[SeaBIOS] [PATCH v2] nvme: Use the Maximum Queue Entries Supported (MQES) to initialize I/O queues

[Sironi, Filippo]

> On 14. Oct 2017, at 17:15, Kevin O'Connor <kevin at koconnor.net> wrote:
> 
> On Thu, Oct 12, 2017 at 12:42:34AM +0200, Filippo Sironi wrote:
>> Use the Maximum Queue Entries Supported (MQES) to initialize I/O queues
>> depth rather than picking a fixed number (256) which might not be
>> supported by some NVMe controllers (the NVMe specification says that an
>> NVMe controller may support any number between 2 to 4096).
>> 
>> Still cap the I/O queues depth to 256 since, during my testing, SeaBIOS
>> was running out of memory when using something higher than 256 (4096 on
>> the NVMe controller that I've had a chance to try).
> 
> Okay, thanks.  So, it sounds like it is a bug fix (as it could prevent
> a failure if the hardware queue depth is less than 256).
> 
> I'd prefer not to introduce min()/max() macros to individual driver
> files.  (I'm fine with a patch that globally introduces min/max, but I
> don't think we should be adding them piecemeal.)  Are you okay with
> the patch below instead?
> 
> -Kevin

Looks good to me.

Thanks,
Filippo


> Author: Filippo Sironi <sironi at amazon.de>
> Date:   Thu Oct 12 00:42:34 2017 +0200
> 
>    nvme: Use the Maximum Queue Entries Supported (MQES) to initialize I/O queues
> 
>    Use the Maximum Queue Entries Supported (MQES) to initialize I/O queues
>    depth rather than picking a fixed number (256) which might not be
>    supported by some NVMe controllers (the NVMe specification says that an
>    NVMe controller may support any number between 2 to 4096).
> 
>    Still cap the I/O queues depth to 256 since, during my testing, SeaBIOS
>    was running out of memory when using something higher than 256 (4096 on
>    the NVMe controller that I've had a chance to try).
> 
>    Signed-off-by: Filippo Sironi <sironi at amazon.de>
> 
> diff --git a/src/hw/nvme.c b/src/hw/nvme.c
> index 946487f..e6d739d 100644
> --- a/src/hw/nvme.c
> +++ b/src/hw/nvme.c
> @@ -318,8 +318,11 @@ nvme_create_io_cq(struct nvme_ctrl *ctrl, struct nvme_cq *cq, u16 q_idx)
> {
>     int rc;
>     struct nvme_sqe *cmd_create_cq;
> +    u16 length = 1 + (ctrl->reg->cap & 0xffff);
> +    if (length > NVME_PAGE_SIZE / sizeof(struct nvme_cqe))
> +        length = NVME_PAGE_SIZE / sizeof(struct nvme_cqe);
> 
> -    rc = nvme_init_cq(ctrl, cq, q_idx, NVME_PAGE_SIZE / sizeof(struct nvme_cqe));
> +    rc = nvme_init_cq(ctrl, cq, q_idx, length);
>     if (rc) {
>         goto err;
>     }
> @@ -359,8 +362,11 @@ nvme_create_io_sq(struct nvme_ctrl *ctrl, struct nvme_sq *sq, u16 q_idx, struct
> {
>     int rc;
>     struct nvme_sqe *cmd_create_sq;
> +    u16 length = 1 + (ctrl->reg->cap & 0xffff);
> +    if (length > NVME_PAGE_SIZE / sizeof(struct nvme_cqe))
> +        length = NVME_PAGE_SIZE / sizeof(struct nvme_cqe);
> 
> -    rc = nvme_init_sq(ctrl, sq, q_idx, NVME_PAGE_SIZE / sizeof(struct nvme_cqe), cq);
> +    rc = nvme_init_sq(ctrl, sq, q_idx, length, cq);
>     if (rc) {
>         goto err;
>     }
> 

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