path: root/0005-nvme-Fix-namespace-identifiers.patch

From b25fd9caca9b2fb34e5a4d7d4bee0031e4758d0a Mon Sep 17 00:00:00 2001
From: Tomas Bzatek <tbzatek@redhat.com>
Date: Thu, 22 Sep 2022 16:31:28 +0200
Subject: [PATCH 1/5] nvme: Avoid sending NVME_IDENTIFY_CNS_NS_DESC_LIST on
 older devices

Turned out this Identify feature was introduced only with the NVMe 1.3
specification. To find out device supported NVMe revision an extra
Identify Controller call is needed.
---
 src/plugins/nvme/nvme-info.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/plugins/nvme/nvme-info.c b/src/plugins/nvme/nvme-info.c
index fdd90459..112b4054 100644
--- a/src/plugins/nvme/nvme-info.c
+++ b/src/plugins/nvme/nvme-info.c
@@ -431,7 +431,7 @@ BDNVMEControllerInfo * bd_nvme_get_controller_info (const gchar *device, GError
     if (fd < 0)
         return NULL;
 
-    /* send the NVME_IDENTIFY_CNS_NS + NVME_IDENTIFY_CNS_CTRL ioctl */
+    /* send the NVME_IDENTIFY_CNS_CTRL ioctl */
     ret = nvme_identify_ctrl (fd, &ctrl_id);
     if (ret != 0) {
         _nvme_status_to_error (ret, FALSE, error);
@@ -539,9 +539,11 @@ BDNVMEControllerInfo * bd_nvme_get_controller_info (const gchar *device, GError
  */
 BDNVMENamespaceInfo *bd_nvme_get_namespace_info (const gchar *device, GError **error) {
     int ret;
-    int ret_desc;
+    int ret_ctrl;
+    int ret_desc = -1;
     int fd;
     __u32 nsid = 0;
+    struct nvme_id_ctrl ctrl_id = ZERO_INIT;
     struct nvme_id_ns ns_info = ZERO_INIT;
     uint8_t desc[NVME_IDENTIFY_DATA_SIZE] = ZERO_INIT;
     guint8 flbas;
@@ -565,7 +567,6 @@ BDNVMENamespaceInfo *bd_nvme_get_namespace_info (const gchar *device, GError **e
     }
 
     /* send the NVME_IDENTIFY_CNS_NS ioctl */
-    ret_desc = nvme_identify_ns_descs (fd, nsid, (struct nvme_ns_id_desc *) &desc);
     ret = nvme_identify_ns (fd, nsid, &ns_info);
     if (ret != 0) {
         _nvme_status_to_error (ret, FALSE, error);
@@ -573,6 +574,13 @@ BDNVMENamespaceInfo *bd_nvme_get_namespace_info (const gchar *device, GError **e
         close (fd);
         return NULL;
     }
+
+    /* send the NVME_IDENTIFY_CNS_CTRL ioctl */
+    ret_ctrl = nvme_identify_ctrl (fd, &ctrl_id);
+
+    /* send the NVME_IDENTIFY_CNS_NS_DESC_LIST ioctl, NVMe 1.3 */
+    if (ret_ctrl == 0 && GUINT32_FROM_LE (ctrl_id.ver) >= 0x10300)
+        ret_desc = nvme_identify_ns_descs (fd, nsid, (struct nvme_ns_id_desc *) &desc);
     close (fd);
 
     info = g_new0 (BDNVMENamespaceInfo, 1);
-- 
2.39.0


From e6f7d0c4562623b03df96dc6b89ab00d8e4d6b90 Mon Sep 17 00:00:00 2001
From: Tomas Bzatek <tbzatek@redhat.com>
Date: Thu, 22 Sep 2022 16:56:26 +0200
Subject: [PATCH 2/5] nvme: Add BD_NVME_NS_FEAT_ROTATIONAL

