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Re: [PATCH 17/17] hw/block/nvme: change controller pci id

From: Philippe Mathieu-Daudé
Subject: Re: [PATCH 17/17] hw/block/nvme: change controller pci id
Date: Mon, 7 Sep 2020 10:36:58 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0

On 9/7/20 9:23 AM, Klaus Jensen wrote:
> On Sep  7 04:28, Philippe Mathieu-Daudé wrote:
>> +David in case
>> On 9/4/20 4:19 PM, Klaus Jensen wrote:
>>> From: Klaus Jensen <k.jensen@samsung.com>
>>> There are two reasons for changing this:
>>>   1. The nvme device currently uses an internal Intel device id.
>>>   2. Since commits "nvme: fix write zeroes offset and count" and "nvme:
>>>      support multiple namespaces" the controller device no longer has
>>>      the quirks that the Linux kernel think it has.
>>>      As the quirks are applied based on pci vendor and device id, change
>>>      them to get rid of the quirks.
>>> To keep backward compatibility, add a new 'x-use-intel-id' parameter to
>>> the nvme device to force use of the Intel vendor and device id. This is
>>> off by default but add a compat property to set this for 5.1 machines
>>> and older.
>> So now what happens if you start a 5.1 machine with a recent kernel?
>> Simply the kernel will use unnecessary quirks, or are there more
>> changes in behavior?
> Yes, the kernel will then just apply unneccesary quirks, these are:
>   1. NVME_QUIRK_IDENTIFY_CNS which says that the device does not support
>      anything else than values 0x0 and 0x1 for CNS (Identify Namespace and
>      Identify Namespace). With multiple namespace support, this just
>      means that the kernel will "scan" namespaces instead of using
>      "Active Namespace ID list" (CNS 0x2).
>   2. NVME_QUIRK_DISABLE_WRITE_ZEROES. The nvme device started out with a
>      broken Write Zeroes implementation which has since been fixed in
>      commit 9d6459d21a6e ("nvme: fix write zeroes offset and count").

OK thanks. Can you amend that information in the commit
description please?



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