[PATCH] nvme-pci: expose active quirks in sysfs

[Chaitanya Kulkarni]

On 10/29/25 23:18, Maurizio Lombardi wrote:
> On Thu Oct 30, 2025 at 12:25 AM CET, Chaitanya Kulkarni wrote:
>> On 10/29/25 01:02, Maurizio Lombardi wrote:
>>> On Wed Oct 29, 2025 at 6:47 AM CET, Chaitanya Kulkarni wrote:
>>>> On 10/28/25 10:00, Maurizio Lombardi wrote:
>>>>> On Tue Oct 28, 2025 at 5:32 PM CET, Bart Van Assche wrote:
>>>>>> On 10/28/25 7:29 AM, Maurizio Lombardi wrote:
>>>>>>> Currently, there is no straightforward way for a user to inspect
>>>>>>> the quirks value from userspace.
>>>>>>> Add a new read-only sysfs attribute "quirks";
>>>>>>> reading this file will display the hexadecimal
>>>>>>> value of the ctrl->quirks bitmask for the given NVMe device.
>>>>>> This patch changes the constants in enum nvme_quirks from
>>>>>> kernel-internal constants into an ABI. I'm not sure that's what we
>>>>>> want.
>>>>> I understand your concern.
>>>>> I could respin it to export the names of the active quirks
>>>>> rather than the raw bitmask, if there is an interest in having
>>>>> this feature.
>>>>>
>>>>> Maurizio
>>>>>
>>>> question here: do we need to care about some kind of security before we
>>>> expose controller information that is internal to the driver ?
>>>> CAP_SYS_ADMIN ? -ck
>>> IMO I don't think it's an information that needs to be hidden.
>>> After all, any user could run "lscpi -nn", get the vendor and device
>>> id and cross-reference them with the pci table in the source code
>>> to get the enabled quirks, this sysfs entry would just make it faster.
>>>
>>> Maurizio
>> Yes it is definitely useful after only decoding :-
>>
>> linux-block (for-next) # cat /sys/class/nvme/nvme0/quirks
>> 0x0000000000040000
>>
>> Active quirks:
>>     BOGUS_NID
>> linux-block (for-next) #
> Ah you anticipated me, I was preparing a somewhat similar patch.
>
> ************************


how about something like this totally untested ?

drivers/nvme/host/pci.c | 64 +++++++++++++++++++++++++++++++++++++++++
  1 file changed, 64 insertions(+)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index c916176bd9f0..ea9904e2dbd9 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2497,6 +2497,69 @@ static ssize_t cmbsz_show(struct device *dev, 
struct device_attribute *attr,
  }
  static DEVICE_ATTR_RO(cmbsz);

+static const struct {
+    unsigned long quirk;
+    const char *name;
+} nvme_quirk_info[] = {
+    { NVME_QUIRK_STRIPE_SIZE,        "STRIPE_SIZE" },
+    { NVME_QUIRK_IDENTIFY_CNS,        "IDENTIFY_CNS" },
+    { NVME_QUIRK_DEALLOCATE_ZEROES,        "DEALLOCATE_ZEROES" },
+    { NVME_QUIRK_DELAY_BEFORE_CHK_RDY, "DELAY_BEFORE_CHK_RDY" },
+    { NVME_QUIRK_NO_APST,            "NO_APST" },
+    { NVME_QUIRK_NO_DEEPEST_PS,        "NO_DEEPEST_PS" },
+    { NVME_QUIRK_QDEPTH_ONE,        "QDEPTH_ONE" },
+    { NVME_QUIRK_MEDIUM_PRIO_SQ,        "MEDIUM_PRIO_SQ" },
+    { NVME_QUIRK_IGNORE_DEV_SUBNQN,        "IGNORE_DEV_SUBNQN" },
+    { NVME_QUIRK_DISABLE_WRITE_ZEROES, "DISABLE_WRITE_ZEROES" },
+    { NVME_QUIRK_SIMPLE_SUSPEND,        "SIMPLE_SUSPEND" },
+    { NVME_QUIRK_SINGLE_VECTOR,        "SINGLE_VECTOR" },
+    { NVME_QUIRK_128_BYTES_SQES,        "128_BYTES_SQES" },
+    { NVME_QUIRK_SHARED_TAGS,        "SHARED_TAGS" },
+    { NVME_QUIRK_NO_TEMP_THRESH_CHANGE, "NO_TEMP_THRESH_CHANGE" },
+    { NVME_QUIRK_NO_NS_DESC_LIST,        "NO_NS_DESC_LIST" },
+    { NVME_QUIRK_DMA_ADDRESS_BITS_48,    "DMA_ADDRESS_BITS_48" },
+    { NVME_QUIRK_SKIP_CID_GEN,        "SKIP_CID_GEN" },
+    { NVME_QUIRK_BOGUS_NID,            "BOGUS_NID" },
+    { NVME_QUIRK_NO_SECONDARY_TEMP_THRESH, "NO_SECONDARY_TEMP_THRESH" },
+    { NVME_QUIRK_FORCE_NO_SIMPLE_SUSPEND, "FORCE_NO_SIMPLE_SUSPEND" },
+    { NVME_QUIRK_BROKEN_MSI,        "BROKEN_MSI" },
+    { NVME_QUIRK_DMAPOOL_ALIGN_512,        "DMAPOOL_ALIGN_512" },
+};
+
+static int nvme_get_quirks_string(unsigned long quirks, char *buf, 
size_t buf_len)
+{
+    size_t len = 0;
+    int i;
+
+    if (!quirks) {
+        len = scnprintf(buf, buf_len, "No quirks enabled\n");
+        return len;
+    }
+
+    len += scnprintf(buf + len, buf_len - len, "Active quirks:\n");
+
+    for (i = 0; i < ARRAY_SIZE(nvme_quirk_info); i++) {
+        if (quirks & nvme_quirk_info[i].quirk)
+            len += scnprintf(buf + len, buf_len - len, " %s\n",
+                     nvme_quirk_info[i].name);
+    }
+
+    return len;
+}
+
+static ssize_t quirks_show(struct device *dev, struct device_attribute 
*attr,
+               char *buf)
+{
+    struct nvme_dev *ndev = to_nvme_dev(dev_get_drvdata(dev));
+    int len;
+
+    len = sysfs_emit(buf, "0x%016lx\n\n", ndev->ctrl.quirks);
+    len += nvme_get_quirks_string(ndev->ctrl.quirks, buf + len, 
PAGE_SIZE - len);
+
+    return len;
+}
+static DEVICE_ATTR_RO(quirks);
+
  static ssize_t hmb_show(struct device *dev, struct device_attribute *attr,
              char *buf)
  {
@@ -2557,6 +2620,7 @@ static struct attribute *nvme_pci_attrs[] = {
      &dev_attr_cmbloc.attr,
      &dev_attr_cmbsz.attr,
      &dev_attr_hmb.attr,
+    &dev_attr_quirks.attr,
      NULL,
  };

-- 
2.40.0