A NVMe 2.0 feature indicating rotational medium on a namespace level.
Further information can be found in the Rotational Media Information Log
page (Log Identifier 16h) that is not implemented in libblockdev yet.
---
 src/lib/plugin_apis/nvme.api |  2 ++
 src/plugins/nvme/nvme-info.c | 10 ++++++++++
 src/plugins/nvme/nvme.h      |  2 ++
 tests/nvme_test.py           |  1 +
 4 files changed, 15 insertions(+)

diff --git a/src/lib/plugin_apis/nvme.api b/src/lib/plugin_apis/nvme.api
index 79247a01..7bc2cf9e 100644
--- a/src/lib/plugin_apis/nvme.api
+++ b/src/lib/plugin_apis/nvme.api
@@ -317,12 +317,14 @@ GType bd_nvme_lba_format_get_type () {
  *                                    in the NVM subsystem concurrently.
  * @BD_NVME_NS_FEAT_FORMAT_PROGRESS: indicates the capability to report the percentage of the namespace
  *                                   that remains to be formatted.
+ * @BD_NVME_NS_FEAT_ROTATIONAL: indicates a rotational medium.
  */
 /* BpG-skip-end */
 typedef enum {
     BD_NVME_NS_FEAT_THIN             = 1 << 0,
     BD_NVME_NS_FEAT_MULTIPATH_SHARED = 1 << 1,
     BD_NVME_NS_FEAT_FORMAT_PROGRESS  = 1 << 2,
+    BD_NVME_NS_FEAT_ROTATIONAL       = 1 << 3,
 } BDNVMENamespaceFeature;
 
 #define BD_NVME_TYPE_NAMESPACE_INFO (bd_nvme_namespace_info_get_type ())
diff --git a/src/plugins/nvme/nvme-info.c b/src/plugins/nvme/nvme-info.c
index 112b4054..c574a6f3 100644
--- a/src/plugins/nvme/nvme-info.c
+++ b/src/plugins/nvme/nvme-info.c
@@ -541,10 +541,12 @@ BDNVMENamespaceInfo *bd_nvme_get_namespace_info (const gchar *device, GError **e
     int ret;
     int ret_ctrl;
     int ret_desc = -1;
+    int ret_ns_ind = -1;
     int fd;
     __u32 nsid = 0;
     struct nvme_id_ctrl ctrl_id = ZERO_INIT;
     struct nvme_id_ns ns_info = ZERO_INIT;
+    struct nvme_id_independent_id_ns ns_info_ind = ZERO_INIT;
     uint8_t desc[NVME_IDENTIFY_DATA_SIZE] = ZERO_INIT;
     guint8 flbas;
     guint i;
@@ -581,6 +583,10 @@ BDNVMENamespaceInfo *bd_nvme_get_namespace_info (const gchar *device, GError **e
     /* send the NVME_IDENTIFY_CNS_NS_DESC_LIST ioctl, NVMe 1.3 */
     if (ret_ctrl == 0 && GUINT32_FROM_LE (ctrl_id.ver) >= 0x10300)
         ret_desc = nvme_identify_ns_descs (fd, nsid, (struct nvme_ns_id_desc *) &desc);
+
+    /* send the NVME_IDENTIFY_CNS_CSI_INDEPENDENT_ID_NS ioctl, NVMe 2.0 */
+    if (ret_ctrl == 0 && GUINT32_FROM_LE (ctrl_id.ver) >= 0x20000)
+        ret_ns_ind = nvme_identify_independent_identify_ns (fd, nsid, &ns_info_ind);
     close (fd);
 
     info = g_new0 (BDNVMENamespaceInfo, 1);
@@ -627,6 +633,10 @@ BDNVMENamespaceInfo *bd_nvme_get_namespace_info (const gchar *device, GError **e
             }
         }
     }
+    if (ret_ns_ind == 0) {
+        if ((ns_info_ind.nsfeat & 1 << 4) == 1 << 4)
+            info->features |= BD_NVME_NS_FEAT_ROTATIONAL;
+    }
 
