iflib: Prevent kernel panic caused by loading driver with a specific interrupt configuration

If a device has only 1 MSI-X interrupt available and does not support either
MSI or legacy interrupts, iflib_device_register() will fail, leak memory and
MSI resources, and the driver will not load. Worse, if another iflib-using
driver tries to unload afterwards, a kernel panic will occur because the
previous failed iflib driver loead did not properly call "taskqgroup_detach()"
during it's cleanup.

This patch is band-aid for this situation -- don't try allocating MSI or legacy
interrupts if a single MSI-X interrupt was allocated, but fail to load instead.
As well, during the cleanup, properly call taskqgroup_detach() on the admin
task to prevent panics when other iflib drivers unload.

This whole interrupt allocation process actually needs re-doing to properly
support devices with only a single MSI-X interrupt, devices that only support
MSI-X, non-PCI devices, and multiple non-MSIX interrupts, as well.

Signed-off-by: Eric Joyner <erj@freebsd.org>

Reviewed by:	marius@
MFC after:	1 week
Sponsored by:	Intel Corporation
Differential Revision:	https://reviews.freebsd.org/D20747

1 files changed, 7 insertions, 1 deletions

diff --git a/sys/net/iflib.c b/sys/net/iflib.c
index 9b3e7d30363c..f5c7536f0aa7 100644
--- a/sys/net/iflib.c
+++ b/sys/net/iflib.c
@@ -4731,7 +4731,7 @@ iflib_device_register(device_t dev, void *sc, if_shared_ctx_t sctx, if_ctx_t *ct
 			    err);
 			goto fail_queues;
 		}
-	} else {
+	} else if (scctx->isc_intr != IFLIB_INTR_MSIX) {
 		rid = 0;
 		if (scctx->isc_intr == IFLIB_INTR_MSI) {
 			MPASS(msix == 1);
@@ -4741,6 +4741,11 @@ iflib_device_register(device_t dev, void *sc, if_shared_ctx_t sctx, if_ctx_t *ct
 			device_printf(dev, "iflib_legacy_setup failed %d\n", err);
 			goto fail_queues;
 		}
+	} else {
+		device_printf(dev,
+		    "Cannot use iflib with only 1 MSI-X interrupt!\n");
+		err = ENODEV;
+		goto fail_intr_free;
 	}
 
 	ether_ifattach(ctx->ifc_ifp, ctx->ifc_mac.octet);
@@ -4781,6 +4786,7 @@ fail_intr_free:
 fail_queues:
 	iflib_tx_structures_free(ctx);
 	iflib_rx_structures_free(ctx);
+	taskqgroup_detach(qgroup_if_config_tqg, &ctx->ifc_admin_task);
 	IFDI_DETACH(ctx);
 fail_unlock:
 	CTX_UNLOCK(ctx);