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Date:   Thu, 23 Jul 2020 18:03:25 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Kai-Heng Feng <kai.heng.feng@canonical.com>
Cc:     kbusch@kernel.org, axboe@fb.com, hch@lst.de, sagi@grimberg.me,
        kyounghwan sohn <kyounghwan.sohn@sk.com>,
        "open list:NVM EXPRESS DRIVER" <linux-nvme@lists.infradead.org>,
        open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] nvme/pci: Add new quirk for SK hynix PC400 NLB
 off-by-one bug
Message-ID: <20200723160325.GA17996@lst.de>
References: <20200417083641.28205-1-kai.heng.feng@canonical.com> <20200723155731.22313-1-kai.heng.feng@canonical.com>
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On Thu, Jul 23, 2020 at 11:57:31PM +0800, Kai-Heng Feng wrote:
> After commit 6e02318eaea5 ("nvme: add support for the Write Zeroes
> command"), SK hynix PC400 becomes very slow with the following error
> message:
> [  224.567695] blk_update_request: operation not supported error, dev nvme1n1, sector 499384320 op 0x9:(WRITE_ZEROES) flags 0x1000000 phys_seg 0 prio class 0]
> 
> SK Hynix PC400 has a buggy firmware that treats NLB as max value instead
> of a range, so the NLB passed isn't a valid value to the firmware.
> 
> According to SK hynix there are three commands are affected:
> - Write Zeroes
> - Compare
> - Write Uncorrectable
> 
> Write Uncorrectable isn't implemented yet, so add a new quirk to
> workaround the former two commands.

compare isn't implemented either in the kernel, and we certainly
aren't going to do these quirks for passthrough.  So I think we really
want a "write zeroes is buggy" quirk and just disable issuing that
command from the driver.

> 
> BugLink: https://bugs.launchpad.net/bugs/1872383
> Cc: kyounghwan sohn <kyounghwan.sohn@sk.com>
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
> ---
> v2:
> - SK hynix found the root cause so change the approach accordingly.
> - lspci is wrong, the device is PC400 instead of SC300.

I don't remember seing a v1..