     /* translate the LBA Format array */
     ptr_array = g_ptr_array_new ();
diff --git a/src/plugins/nvme/nvme.h b/src/plugins/nvme/nvme.h
index a7d30d79..ad456a82 100644
--- a/src/plugins/nvme/nvme.h
+++ b/src/plugins/nvme/nvme.h
@@ -202,11 +202,13 @@ typedef struct BDNVMELBAFormat {
  *                                    in the NVM subsystem concurrently.
  * @BD_NVME_NS_FEAT_FORMAT_PROGRESS: indicates the capability to report the percentage of the namespace
  *                                   that remains to be formatted.
+ * @BD_NVME_NS_FEAT_ROTATIONAL: indicates a rotational medium.
  */
 typedef enum {
     BD_NVME_NS_FEAT_THIN             = 1 << 0,
     BD_NVME_NS_FEAT_MULTIPATH_SHARED = 1 << 1,
     BD_NVME_NS_FEAT_FORMAT_PROGRESS  = 1 << 2,
+    BD_NVME_NS_FEAT_ROTATIONAL       = 1 << 3,
 } BDNVMENamespaceFeature;
 
 /**
diff --git a/tests/nvme_test.py b/tests/nvme_test.py
index a46f7422..f205e539 100644
--- a/tests/nvme_test.py
+++ b/tests/nvme_test.py
@@ -73,6 +73,7 @@ class NVMeTestCase(NVMeTest):
         self.assertFalse(info.features & BlockDev.NVMENamespaceFeature.THIN)
         self.assertTrue (info.features & BlockDev.NVMENamespaceFeature.MULTIPATH_SHARED)
         self.assertFalse(info.features & BlockDev.NVMENamespaceFeature.FORMAT_PROGRESS)
+        self.assertFalse(info.features & BlockDev.NVMENamespaceFeature.ROTATIONAL)
         self.assertEqual(info.eui64, "0000000000000000")
         self.assertEqual(info.format_progress_remaining, 0)
         self.assertEqual(len(info.lba_formats), 1)
-- 
2.39.0


From 4ff0df937dcd357623e7b7d960c08c476b1deffb Mon Sep 17 00:00:00 2001
From: Tomas Bzatek <tbzatek@redhat.com>
Date: Fri, 9 Dec 2022 16:13:43 +0100
Subject: [PATCH 3/5] nvme: Fix namespace identifiers

Use Namespace Identification Descriptor list (CNS 03h) data when available
and NVM Command Set Identify Namespace Data Structure (CNS 00h) as a fallback.

Also, if the CNS 00h EUI64 or NGUID fields equal to zero, return NULL
instead of zeroes:
  "If the controller is not able to provide a ... identifier in this field,
   then this field shall be cleared to 0h."
---
 src/plugins/nvme/nvme-info.c | 26 +++++++++++++++++++-------
 tests/nvme_test.py           |  2 +-
 2 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/src/plugins/nvme/nvme-info.c b/src/plugins/nvme/nvme-info.c
index c574a6f3..ac189abe 100644
--- a/src/plugins/nvme/nvme-info.c
+++ b/src/plugins/nvme/nvme-info.c
@@ -603,12 +603,7 @@ BDNVMENamespaceInfo *bd_nvme_get_namespace_info (const gchar *device, GError **e
     info->format_progress_remaining = ns_info.fpi & NVME_NS_FPI_REMAINING;
     /* TODO: what the ns_info.nvmcap really stands for? */
     info->write_protected = (ns_info.nsattr & NVME_NS_NSATTR_WRITE_PROTECTED) == NVME_NS_NSATTR_WRITE_PROTECTED;
-    info->nguid = g_malloc0 (sizeof (ns_info.nguid) * 2 + 1);
-    for (i = 0; i < G_N_ELEMENTS (ns_info.nguid); i++)
-        snprintf (info->nguid + i * 2, 3, "%02x", ns_info.nguid[i]);
-    info->eui64 = g_malloc0 (sizeof (ns_info.eui64) * 2 + 1);
-    for (i = 0; i < G_N_ELEMENTS (ns_info.eui64); i++)
-        snprintf (info->eui64 + i * 2, 3, "%02x", ns_info.eui64[i]);
+
     if (ret_desc == 0) {
         for (i = 0; i < NVME_IDENTIFY_DATA_SIZE; i += len) {
             struct nvme_ns_id_desc *d = (void *) desc + i;
@@ -620,8 +615,14 @@ BDNVMENamespaceInfo *bd_nvme_get_namespace_info (const gchar *device, GError **e
 
