Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Content-Type: text/plain;
        charset=us-ascii
Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.120.23.2.1\))
Subject: Re: [PATCH v2] nvme/pci: Add new quirk for SK hynix PC400 NLB
 off-by-one bug
From:   Kai-Heng Feng <kai.heng.feng@canonical.com>
In-Reply-To: <20200723160325.GA17996@lst.de>
Date:   Fri, 24 Jul 2020 00:10:39 +0800
Cc:     kbusch@kernel.org, axboe@fb.com, 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>
Content-Transfer-Encoding: 8BIT
Message-Id: <45DFD291-E6BF-48DE-A447-6FA4086D40A5@canonical.com>
References: <20200417083641.28205-1-kai.heng.feng@canonical.com>
 <20200723155731.22313-1-kai.heng.feng@canonical.com>
 <20200723160325.GA17996@lst.de>
To:     Christoph Hellwig <hch@lst.de>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


> On Jul 24, 2020, at 00:03, Christoph Hellwig <hch@lst.de> wrote:
> 
> 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.

Ok, will send a new version based on your suggestion.

> 
>> 
>> 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..

Well, because it took some time for the vendor to find the root cause...
Here's the v1:
https://lkml.org/lkml/2020/4/17/169

Kai-Heng