;
>> +
>> +	/* setup to get the nd bridge device backing the ctl */
>> +	sprintf(tmp_path, "%s/device", path);
>> +	free(path);
>> +
>> +	path = realpath(tmp_path, NULL);
>> +	if (!path)
>> +		return -errno;
>> +
>> +	/* get the parent dir of the ndbus, which should be the nvdimm-bridge */
>> +	ppath = dirname(path);
>> +
>> +	/* setup to get the subsystem of the nvdimm-bridge */
>> +	sprintf(tmp_path, "%s/%s", ppath, "subsystem");
>> +	free(path);
>> +
>> +	path = realpath(tmp_path, NULL);
>> +	if (!path)
>> +		return -errno;
>> +
>> +	subsys = basename(path);
>> +
>> +	/* check if subsystem is cxl */
>> +	if (!strcmp(subsys, "cxl"))
>> +		rc = 1;
>> +	else
>> +		rc = 0;
>> +
>> +	free(path);
>> +	return rc;
>> +}
>> +
>>  static void *add_bus(void *parent, int id, const char *ctl_base)
>>  {
>>  	char buf[SYSFS_ATTR_SIZE];
>> @@ -919,6 +962,11 @@ static void *add_bus(void *parent, int id, const char *ctl_base)
>>  	else
>>  		bus->has_of_node = 1;
>>  
>> +	if (is_ndbus_cxl(ctl_base))
>> +		bus->has_cxl = 1;
>> +	else
>> +		bus->has_cxl = 0;
>> +
>
> I think you can drop is_ndbus_cxl() and just do this:
>
> @@ -981,6 +976,11 @@ static void *add_bus(void *parent, int id, const char *ctl_base)
>         if (!bus->provider)
>                 goto err_read;
>  
> +       if (strcasestr("cxl", provider))
> +               bus->has_cxl = 1;
> +       else
> +               bus->has_cxl = 0;
> +

Can you explain why this is preferred?

Cheers,
Jeff

Re: [ndctl PATCH v2 1/4] ndctl: add CXL bus detection

[Dan Williams]

