Re: [Qemu-devel] [PATCH] nvme: Set number of queues later in nvme_init()

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 7/10/19 4:57 PM, Michal Privoznik wrote:
> When creating the admin queue in nvme_init() the variable that
> holds the number of queues created is modified before actual
> queue creation. This is a problem because if creating the queue
> fails then the variable is left in inconsistent state. This was
> actually observed when I tried to hotplug a nvme disk. The
> control got to nvme_file_open() which called nvme_init() which
> failed and thus nvme_close() was called which in turn called
> nvme_free_queue_pair() with queue being NULL. This lead to an
> instant crash:
> 
>   #0  0x000055d9507ec211 in nvme_free_queue_pair (bs=0x55d952ddb880, q=0x0) at block/nvme.c:164
>   #1  0x000055d9507ee180 in nvme_close (bs=0x55d952ddb880) at block/nvme.c:729
>   #2  0x000055d9507ee3d5 in nvme_file_open (bs=0x55d952ddb880, options=0x55d952bb1410, flags=147456, errp=0x7ffd8e19e200) at block/nvme.c:781
>   #3  0x000055d9507629f3 in bdrv_open_driver (bs=0x55d952ddb880, drv=0x55d95109c1e0 <bdrv_nvme>, node_name=0x0, options=0x55d952bb1410, open_flags=147456, errp=0x7ffd8e19e310) at block.c:1291
>   #4  0x000055d9507633d6 in bdrv_open_common (bs=0x55d952ddb880, file=0x0, options=0x55d952bb1410, errp=0x7ffd8e19e310) at block.c:1551
>   #5  0x000055d950766881 in bdrv_open_inherit (filename=0x0, reference=0x0, options=0x55d952bb1410, flags=32768, parent=0x55d9538ce420, child_role=0x55d950eaade0 <child_file>, errp=0x7ffd8e19e510) at block.c:3063
>   #6  0x000055d950765ae4 in bdrv_open_child_bs (filename=0x0, options=0x55d9541cdff0, bdref_key=0x55d950af33aa "file", parent=0x55d9538ce420, child_role=0x55d950eaade0 <child_file>, allow_none=true, errp=0x7ffd8e19e510) at block.c:2712
>   #7  0x000055d950766633 in bdrv_open_inherit (filename=0x0, reference=0x0, options=0x55d9541cdff0, flags=0, parent=0x0, child_role=0x0, errp=0x7ffd8e19e908) at block.c:3011
>   #8  0x000055d950766dba in bdrv_open (filename=0x0, reference=0x0, options=0x55d953d00390, flags=0, errp=0x7ffd8e19e908) at block.c:3156
>   #9  0x000055d9507cb635 in blk_new_open (filename=0x0, reference=0x0, options=0x55d953d00390, flags=0, errp=0x7ffd8e19e908) at block/block-backend.c:389
>   #10 0x000055d950465ec5 in blockdev_init (file=0x0, bs_opts=0x55d953d00390, errp=0x7ffd8e19e908) at blockdev.c:602
> 

Fixes: bdd6a90a9e5

> Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> ---
>  block/nvme.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/block/nvme.c b/block/nvme.c
> index 73ed5fa75f..9896b7f7c6 100644
> --- a/block/nvme.c
> +++ b/block/nvme.c
> @@ -613,12 +613,12 @@ static int nvme_init(BlockDriverState *bs, const char *device, int namespace,
>  
>      /* Set up admin queue. */
>      s->queues = g_new(NVMeQueuePair *, 1);
> -    s->nr_queues = 1;
>      s->queues[0] = nvme_create_queue_pair(bs, 0, NVME_QUEUE_SIZE, errp);
>      if (!s->queues[0]) {
>          ret = -EINVAL;
>          goto out;
>      }
> +    s->nr_queues = 1;
>      QEMU_BUILD_BUG_ON(NVME_QUEUE_SIZE & 0xF000);
>      s->regs->aqa = cpu_to_le32((NVME_QUEUE_SIZE << 16) | NVME_QUEUE_SIZE);
>      s->regs->asq = cpu_to_le64(s->queues[0]->sq.iova);
>