netdev - RE: [PATCH v2 3/6] ethtool: introduce new ioctl for per-queue settings

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Date:   Thu, 7 Feb 2019 23:43:53 +0000
From:   "Nunley, Nicholas D" <nicholas.d.nunley@...el.com>
To:     Michal Kubecek <mkubecek@...e.cz>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
        "linville@...driver.com" <linville@...driver.com>,
        "nhorman@...hat.com" <nhorman@...hat.com>,
        "sassmann@...hat.com" <sassmann@...hat.com>
Subject: RE: [PATCH v2 3/6] ethtool: introduce new ioctl for per-queue
 settings

> -----Original Message-----
> From: Michal Kubecek [mailto:mkubecek@...e.cz]
> Sent: Wednesday, February 6, 2019 4:43 AM
> To: netdev@...r.kernel.org
> Cc: Kirsher, Jeffrey T <jeffrey.t.kirsher@...el.com>; linville@...driver.com;
> Nunley, Nicholas D <nicholas.d.nunley@...el.com>; nhorman@...hat.com;
> sassmann@...hat.com
> Subject: Re: [PATCH v2 3/6] ethtool: introduce new ioctl for per-queue
> settings
> 
> On Tue, Feb 05, 2019 at 04:01:03PM -0800, Jeff Kirsher wrote:
> > +static int do_perqueue(struct cmd_context *ctx) {
> > +	__u32
> queue_mask[__KERNEL_DIV_ROUND_UP(MAX_NUM_QUEUE, 32)] = {0};
> > +	int i, n_queues = 0;
> > +
> > +	if (ctx->argc == 0)
> > +		exit_bad_args();
> > +
> > +	/*
> > +	 * The sub commands will be applied to
> > +	 * all queues if no queue_mask set
> > +	 */
> > +	if (strncmp(*ctx->argp, "queue_mask", 10)) {
> 
> This would match any string starting with "queue_mask", is it intended?

No, I'll fix this. I don't know that there are any use cases where this distinction would matter, but then again there's no reason to have it match this way.

> 
> > +		n_queues = find_max_num_queues(ctx);
> > +		if (n_queues < 0) {
> > +			perror("Cannot get number of queues");
> > +			return -EFAULT;
> > +		}
> > +		for (i = 0; i < n_queues / 32; i++)
> > +			queue_mask[i] = ~0;
> > +		queue_mask[i] = (1 << (n_queues - i * 32)) - 1;
> 
> It's unlikely today, I guess, but in theory, this would overflow if n_queues ==
> MAX_NUM_QUEUE

Nice catch, I'll add a check to avoid this.

> > +		fprintf(stdout,
> > +			"The sub commands will be applied to all %d
> queues\n",
> > +			n_queues);
> > +	} else {
> > +		ctx->argc--;
> > +		ctx->argp++;
> > +		n_queues = set_queue_mask(queue_mask, *ctx->argp);
> > +		if (n_queues < 0) {
> > +			perror("Invalid queue mask");
> > +			return n_queues;
> > +		}
> > +		ctx->argc--;
> > +		ctx->argp++;
> > +	}
> > +
> > +	i = find_option(ctx->argc, ctx->argp);
> > +	if (i < 0)
> > +		exit_bad_args();
> > +
> > +	/* no sub_command support yet */
> > +
> > +	return 0;
> > +}
> 
> Michal Kubecek