Jeff Moyer wrote:
> Dan Williams <dan.j.williams@intel.com> writes:
> 
> > Dave Jiang wrote:
> >> Add a CXL bus type, and detect whether a 'dimm' is backed by the CXL
> >> subsystem.
> >> 
> >> Reviewed-by: Alison Schofield <alison.schofield@intel.com>
> >> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> >> 
> >> ---
> >> v2:
> >> - Improve commit log. (Vishal)
> >> ---
> >>  ndctl/lib/libndctl.c   |   53 ++++++++++++++++++++++++++++++++++++++++++++++++
> >>  ndctl/lib/libndctl.sym |    1 +
> >>  ndctl/lib/private.h    |    1 +
> >>  ndctl/libndctl.h       |    1 +
> >>  4 files changed, 56 insertions(+)
> >> 
> >> diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
> >> index ad54f0626510..10422e24d38b 100644
> >> --- a/ndctl/lib/libndctl.c
> >> +++ b/ndctl/lib/libndctl.c
> >> @@ -12,6 +12,7 @@
> >>  #include <ctype.h>
> >>  #include <fcntl.h>
> >>  #include <dirent.h>
> >> +#include <libgen.h>
> >
> > This new include had me looking for why below...
> 
> man 3 basename
> 
> >>  #include <sys/stat.h>
> >>  #include <sys/types.h>
> >>  #include <sys/ioctl.h>
> >> @@ -876,6 +877,48 @@ static enum ndctl_fwa_method fwa_method_to_method(const char *fwa_method)
> >>  	return NDCTL_FWA_METHOD_RESET;
> >>  }
> >>  
> >> +static int is_ndbus_cxl(const char *ctl_base)
> >> +{
> >> +	char *path, *ppath, *subsys;
> >> +	char tmp_path[PATH_MAX];
> >> +	int rc;
> >> +
> >> +	/* get the real path of ctl_base */
> >> +	path = realpath(ctl_base, NULL);
> >> +	if (!path)
> >> +		return -errno;
> >> +
> >> +	/* setup to get the nd bridge device backing the ctl */
> >> +	sprintf(tmp_path, "%s/device", path);
> >> +	free(path);
> >> +
> >> +	path = realpath(tmp_path, NULL);
> >> +	if (!path)
> >> +		return -errno;
> >> +
> >> +	/* get the parent dir of the ndbus, which should be the nvdimm-bridge */
> >> +	ppath = dirname(path);
> >> +
> >> +	/* setup to get the subsystem of the nvdimm-bridge */
> >> +	sprintf(tmp_path, "%s/%s", ppath, "subsystem");
> >> +	free(path);
> >> +
> >> +	path = realpath(tmp_path, NULL);
> >> +	if (!path)
> >> +		return -errno;
> >> +
> >> +	subsys = basename(path);
> >> +
> >> +	/* check if subsystem is cxl */
> >> +	if (!strcmp(subsys, "cxl"))
> >> +		rc = 1;
> >> +	else
> >> +		rc = 0;
> >> +
> >> +	free(path);
> >> +	return rc;
> >> +}
> >> +
> >>  static void *add_bus(void *parent, int id, const char *ctl_base)
> >>  {
> >>  	char buf[SYSFS_ATTR_SIZE];
> >> @@ -919,6 +962,11 @@ static void *add_bus(void *parent, int id, const char *ctl_base)
> >>  	else
> >>  		bus->has_of_node = 1;
> >>  
> >> +	if (is_ndbus_cxl(ctl_base))
> >> +		bus->has_cxl = 1;
> >> +	else
> >> +		bus->has_cxl = 0;
> >> +
> >
> > I think you can drop is_ndbus_cxl() and just do this:
> >
> > @@ -981,6 +976,11 @@ static void *add_bus(void *parent, int id, const char *ctl_base)
> >         if (!bus->provider)
> >                 goto err_read;
> >  
> > +       if (strcasestr("cxl", provider))
> > +               bus->has_cxl = 1;
> > +       else
> > +               bus->has_cxl = 0;
> > +
> 
> Can you explain why this is preferred?

Just less code to achieve a similar result. I do like the precision of
looking at the subsytem of bus device parent, just not the multiple
calls to realpath() with dirname() and basename() thrown in which struck
me as unnecessary. How about this:

diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
index c569178b9a3a..76bd7167bc70 100644
--- a/ndctl/lib/libndctl.c
+++ b/ndctl/lib/libndctl.c
@@ -877,40 +877,16 @@ static enum ndctl_fwa_method fwa_method_to_method(const char *fwa_method)
        return NDCTL_FWA_METHOD_RESET;
 }
 
-static int is_ndbus_cxl(const char *ctl_base)
+static int is_subsys_cxl(const char *subsys)
 {
-       char *path, *ppath, *subsys;
-       char tmp_path[PATH_MAX];
+       char *path;
        int rc;
 
-       /* get the real path of ctl_base */
-       path = realpath(ctl_base, NULL);
+       path = realpath(subsys, NULL);
        if (!path)
                return -errno;
 
-       /* setup to get the nd bridge device backing the ctl */
-       sprintf(tmp_path, "%s/device", path);
-       free(path);
-
-       path = realpath(tmp_path, NULL);
-       if (!path)
-               return -errno;
-
-       /* get the parent dir of the ndbus, which should be the nvdimm-bridge */
-       ppath = dirname(path);
-
-       /* setup to get the subsystem of the nvdimm-bridge */
-       sprintf(tmp_path, "%s/%s", ppath, "subsystem");
-       free(path);
-
-       path = realpath(tmp_path, NULL);
-       if (!path)
-               return -errno;
-
-       subsys = basename(path);
-
-       /* check if subsystem is cxl */
-       if (!strcmp(subsys, "cxl"))
+       if (!strcmp(subsys, "/sys/bus/cxl"))
                rc = 1;
        else
                rc = 0;
@@ -962,7 +938,8 @@ static void *add_bus(void *parent, int id, const char *ctl_base)
        else
                bus->has_of_node = 1;
 
-       if (is_ndbus_cxl(ctl_base))
+       sprintf(path, "%s/device/../subsys", ctl_base);
+       if (is_subsys_cxl(path))
                bus->has_cxl = 1;
        else
                bus->has_cxl = 0;

[ndctl PATCH v3 1/4] ndctl: add CXL bus detection

[Dave Jiang]

Add a CXL bus type, and detect whether a 'dimm' is backed by the CXL
subsystem.

Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

---
v3:
- Simplify detecting cxl subsystem. (Dan)
v2:
- Improve commit log. (Vishal)
---
 ndctl/lib/libndctl.c   |   30 ++++++++++++++++++++++++++++++
 ndctl/lib/libndctl.sym |    1 +
 ndctl/lib/private.h    |    1 +
 ndctl/libndctl.h       |    1 +
 4 files changed, 33 insertions(+)

diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
index ad54f0626510..9cd5340b5702 100644
--- a/ndctl/lib/libndctl.c
+++ b/ndctl/lib/libndctl.c
@@ -12,6 +12,7 @@
 #include <ctype.h>
 #include <fcntl.h>
 #include <dirent.h>
+#include <libgen.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/ioctl.h>
@@ -876,6 +877,24 @@ static enum ndctl_fwa_method fwa_method_to_method(const char *fwa_method)
 	return NDCTL_FWA_METHOD_RESET;
 }
 
+static int is_subsys_cxl(const char *subsys)
+{
+	char *path;
+	int rc;
+
+	path = realpath(subsys, NULL);
+	if (!path)
+		return -errno;
+
+	if (!strcmp(subsys, "/sys/bus/cxl"))
+		rc = 1;
+	else
+		rc = 0;
+
+	free(path);
+	return rc;
+}
+
 static void *add_bus(void *parent, int id, const char *ctl_base)
 {
 	char buf[SYSFS_ATTR_SIZE];
@@ -919,6 +938,12 @@ static void *add_bus(void *parent, int id, const char *ctl_base)
 	else
 		bus->has_of_node = 1;
 
+	sprintf(path, "%s/device/../subsys", ctl_base);
+	if (is_subsys_cxl(path))
+		bus->has_cxl = 1;
+	else
+		bus->has_cxl = 0;
+
 	sprintf(path, "%s/device/nfit/dsm_mask", ctl_base);
 	if (sysfs_read_attr(ctx, path, buf) < 0)
 		bus->nfit_dsm_mask = 0;
@@ -1050,6 +1075,11 @@ NDCTL_EXPORT int ndctl_bus_has_of_node(struct ndctl_bus *bus)
 	return bus->has_of_node;
 }
 
+NDCTL_EXPORT int ndctl_bus_has_cxl(struct ndctl_bus *bus)
+{
+	return bus->has_cxl;
+}
+
 NDCTL_EXPORT int ndctl_bus_is_papr_scm(struct ndctl_bus *bus)
 {
 	char buf[SYSFS_ATTR_SIZE];
diff --git a/ndctl/lib/libndctl.sym b/ndctl/lib/libndctl.sym
index 75c32b9d4967..2892544d1985 100644
--- a/ndctl/lib/libndctl.sym
+++ b/ndctl/lib/libndctl.sym
@@ -464,4 +464,5 @@ LIBNDCTL_27 {
 } LIBNDCTL_26;
 LIBNDCTL_28 {
 	ndctl_dimm_disable_master_passphrase;
+	ndctl_bus_has_cxl;
 } LIBNDCTL_27;
diff --git a/ndctl/lib/private.h b/ndctl/lib/private.h
index e5c56295556d..46bc8908bd90 100644
--- a/ndctl/lib/private.h
+++ b/ndctl/lib/private.h
@@ -163,6 +163,7 @@ struct ndctl_bus {
 	int regions_init;
 	int has_nfit;
 	int has_of_node;
+	int has_cxl;
 	char *bus_path;
 	char *bus_buf;
 	size_t buf_len;
diff --git a/ndctl/libndctl.h b/ndctl/libndctl.h
index c52e82a6f826..91ef0f42f654 100644
--- a/ndctl/libndctl.h
+++ b/ndctl/libndctl.h
@@ -133,6 +133,7 @@ struct ndctl_bus *ndctl_bus_get_next(struct ndctl_bus *bus);
 struct ndctl_ctx *ndctl_bus_get_ctx(struct ndctl_bus *bus);
 int ndctl_bus_has_nfit(struct ndctl_bus *bus);
 int ndctl_bus_has_of_node(struct ndctl_bus *bus);
+int ndctl_bus_has_cxl(struct ndctl_bus *bus);
 int ndctl_bus_is_papr_scm(struct ndctl_bus *bus);
 unsigned int ndctl_bus_get_major(struct ndctl_bus *bus);
 unsigned int ndctl_bus_get_minor(struct ndctl_bus *bus);