             switch (d->nidt) {
                 case NVME_NIDT_EUI64:
+                    info->eui64 = g_malloc0 (d->nidl * 2 + 1);
+                    for (i = 0; i < d->nidl; i++)
+                        snprintf (info->eui64 + i * 2, 3, "%02x", d->nid[i]);
+                    break;
                 case NVME_NIDT_NGUID:
-                    /* already have these from nvme_identify_ns() */
+                    info->nguid = g_malloc0 (d->nidl * 2 + 1);
+                    for (i = 0; i < d->nidl; i++)
+                        snprintf (info->nguid + i * 2, 3, "%02x", d->nid[i]);
                     break;
                 case NVME_NIDT_UUID:
                     uuid_unparse (d->nid, uuid_buf);
@@ -633,6 +634,17 @@ BDNVMENamespaceInfo *bd_nvme_get_namespace_info (const gchar *device, GError **e
             }
         }
     }
+
+    if (info->nguid == NULL && ns_info.nguid[G_N_ELEMENTS (ns_info.nguid) - 1] > 0) {
+        info->nguid = g_malloc0 (sizeof (ns_info.nguid) * 2 + 1);
+        for (i = 0; i < G_N_ELEMENTS (ns_info.nguid); i++)
+            snprintf (info->nguid + i * 2, 3, "%02x", ns_info.nguid[i]);
+    }
+    if (info->eui64 == NULL && ns_info.eui64[G_N_ELEMENTS (ns_info.eui64) - 1] > 0) {
+        info->eui64 = g_malloc0 (sizeof (ns_info.eui64) * 2 + 1);
+        for (i = 0; i < G_N_ELEMENTS (ns_info.eui64); i++)
+            snprintf (info->eui64 + i * 2, 3, "%02x", ns_info.eui64[i]);
+    }
     if (ret_ns_ind == 0) {
         if ((ns_info_ind.nsfeat & 1 << 4) == 1 << 4)
             info->features |= BD_NVME_NS_FEAT_ROTATIONAL;
diff --git a/tests/nvme_test.py b/tests/nvme_test.py
index f205e539..a1822be6 100644
--- a/tests/nvme_test.py
+++ b/tests/nvme_test.py
@@ -74,7 +74,7 @@ class NVMeTestCase(NVMeTest):
         self.assertTrue (info.features & BlockDev.NVMENamespaceFeature.MULTIPATH_SHARED)
         self.assertFalse(info.features & BlockDev.NVMENamespaceFeature.FORMAT_PROGRESS)
         self.assertFalse(info.features & BlockDev.NVMENamespaceFeature.ROTATIONAL)
-        self.assertEqual(info.eui64, "0000000000000000")
+        self.assertIsNone(info.eui64)
         self.assertEqual(info.format_progress_remaining, 0)
         self.assertEqual(len(info.lba_formats), 1)
         self.assertGreater(len(info.nguid), 0)
-- 
2.39.0


From cdbb9a37a19d3f388910f68c4c384bafae8901ae Mon Sep 17 00:00:00 2001
From: Tomas Bzatek <tbzatek@redhat.com>
Date: Wed, 11 Jan 2023 18:19:36 +0100
Subject: [PATCH 4/5] nvme: Use libnvme-1.2's nvme_uuid_to_string()

This also bumps libnvme dependency to 1.2
---
 configure.ac                    |  5 +----
 src/plugins/nvme/Makefile.am    |  4 ++--
 src/plugins/nvme/nvme-error.c   |  3 ---
 src/plugins/nvme/nvme-fabrics.c |  1 -
 src/plugins/nvme/nvme-info.c    | 17 ++++++++++-------
 src/plugins/nvme/nvme-op.c      |  1 -
 src/plugins/nvme/nvme.c         |  1 -
 7 files changed, 13 insertions(+), 19 deletions(-)

diff --git a/configure.ac b/configure.ac
index ec789c91..fbd70473 100644
--- a/configure.ac
+++ b/configure.ac
@@ -281,10 +281,7 @@ AS_IF([test "x$with_nvdimm" != "xno"],
       [])
 
