[PATCH v4] nvme: reject keep-alive passthrough on non-fabrics

[Keith Busch]

On Fri, May 22, 2026 at 12:26:39PM -0400, Chao Shi wrote:
> +/*
> + * Some Set Features commands change controller behaviour that the driver is
> + * not prepared to handle on every transport.  Reject such commands from
> + * userspace passthrough rather than letting them put the controller into a
> + * state the driver cannot deal with.  The list can be extended as other
> + * problematic features are identified.
> + */
> +static bool nvme_passthru_cmd_allowed(struct nvme_ctrl *ctrl,
> +				      struct nvme_ns *ns,
> +				      struct nvme_command *c)
> +{
> +	/*
> +	 * This only filters admin commands (ns == NULL).  I/O commands share
> +	 * the opcode space with admin commands - Dataset Management is 0x09,
> +	 * the same value as Set Features - so they must not be inspected here.
> +	 */
> +	if (ns || c->common.opcode != nvme_admin_set_features)
> +		return true;
> +
> +	switch (le32_to_cpu(c->common.cdw10) & 0xff) {
> +	case NVME_FEAT_KATO:
> +		/*
> +		 * Keep Alive is optional on PCIe (NVMe 2.0a 5.27.1.12) and the
> +		 * driver only arms keep-alive for fabrics.  Enabling it on
> +		 * other transports starts a keep-alive command the driver is
> +		 * not set up for and harms idle power states, so reject it.
> +		 */
> +		return ctrl->ops->flags & NVME_F_FABRICS;
> +	default:
> +		return true;
> +	}
> +}

This doesn't need to be its own function. You can add these checks to
the existing nvme_cmd_allowed():

---
@@ -50,6 +53,18 @@ static bool nvme_cmd_allowed(struct nvme_ns *ns, struct nvme_command *c,
                        case NVME_ID_CNS_CTRL:
                                return true;
                        }
+		} else if (c->common.opcode == nvme_admin_set_features) {
+			switch (cpu_to_le32(c->features.fid) & 0xff) {
+			case NVME_FEAT_KATO:
+				if (ctrl->ops->flags & NVME_F_FABRICS)
+					break;
+				fallthrough;
+			case NVME_FEAT_HOST_BEHAVIOR:
+			case NVME_FEAT_HOST_MEM_BUF:
+			case NVME_FEAT_NUM_QUEUES:
+			case NVME_FEAT_AUTO_PST:
+				return false;
+			}
                }
                goto admin;
        }
--