Re: [BUG] nvme driver crash

[Omar Sandoval <osandov@osandov.com>]

On Wed, Jul 26, 2017 at 10:34:43AM -0700, Christoph Hellwig wrote:
> On Tue, Jul 25, 2017 at 03:24:08PM -0700, Shaohua Li wrote:
> > Disable CONIFG_SMP, kernel crashes at boot time, here is the log.
> 
> I can reproduce the issue.  Unfortunately the addresss in the bug
> doesn't make any sense to me when resolving it using gdb, as t just
> points to the line where blk_mq_init_queue calls
> blk_alloc_queue_node.
> 
> Can you check if you get better results in your build?

It's crashing on that line because ctrl->tagset is NULL, which is
because...

irq_create_affinity_masks() returns NULL on !CONFIG_SMP
-> pci_irq_get_affinity() returns NULL
-> blk_mq_pci_map_queues() returns -EINVAL
-> blk_mq_alloc_tag_set() returns -EINVAL
-> nvme_dev_add() doesn't set ctrl->tagset

The two-fold fix would be to make the nvme driver handle
blk_mq_alloc_tag_set() failing and to fall back to a dumb mapping in
blk_mq_pci_map_queues(), but I don't know what the best way to do those
is.