Re: [ndctl PATCH v3 1/4] ndctl: add CXL bus detection

[Dave Jiang]

On 12/16/2022 10:21 AM, Dave Jiang wrote:
> Add a CXL bus type, and detect whether a 'dimm' is backed by the CXL
> subsystem.
> 
> Reviewed-by: Alison Schofield <alison.schofield@intel.com>
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> 
> ---
> v3:
> - Simplify detecting cxl subsystem. (Dan)
> v2:
> - Improve commit log. (Vishal)
> ---
>   ndctl/lib/libndctl.c   |   30 ++++++++++++++++++++++++++++++
>   ndctl/lib/libndctl.sym |    1 +
>   ndctl/lib/private.h    |    1 +
>   ndctl/libndctl.h       |    1 +
>   4 files changed, 33 insertions(+)
> 
> diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
> index ad54f0626510..9cd5340b5702 100644
> --- a/ndctl/lib/libndctl.c
> +++ b/ndctl/lib/libndctl.c
> @@ -12,6 +12,7 @@
>   #include <ctype.h>
>   #include <fcntl.h>
>   #include <dirent.h>
> +#include <libgen.h>

Of course I missed removing this change.

>   #include <sys/stat.h>
>   #include <sys/types.h>
>   #include <sys/ioctl.h>
> @@ -876,6 +877,24 @@ static enum ndctl_fwa_method fwa_method_to_method(const char *fwa_method)
>   	return NDCTL_FWA_METHOD_RESET;
>   }
>   
> +static int is_subsys_cxl(const char *subsys)
> +{
> +	char *path;
> +	int rc;
> +
> +	path = realpath(subsys, NULL);
> +	if (!path)
> +		return -errno;
> +
> +	if (!strcmp(subsys, "/sys/bus/cxl"))
> +		rc = 1;
> +	else
> +		rc = 0;
> +
> +	free(path);
> +	return rc;
> +}
> +
>   static void *add_bus(void *parent, int id, const char *ctl_base)
>   {
>   	char buf[SYSFS_ATTR_SIZE];
> @@ -919,6 +938,12 @@ static void *add_bus(void *parent, int id, const char *ctl_base)
>   	else
>   		bus->has_of_node = 1;
>   
> +	sprintf(path, "%s/device/../subsys", ctl_base);
> +	if (is_subsys_cxl(path))
> +		bus->has_cxl = 1;
> +	else
> +		bus->has_cxl = 0;
> +
>   	sprintf(path, "%s/device/nfit/dsm_mask", ctl_base);
>   	if (sysfs_read_attr(ctx, path, buf) < 0)
>   		bus->nfit_dsm_mask = 0;
> @@ -1050,6 +1075,11 @@ NDCTL_EXPORT int ndctl_bus_has_of_node(struct ndctl_bus *bus)
>   	return bus->has_of_node;
>   }
>   
> +NDCTL_EXPORT int ndctl_bus_has_cxl(struct ndctl_bus *bus)
> +{
> +	return bus->has_cxl;
> +}
> +
>   NDCTL_EXPORT int ndctl_bus_is_papr_scm(struct ndctl_bus *bus)
>   {
>   	char buf[SYSFS_ATTR_SIZE];
> diff --git a/ndctl/lib/libndctl.sym b/ndctl/lib/libndctl.sym
> index 75c32b9d4967..2892544d1985 100644
> --- a/ndctl/lib/libndctl.sym