 AS_IF([test "x$with_nvme" != "xno"],
-      [LIBBLOCKDEV_PKG_CHECK_MODULES([NVME], [libnvme >= 1.0])
-      AS_IF([$PKG_CONFIG --atleast-version=1.1 libnvme],
-            [AC_DEFINE([HAVE_LIBNVME_1_1])], [])
-      ],
+      [LIBBLOCKDEV_PKG_CHECK_MODULES([NVME], [libnvme >= 1.2])],
       [])
 
 AS_IF([test "x$with_vdo" != "xno"],
diff --git a/src/plugins/nvme/Makefile.am b/src/plugins/nvme/Makefile.am
index b4a10ce0..a8a856d4 100644
--- a/src/plugins/nvme/Makefile.am
+++ b/src/plugins/nvme/Makefile.am
@@ -2,8 +2,8 @@ AUTOMAKE_OPTIONS = subdir-objects
 
 lib_LTLIBRARIES = libbd_nvme.la
 
-libbd_nvme_la_CFLAGS = $(GLIB_CFLAGS) $(GIO_CFLAGS) $(UUID_CFLAGS) $(NVME_CFLAGS) -Wall -Wextra -Werror
-libbd_nvme_la_LIBADD = ${builddir}/../../utils/libbd_utils.la $(GLIB_LIBS) $(GIO_LIBS) $(UUID_LIBS) $(NVME_LIBS)
+libbd_nvme_la_CFLAGS = $(GLIB_CFLAGS) $(GIO_CFLAGS) $(NVME_CFLAGS) -Wall -Wextra -Werror
+libbd_nvme_la_LIBADD = ${builddir}/../../utils/libbd_utils.la $(GLIB_LIBS) $(GIO_LIBS) $(NVME_LIBS)
 libbd_nvme_la_LDFLAGS = -L${srcdir}/../../utils/ -version-info 2:0:0 -Wl,--no-undefined
 libbd_nvme_la_CPPFLAGS = -I${builddir}/../../../include/ -I${srcdir}/../ -I. -DPACKAGE_SYSCONF_DIR=\""$(sysconfdir)"\"
 
diff --git a/src/plugins/nvme/nvme-error.c b/src/plugins/nvme/nvme-error.c
index 86f0d6a3..cb95a46d 100644
--- a/src/plugins/nvme/nvme-error.c
+++ b/src/plugins/nvme/nvme-error.c
@@ -28,7 +28,6 @@
 #include <malloc.h>
 
 #include <libnvme.h>
-#include <uuid/uuid.h>
 
 #include <blockdev/utils.h>
 #include <check_deps.h>
@@ -123,7 +122,6 @@ void _nvme_fabrics_errno_to_gerror (int result, int _errno, GError **error)
             case ENVME_CONNECT_LOOKUP_SUBSYS:
                 code = BD_NVME_ERROR_CONNECT;
                 break;
-#ifdef HAVE_LIBNVME_1_1
             case ENVME_CONNECT_ALREADY:
                 code = BD_NVME_ERROR_CONNECT_ALREADY;
                 break;
@@ -139,7 +137,6 @@ void _nvme_fabrics_errno_to_gerror (int result, int _errno, GError **error)
             case ENVME_CONNECT_OPNOTSUPP:
                 code = BD_NVME_ERROR_CONNECT_OPNOTSUPP;
                 break;
-#endif
             default:
                 code = BD_NVME_ERROR_CONNECT;
         }
diff --git a/src/plugins/nvme/nvme-fabrics.c b/src/plugins/nvme/nvme-fabrics.c
index 20ed57f5..bba7392d 100644
--- a/src/plugins/nvme/nvme-fabrics.c
+++ b/src/plugins/nvme/nvme-fabrics.c
@@ -30,7 +30,6 @@
 #include <glib/gstdio.h>
 
 #include <libnvme.h>
-#include <uuid/uuid.h>
 
 #include <blockdev/utils.h>
 #include <check_deps.h>
diff --git a/src/plugins/nvme/nvme-info.c b/src/plugins/nvme/nvme-info.c
index ac189abe..18719d51 100644
--- a/src/plugins/nvme/nvme-info.c
+++ b/src/plugins/nvme/nvme-info.c
@@ -28,7 +28,6 @@
 #include <malloc.h>
 
