[RFC PATCH] nvmet: passthru: use Invalid Field, not Invalid Opcode, for unhandled Get/Set Features FIDs

[Marko Ahvenainen]

Hello all,

My first kernel patch, be gentle ;)

nvmet_passthru_get_set_features() rejects any FID that reaches its
default case - whether intentionally blocked (IRQ_COALESCE,
IRQ_CONFIG, HOST_MEM_BUF, SW_PROGRESS, RESV_MASK, RESV_PERSIST) or
simply unlisted (e.g. FID 0, unassigned by the spec) - with
NVME_SC_INVALID_OPCODE | NVME_STATUS_DNR. That's the wrong class: the
Get/Set Features opcode is always valid here, it's the FID that's
rejected, so NVME_SC_INVALID_FIELD is correct.

This surfaced while debugging why nvme-cli's "dump all known
features" mode (get-feature -f 0) completes against a native
controller but aborts over nvmet passthru: natively, FID 0 gets a
plain Invalid Field rejection (no DNR) that nvme-cli tolerates and
continues past; nvmet's Invalid Opcode + DNR is not tolerated the
same way.

Verified with this fix applied: get-feature -f 0 now enumerates every
FID over nvmet passthru (NVMe/TCP) without aborting early. The DNR
flag was not the obstacle - only the status class was.

This is a status-code fix only, not a policy change: Get/Set Features
FIDs are still intercepted at more than one layer before reaching
this function (nvmet_parse_admin_cmd()/nvmet_parse_passthru_admin_cmd()
already service ASYNC_EVENT, KATO, NUM_QUEUES, HOST_ID and FDP with
nvmet's own emulation), so native and passthru queries still won't
return identical results for every FID - only this early-abort
failure mode is fixed. I'd rather leave any broader forwarding-policy
change to a separate discussion.

Unrelated aside noticed while reading this code: the
NVME_FEAT_ASYNC_EVENT case (and propably some other) inside this
function is dead code, since the callers above already intercept
that FID before it can be reached.

Signed-off-by: Marko Ahvenainen <marko.ahvenainen@xxxxxxxxxxxxxxxxxxxxxx>
---
 drivers/nvme/target/passthru.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvme/target/passthru.c b/drivers/nvme/target/passthru.c
index e27f84e3cf2b..df1396081f87 100644
--- a/drivers/nvme/target/passthru.c
+++ b/drivers/nvme/target/passthru.c
@@ -483,7 +483,7 @@ static u16 nvmet_passthru_get_set_features(struct nvmet_req *req)
        case NVME_FEAT_RESV_PERSIST:
                /* No reservations, see nvmet_parse_passthru_io_cmd() */
        default:
-               return NVME_SC_INVALID_OPCODE | NVME_STATUS_DNR;
+               return NVME_SC_INVALID_FIELD | NVME_STATUS_DNR;
        }
 }

--
2.43.0

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