> +++ b/ndctl/lib/libndctl.sym
> @@ -464,4 +464,5 @@ LIBNDCTL_27 {
>   } LIBNDCTL_26;
>   LIBNDCTL_28 {
>   	ndctl_dimm_disable_master_passphrase;
> +	ndctl_bus_has_cxl;
>   } LIBNDCTL_27;
> diff --git a/ndctl/lib/private.h b/ndctl/lib/private.h
> index e5c56295556d..46bc8908bd90 100644
> --- a/ndctl/lib/private.h
> +++ b/ndctl/lib/private.h
> @@ -163,6 +163,7 @@ struct ndctl_bus {
>   	int regions_init;
>   	int has_nfit;
>   	int has_of_node;
> +	int has_cxl;
>   	char *bus_path;
>   	char *bus_buf;
>   	size_t buf_len;
> diff --git a/ndctl/libndctl.h b/ndctl/libndctl.h
> index c52e82a6f826..91ef0f42f654 100644
> --- a/ndctl/libndctl.h
> +++ b/ndctl/libndctl.h
> @@ -133,6 +133,7 @@ struct ndctl_bus *ndctl_bus_get_next(struct ndctl_bus *bus);
>   struct ndctl_ctx *ndctl_bus_get_ctx(struct ndctl_bus *bus);
>   int ndctl_bus_has_nfit(struct ndctl_bus *bus);
>   int ndctl_bus_has_of_node(struct ndctl_bus *bus);
> +int ndctl_bus_has_cxl(struct ndctl_bus *bus);
>   int ndctl_bus_is_papr_scm(struct ndctl_bus *bus);
>   unsigned int ndctl_bus_get_major(struct ndctl_bus *bus);
>   unsigned int ndctl_bus_get_minor(struct ndctl_bus *bus);
> 
> 

Re: [ndctl PATCH v3 1/4] ndctl: add CXL bus detection

[Dan Williams]

Dave Jiang wrote:
> 
> 
> On 12/16/2022 10:21 AM, Dave Jiang wrote:
> > Add a CXL bus type, and detect whether a 'dimm' is backed by the CXL
> > subsystem.
> > 
> > Reviewed-by: Alison Schofield <alison.schofield@intel.com>
> > Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> > 
> > ---
> > v3:
> > - Simplify detecting cxl subsystem. (Dan)
> > v2:
> > - Improve commit log. (Vishal)
> > ---
> >   ndctl/lib/libndctl.c   |   30 ++++++++++++++++++++++++++++++
> >   ndctl/lib/libndctl.sym |    1 +
> >   ndctl/lib/private.h    |    1 +
> >   ndctl/libndctl.h       |    1 +
> >   4 files changed, 33 insertions(+)
> > 
> > diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
> > index ad54f0626510..9cd5340b5702 100644
> > --- a/ndctl/lib/libndctl.c
> > +++ b/ndctl/lib/libndctl.c
> > @@ -12,6 +12,7 @@
> >   #include <ctype.h>
> >   #include <fcntl.h>
> >   #include <dirent.h>
> > +#include <libgen.h>
> 
> Of course I missed removing this change.

With this fixed up feel free to add:

Reviewed-by: Dan Williams <dan.j.williams@intel.com>

...for the series.

[ndctl PATCH v4 1/4] ndctl: add CXL bus detection

[Dave Jiang]

Add a CXL bus type, and detect whether a 'dimm' is backed by the CXL
subsystem.

Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

---
v4:
- Remove libgen.h include
v3:
- Simplify detecting cxl subsystem. (Dan)
v2:
- Improve commit log. (Vishal)
---
 ndctl/lib/libndctl.c   |   29 +++++++++++++++++++++++++++++
 ndctl/lib/libndctl.sym |    1 +
 ndctl/lib/private.h    |    1 +
 ndctl/libndctl.h       |    1 +
 4 files changed, 32 insertions(+)

diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
index ad54f0626510..2b06dc8be81a 100644
--- a/ndctl/lib/libndctl.c
+++ b/ndctl/lib/libndctl.c
@@ -876,6 +876,24 @@ static enum ndctl_fwa_method fwa_method_to_method(const char *fwa_method)
 	return NDCTL_FWA_METHOD_RESET;
 }
 
+static int is_subsys_cxl(const char *subsys)
+{
+	char *path;
+	int rc;
+
+	path = realpath(subsys, NULL);
+	if (!path)
+		return -errno;
+
+	if (!strcmp(subsys, "/sys/bus/cxl"))
+		rc = 1;
+	else
+		rc = 0;
+
+	free(path);
+	return rc;
+}
+
 static void *add_bus(void *parent, int id, const char *ctl_base)
 {
 	char buf[SYSFS_ATTR_SIZE];
@@ -919,6 +937,12 @@ static void *add_bus(void *parent, int id, const char *ctl_base)
 	else
 		bus->has_of_node = 1;
 
+	sprintf(path, "%s/device/../subsys", ctl_base);
+	if (is_subsys_cxl(path))
+		bus->has_cxl = 1;
+	else
+		bus->has_cxl = 0;
+
 	sprintf(path, "%s/device/nfit/dsm_mask", ctl_base);
 	if (sysfs_read_attr(ctx, path, buf) < 0)
 		bus->nfit_dsm_mask = 0;
@@ -1050,6 +1074,11 @@ NDCTL_EXPORT int ndctl_bus_has_of_node(struct ndctl_bus *bus)
 	return bus->has_of_node;
 }
 
+NDCTL_EXPORT int ndctl_bus_has_cxl(struct ndctl_bus *bus)
+{
+	return bus->has_cxl;
+}
+
 NDCTL_EXPORT int ndctl_bus_is_papr_scm(struct ndctl_bus *bus)
 {
 	char buf[SYSFS_ATTR_SIZE];
diff --git a/ndctl/lib/libndctl.sym b/ndctl/lib/libndctl.sym
index 75c32b9d4967..2892544d1985 100644
--- a/ndctl/lib/libndctl.sym
+++ b/ndctl/lib/libndctl.sym
@@ -464,4 +464,5 @@ LIBNDCTL_27 {
 } LIBNDCTL_26;
 LIBNDCTL_28 {
 	ndctl_dimm_disable_master_passphrase;
+	ndctl_bus_has_cxl;
 } LIBNDCTL_27;
diff --git a/ndctl/lib/private.h b/ndctl/lib/private.h
index e5c56295556d..46bc8908bd90 100644
--- a/ndctl/lib/private.h
+++ b/ndctl/lib/private.h
@@ -163,6 +163,7 @@ struct ndctl_bus {
 	int regions_init;
 	int has_nfit;
 	int has_of_node;
+	int has_cxl;
 	char *bus_path;
 	char *bus_buf;
 	size_t buf_len;
diff --git a/ndctl/libndctl.h b/ndctl/libndctl.h
index c52e82a6f826..91ef0f42f654 100644
--- a/ndctl/libndctl.h
+++ b/ndctl/libndctl.h
@@ -133,6 +133,7 @@ struct ndctl_bus *ndctl_bus_get_next(struct ndctl_bus *bus);
 struct ndctl_ctx *ndctl_bus_get_ctx(struct ndctl_bus *bus);
 int ndctl_bus_has_nfit(struct ndctl_bus *bus);
 int ndctl_bus_has_of_node(struct ndctl_bus *bus);
+int ndctl_bus_has_cxl(struct ndctl_bus *bus);
 int ndctl_bus_is_papr_scm(struct ndctl_bus *bus);
 unsigned int ndctl_bus_get_major(struct ndctl_bus *bus);
 unsigned int ndctl_bus_get_minor(struct ndctl_bus *bus);