 #include <libnvme.h>
-#include <uuid/uuid.h>
 
 #include <blockdev/utils.h>
 #include <check_deps.h>
@@ -408,6 +407,14 @@ static gchar *decode_nvme_rev (guint32 ver) {
         return g_strdup_printf ("%u.%u.%u", mjr, mnr, ter);
 }
 
+static gchar *_uuid_to_str (unsigned char uuid[NVME_UUID_LEN]) {
+    gchar uuid_buf[NVME_UUID_LEN_STRING] = ZERO_INIT;
+
+    if (nvme_uuid_to_string (uuid, uuid_buf) == 0)
+        return g_strdup (uuid_buf);
+    return NULL;
+}
+
 /**
  * bd_nvme_get_controller_info:
  * @device: a NVMe controller device (e.g. `/dev/nvme0`)
@@ -461,9 +468,7 @@ BDNVMEControllerInfo * bd_nvme_get_controller_info (const gchar *device, GError
     info->pci_vendor_id = GUINT16_FROM_LE (ctrl_id.vid);
     info->pci_subsys_vendor_id = GUINT16_FROM_LE (ctrl_id.ssvid);
     info->ctrl_id = GUINT16_FROM_LE (ctrl_id.cntlid);
-    /* TODO: decode fguid as 128-bit hex string? */
-    info->fguid = g_strdup_printf ("%-.*s", (int) sizeof (ctrl_id.fguid), ctrl_id.fguid);
-    g_strstrip (info->fguid);
+    info->fguid = _uuid_to_str (ctrl_id.fguid);
     info->model_number = g_strndup (ctrl_id.mn, sizeof (ctrl_id.mn));
     g_strstrip (info->model_number);
     info->serial_number = g_strndup (ctrl_id.sn, sizeof (ctrl_id.sn));
@@ -607,7 +612,6 @@ BDNVMENamespaceInfo *bd_nvme_get_namespace_info (const gchar *device, GError **e
     if (ret_desc == 0) {
         for (i = 0; i < NVME_IDENTIFY_DATA_SIZE; i += len) {
             struct nvme_ns_id_desc *d = (void *) desc + i;
-            gchar uuid_buf[37] = ZERO_INIT;
 
             if (!d->nidl)
                 break;
@@ -625,8 +629,7 @@ BDNVMENamespaceInfo *bd_nvme_get_namespace_info (const gchar *device, GError **e
                         snprintf (info->nguid + i * 2, 3, "%02x", d->nid[i]);
                     break;
                 case NVME_NIDT_UUID:
-                    uuid_unparse (d->nid, uuid_buf);
-                    info->uuid = g_strdup (uuid_buf);
+                    info->uuid = _uuid_to_str (d->nid);
                     break;
                 case NVME_NIDT_CSI:
                     /* unused */
diff --git a/src/plugins/nvme/nvme-op.c b/src/plugins/nvme/nvme-op.c
index 4568c453..c9e92697 100644
--- a/src/plugins/nvme/nvme-op.c
+++ b/src/plugins/nvme/nvme-op.c
@@ -29,7 +29,6 @@
 #include <linux/fs.h>
 
 #include <libnvme.h>
-#include <uuid/uuid.h>
 
 #include <blockdev/utils.h>
 #include <check_deps.h>
diff --git a/src/plugins/nvme/nvme.c b/src/plugins/nvme/nvme.c
index 00f2f76e..4a32ac4e 100644
--- a/src/plugins/nvme/nvme.c
+++ b/src/plugins/nvme/nvme.c
@@ -28,7 +28,6 @@
 #include <malloc.h>
 
 #include <libnvme.h>
-#include <uuid/uuid.h>
 
 #include <blockdev/utils.h>
 #include <check_deps.h>
-- 
2.39.0


From 64263599ec39b6b0f20d8e16c1169afcf66f5d9a Mon Sep 17 00:00:00 2001
From: Tomas Bzatek <tbzatek@redhat.com>
Date: Thu, 12 Jan 2023 16:01:28 +0100
Subject: [PATCH 5/5] nvme: Fix zeroed struct fields detection

