[PATCH V2] nvme: expose active quirks in sysfs

[John Meneghini]

Reviewed-by: John Meneghini <jmeneghi at redhat.com>
Tested-by: John Meneghini <jmeneghi at redhat.com>

Looks good to me. Testing this on my VM shows the correct quirk information for both

   -device nvme,use-intel-id=on and
   -device nvme,use-intel-id=off

root at target-vm:~# grep . /sys/class/nvme/nvme0/quirk* /sys/class/nvme/nvme0/device/{vendor,device}
/sys/class/nvme/nvme0/quirks:0x00040202
/sys/class/nvme/nvme0/device/vendor:0x8086
/sys/class/nvme/nvme0/device/device:0x5845
root at target-vm:~# grep . /sys/class/nvme/nvme1/quirk* /sys/class/nvme/nvme1/device/{vendor,device}
/sys/class/nvme/nvme1/quirks:0x00040000
/sys/class/nvme/nvme1/device/vendor:0x1b36
/sys/class/nvme/nvme1/device/device:0x0010

Keith, please merge this patch.

/John

On 11/3/25 9:44 AM, Maurizio Lombardi wrote:
> Currently, there is no straightforward way for a user to inspect
> which quirks are active for a given device from userspace.
> 
> Add a new "quirks" sysfs attribute to the nvme controller device.
> 
> Reading this file will display a human-readable list
> of all active quirks, with each quirk name on a new line.
> If no quirks are active, it will display "none".
> 
> Signed-off-by: Maurizio Lombardi <mlombard at redhat.com>
> ---
> 
> V2: Do not expose kernel-internal constants to userspace.
>      Move the quirks attribute to the controller device, where it belongs.
> 
>   drivers/nvme/host/nvme.h  | 54 +++++++++++++++++++++++++++++++++++++++
>   drivers/nvme/host/sysfs.c | 23 +++++++++++++++++
>   2 files changed, 77 insertions(+)
> 
> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
> index 102fae6a231c..647f19dd57e9 100644
> --- a/drivers/nvme/host/nvme.h
> +++ b/drivers/nvme/host/nvme.h
> @@ -180,6 +180,60 @@ enum nvme_quirks {
>   	NVME_QUIRK_DMAPOOL_ALIGN_512		= (1 << 22),
>   };
>   
> +static inline char *nvme_quirk_name(enum nvme_quirks q)
> +{
> +	switch (q) {
> +	case NVME_QUIRK_STRIPE_SIZE:
> +		return "stripe_size";
> +	case NVME_QUIRK_IDENTIFY_CNS:
> +		return "identify_cns";
> +	case NVME_QUIRK_DEALLOCATE_ZEROES:
> +		return "deallocate_zeroes";
> +	case NVME_QUIRK_DELAY_BEFORE_CHK_RDY:
> +		return "delay_before_chk_rdy";
> +	case NVME_QUIRK_NO_APST:
> +		return "no_apst";
> +	case NVME_QUIRK_NO_DEEPEST_PS:
> +		return "no_deepest_ps";
> +	case NVME_QUIRK_QDEPTH_ONE:
> +		return "qdepth_one";
> +	case NVME_QUIRK_MEDIUM_PRIO_SQ:
> +		return "medium_prio_sq";
> +	case NVME_QUIRK_IGNORE_DEV_SUBNQN:
> +		return "ignore_dev_subnqn";
> +	case NVME_QUIRK_DISABLE_WRITE_ZEROES:
> +		return "disable_write_zeroes";
> +	case NVME_QUIRK_SIMPLE_SUSPEND:
> +		return "simple_suspend";
> +	case NVME_QUIRK_SINGLE_VECTOR:
> +		return "single_vector";
> +	case NVME_QUIRK_128_BYTES_SQES:
> +		return "128_bytes_sqes";
> +	case NVME_QUIRK_SHARED_TAGS:
> +		return "shared_tags";
> +	case NVME_QUIRK_NO_TEMP_THRESH_CHANGE:
> +		return "no_temp_thresh_change";
> +	case NVME_QUIRK_NO_NS_DESC_LIST:
> +		return "no_ns_desc_list";
> +	case NVME_QUIRK_DMA_ADDRESS_BITS_48:
> +		return "dma_address_bits_48";
> +	case NVME_QUIRK_SKIP_CID_GEN:
> +		return "skip_cid_gen";
> +	case NVME_QUIRK_BOGUS_NID:
> +		return "bogus_nid";
> +	case NVME_QUIRK_NO_SECONDARY_TEMP_THRESH:
> +		return "no_secondary_temp_thresh";
> +	case NVME_QUIRK_FORCE_NO_SIMPLE_SUSPEND:
> +		return "force_no_simple_suspend";
> +	case NVME_QUIRK_BROKEN_MSI:
> +		return "broken_msi";
> +	case NVME_QUIRK_DMAPOOL_ALIGN_512:
> +		return "dmapool_align_512";
> +	}
> +
> +	return "unknown";
> +}
> +
>   /*
>    * Common request structure for NVMe passthrough.  All drivers must have
>    * this structure as the first member of their request-private data.
> diff --git a/drivers/nvme/host/sysfs.c b/drivers/nvme/host/sysfs.c
> index 29430949ce2f..16c6fea4b2db 100644
> --- a/drivers/nvme/host/sysfs.c
> +++ b/drivers/nvme/host/sysfs.c
> @@ -601,6 +601,28 @@ static ssize_t dctype_show(struct device *dev,
>   }
>   static DEVICE_ATTR_RO(dctype);
>   
> +static ssize_t quirks_show(struct device *dev, struct device_attribute *attr,
> +                char *buf)
> +{
> +	int count = 0, i;
> +	struct nvme_ctrl *ctrl = dev_get_drvdata(dev);
> +	unsigned long quirks = ctrl->quirks;
> +
> +	if (!quirks)
> +		return sysfs_emit(buf, "none\n");
> +
> +	for (i = 0; quirks; ++i) {
> +		if (quirks & 1) {
> +			count += sysfs_emit_at(buf, count, "%s\n",
> +					nvme_quirk_name(BIT(i)));
> +		}
> +		quirks >>= 1;
> +	}
> +
> +	return count;
> +}
> +static DEVICE_ATTR_RO(quirks);
> +
>   #ifdef CONFIG_NVME_HOST_AUTH
>   static ssize_t nvme_ctrl_dhchap_secret_show(struct device *dev,
>   		struct device_attribute *attr, char *buf)
> @@ -742,6 +764,7 @@ static struct attribute *nvme_dev_attrs[] = {
>   	&dev_attr_kato.attr,
>   	&dev_attr_cntrltype.attr,
>   	&dev_attr_dctype.attr,
> +	&dev_attr_quirks.attr,
>   #ifdef CONFIG_NVME_HOST_AUTH
>   	&dev_attr_dhchap_secret.attr,
>   	&dev_attr_dhchap_ctrl_secret.attr,