linux-kernel - Re: [PATCH 20/22] scsi: hisi_sas: Add v3 code to support ECC and AXI bus fatal error

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Date:   Wed, 17 May 2017 13:38:27 +0100
From:   John Garry <john.garry@...wei.com>
To:     Arnd Bergmann <arnd@...db.de>
CC:     "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        John Garry <john.garry2@...l.dcu.ie>, <linuxarm@...wei.com>,
        <linux-scsi@...r.kernel.org>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        Xiang Chen <chenxiang66@...ilicon.com>
Subject: Re: [PATCH 20/22] scsi: hisi_sas: Add v3 code to support ECC and AXI
 bus fatal error

On 17/05/2017 13:27, Arnd Bergmann wrote:
> On Wed, May 17, 2017 at 12:49 PM, John Garry <john.garry@...wei.com> wrote:
>> > From: Xiang Chen <chenxiang66@...ilicon.com>
>> >
>> > For ECC 1bit error, logic can recover it, so we only print a warning.
>> > For ECC multi-bit and AXI bus fatal error, we panic.
>> >
>> > Signed-off-by: John Garry <john.garry@...wei.com>
>> > Signed-off-by: Xiang Chen <chenxiang66@...ilicon.com>
> This one is tricky as there are conflicting requirements:
>
> - For debugging purposes, you want to continue running the system
>   to figure out what exactly went wrong. Often enough, having the
>   kernel panic means you don't get to see the panic message because
>   console access is unavailable and you cannot log in any more
>
> - For data consistency purposes you want to stop the system as
>   soon as there is any uncorrectable data error
>
> I see that most scsi drivers don't ever call panic or BUG(), though
> you already do so for v1 and v2 hw.
>
> Maybe the SCSI maintainers can provide some more guidance here.
>
>       Arnd
>
> .
>

Hi Arnd,

Actually latest code for v2 has been updated to do a controller reset, 
and not panic, for unrecoverable error:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/scsi/hisi_sas/hisi_sas_v2_hw.c?h=v4.12-rc1#n2926

We never got around to implementing controller reset for v1 as this 
platform (hip05) is not used much anymore.

As for v3, we will change to to do same once controller reset is 
implemented. I should have added this to the commit log.

Thanks,
John