linux-kernel - Re: [PATCH] nvme: clear the prp2 field of the nvme command.

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Message-ID: <15de4902-03e7-0d2c-4b4c-45d713d0f1fd@nvidia.com>
Date:   Tue, 29 Nov 2022 04:16:59 +0000
From:   Chaitanya Kulkarni <chaitanyak@...dia.com>
To:     Lei Rao <lei.rao@...el.com>,
        "kbusch@...nel.org" <kbusch@...nel.org>,
        "axboe@...com" <axboe@...com>, "hch@....de" <hch@....de>,
        "sagi@...mberg.me" <sagi@...mberg.me>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nvme: clear the prp2 field of the nvme command.

On 11/28/22 17:47, Lei Rao wrote:
> If the prp2 field is not filled in nvme_setup_prp_simple(), the prp2
> field is garbage data. According to nvme spec, the prp2 is reserved if
> the data transfer does not cross a memory page boundary. Writing a
> reserved coded value into a controller property field produces undefined
> results, so it needs to be cleared in nvme_setup_rw().
> 
> Signed-off-by: Lei Rao <lei.rao@...el.com>

if it is reserved then controller shoule ignore this field, no ?

not sure if original author wanted to avoid an extra assignment
in the fast path with assumption that reserved fields should be
ignored if it is then we should avoid this, if not then looks good

Reviewed-by: Chaitanya Kulkarni <kch@...dia.com>

-ck