Re: [PATCH v5 07/18] nvme: add max_ioqpairs device parameter

[Klaus Jensen]

On May  5 07:48, Klaus Jensen wrote:
> From: Klaus Jensen <address@hidden>
> 
> The num_queues device paramater has a slightly confusing meaning because
> it accounts for the admin queue pair which is not really optional.
> Secondly, it is really a maximum value of queues allowed.
> 
> Add a new max_ioqpairs parameter that only accounts for I/O queue pairs,
> but keep num_queues for compatibility.
> 
> Signed-off-by: Klaus Jensen <address@hidden>
> Reviewed-by: Maxim Levitsky <address@hidden>
> Reviewed-by: Philippe Mathieu-Daudé <address@hidden>
> Reviewed-by: Keith Busch <address@hidden>
> ---
>  hw/block/nvme.c | 51 ++++++++++++++++++++++++++++++-------------------
>  hw/block/nvme.h |  3 ++-
>  2 files changed, 33 insertions(+), 21 deletions(-)
> 
> diff --git a/hw/block/nvme.c b/hw/block/nvme.c
> index 623a88be93dc..3875a5f3dcbf 100644
> --- a/hw/block/nvme.c
> +++ b/hw/block/nvme.c
> @@ -1571,7 +1581,8 @@ static Property nvme_props[] = {
>                       HostMemoryBackend *),
>      DEFINE_PROP_STRING("serial", NvmeCtrl, params.serial),
>      DEFINE_PROP_UINT32("cmb_size_mb", NvmeCtrl, params.cmb_size_mb, 0),
> -    DEFINE_PROP_UINT32("num_queues", NvmeCtrl, params.num_queues, 64),
> +    DEFINE_PROP_UINT32("num_queues", NvmeCtrl, params.num_queues, 0),
> +    DEFINE_PROP_UINT32("max_ioqpairs", NvmeCtrl, params.max_ioqpairs, 64),
>      DEFINE_PROP_END_OF_LIST(),
>  };
>  

I noticed that this default of 64 makes the default configuration
unsafe by allowing the cq->cqid < 64 assert in nvme_irq_{,de}assert() to
trigger if the pin-based interrupt logic is used (under SPDK for
instance). The assert protects against undefined behavior caused by
shifting by more than 63 into the 64 bit irq_status variable.

As far as I can tell, the assert, the shift and the size of the
irq_status variable is bogus, so I posted a patch for this in
"hw/block/nvme: fixes for interrupt behavior". Preferably that should go
in before this series.