linux-kernel - Re: [PATCH v16 6/9] nvmet-passthru: Add passthru code to process commands

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Message-ID: <20200724193351.GA2857771@dhcp-10-100-145-180.wdl.wdc.com>
Date:   Fri, 24 Jul 2020 12:33:51 -0700
From:   Keith Busch <kbusch@...nel.org>
To:     Logan Gunthorpe <logang@...tatee.com>
Cc:     linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>, Jens Axboe <axboe@...com>,
        Chaitanya Kulkarni <Chaitanya.Kulkarni@....com>,
        Max Gurtovoy <maxg@...lanox.com>,
        Stephen Bates <sbates@...thlin.com>
Subject: Re: [PATCH v16 6/9] nvmet-passthru: Add passthru code to process
 commands

On Fri, Jul 24, 2020 at 11:25:17AM -0600, Logan Gunthorpe wrote:
> +	/*
> +	 * The passthru NVMe driver may have a limit on the number of segments
> +	 * which depends on the host's memory fragementation. To solve this,
> +	 * ensure mdts is limitted to the pages equal to the number of

                          limited

> +	/* don't support fuse commands */
> +	id->fuses = 0;

If a host were to set a fuse, the target should return an Invalid Field
error. Just to future-proof, rejecting commands with any flags set
(other than SGL, which you handled in patch 1/9) is probably what should
happen, like:

> +u16 nvmet_parse_passthru_io_cmd(struct nvmet_req *req)
> +{

	if (req->cmd->common.flags & ~NVME_CMD_SGL_ALL)
		return NVME_SC_INVALID_FIELD;

Or maybe we could obviate the need for 1/9 with something like:

	req->cmd->common.flags &= ~NVME_CMD_SGL_ALL;
	if (req->cmd->common.flags)
		return NVME_SC_INVALID_FIELD;