As often stated in the NVMe specification, fields of features that
are either not implemented or not valid are typically cleared to zero (0h).
---
 src/plugins/nvme/nvme-info.c | 20 +++++++++++++++-----
 tests/nvme_test.py           |  2 +-
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/src/plugins/nvme/nvme-info.c b/src/plugins/nvme/nvme-info.c
index 18719d51..85f94a32 100644
--- a/src/plugins/nvme/nvme-info.c
+++ b/src/plugins/nvme/nvme-info.c
@@ -415,6 +415,15 @@ static gchar *_uuid_to_str (unsigned char uuid[NVME_UUID_LEN]) {
     return NULL;
 }
 
+static gboolean _nvme_a_is_zero (const __u8 a[], int len) {
+    int i;
+
+    for (i = 0; i < len; i++)
+        if (a[i] > 0)
+            return FALSE;
+    return TRUE;
+}
+
 /**
  * bd_nvme_get_controller_info:
  * @device: a NVMe controller device (e.g. `/dev/nvme0`)
@@ -468,7 +477,8 @@ BDNVMEControllerInfo * bd_nvme_get_controller_info (const gchar *device, GError
     info->pci_vendor_id = GUINT16_FROM_LE (ctrl_id.vid);
     info->pci_subsys_vendor_id = GUINT16_FROM_LE (ctrl_id.ssvid);
     info->ctrl_id = GUINT16_FROM_LE (ctrl_id.cntlid);
-    info->fguid = _uuid_to_str (ctrl_id.fguid);
+    if (!_nvme_a_is_zero (ctrl_id.fguid, sizeof (ctrl_id.fguid)))
+        info->fguid = _uuid_to_str (ctrl_id.fguid);
     info->model_number = g_strndup (ctrl_id.mn, sizeof (ctrl_id.mn));
     g_strstrip (info->model_number);
     info->serial_number = g_strndup (ctrl_id.sn, sizeof (ctrl_id.sn));
@@ -638,14 +648,14 @@ BDNVMENamespaceInfo *bd_nvme_get_namespace_info (const gchar *device, GError **e
         }
     }
 
-    if (info->nguid == NULL && ns_info.nguid[G_N_ELEMENTS (ns_info.nguid) - 1] > 0) {
+    if (info->nguid == NULL && !_nvme_a_is_zero (ns_info.nguid, sizeof (ns_info.nguid))) {
         info->nguid = g_malloc0 (sizeof (ns_info.nguid) * 2 + 1);
-        for (i = 0; i < G_N_ELEMENTS (ns_info.nguid); i++)
+        for (i = 0; i < sizeof (ns_info.nguid); i++)
             snprintf (info->nguid + i * 2, 3, "%02x", ns_info.nguid[i]);
     }
-    if (info->eui64 == NULL && ns_info.eui64[G_N_ELEMENTS (ns_info.eui64) - 1] > 0) {
+    if (info->eui64 == NULL && !_nvme_a_is_zero (ns_info.eui64, sizeof (ns_info.eui64))) {
         info->eui64 = g_malloc0 (sizeof (ns_info.eui64) * 2 + 1);
-        for (i = 0; i < G_N_ELEMENTS (ns_info.eui64); i++)
+        for (i = 0; i < sizeof (ns_info.eui64); i++)
             snprintf (info->eui64 + i * 2, 3, "%02x", ns_info.eui64[i]);
     }
     if (ret_ns_ind == 0) {
diff --git a/tests/nvme_test.py b/tests/nvme_test.py
index a1822be6..a1494d9a 100644
--- a/tests/nvme_test.py
+++ b/tests/nvme_test.py
@@ -116,7 +116,7 @@ class NVMeTestCase(NVMeTest):
         self.assertFalse(info.features & BlockDev.NVMEControllerFeature.ENCLOSURE)
         self.assertFalse(info.features & BlockDev.NVMEControllerFeature.MGMT_PCIE)
         self.assertFalse(info.features & BlockDev.NVMEControllerFeature.MGMT_SMBUS)
-        self.assertEqual(info.fguid, "")
+        self.assertIsNone(info.fguid)
         self.assertEqual(info.pci_vendor_id, 0)
         self.assertEqual(info.pci_subsys_vendor_id, 0)
         self.assertIn("Linux", info.model_number)
-- 
2.39.0