linux-kernel - Re: [PATCH 2/3] scsi: pm80xx: Do not issue hard reset before NCQ EH

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ZmgNkK8haUisJ5-b@ryzen.lan>
Date: Tue, 11 Jun 2024 10:40:48 +0200
From: Niklas Cassel <cassel@...nel.org>
To: TJ Adams <tadamsjr@...gle.com>
Cc: Jack Wang <jinpu.wang@...ud.ionos.com>,
	"James E . J . Bottomley" <James.Bottomley@...senpartnership.com>,
	"Martin K . Petersen" <martin.petersen@...cle.com>,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	Igor Pylypiv <ipylypiv@...gle.com>
Subject: Re: [PATCH 2/3] scsi: pm80xx: Do not issue hard reset before NCQ EH

Hello Igor, TJ,

On Fri, Jun 07, 2024 at 05:57:42PM +0000, TJ Adams wrote:
> From: Igor Pylypiv <ipylypiv@...gle.com>
> 
> v6.2 commit 811be570a9a8 ("scsi: pm8001: Use sas_ata_device_link_abort()

Do not specify kernel version (it is irrelevant), SHA1 is enough.

> to handle NCQ errors") removed duplicate NCQ EH from the pm80xx driver
> and started relying on libata to handle the NCQ errors. The PM8006
> controller has a special EH sequence that was added in v4.15 commit
> 869ddbdcae3b ("scsi: pm80xx: corrected SATA abort handling sequence.").

Do not specify kernel version (it is irrelevant), SHA1 is enough.

Since the code added in 869ddbdcae3b still exists in the pm80xx driver,
I think that you should mention the commits in chronological order.
(Right now you mention the oldest still existing code last, which seems
a bit backwards.)

> The special EH sequence issues a hard reset to a drive before libata EH
> has a chance to read the NCQ log page. Libata EH gets confused by empty
> NCQ log page which results in HSM violation. The failed command gets
> retried a few times and each time fails with the same HSM violation.
> Finally, libata decides to disable NCQ due to subsequent HSM vioaltions.

s/vioaltions/violations/

I'm not an expert in libsas EH, but I think that your commit message fails
to explain why this change actually fixes anything. You do not mention the
relationship between the code that you add pm8001_work_fn() and the
existing code in pm8001_abort_task(), and the order in which the functions
get executed.

Does calling sas_execute_internal_abort_dev() from pm8001_work_fn() ensure
that the libsas EH is never invoked? Or does it cancel the hard reset that
is part of the "special EH sequence" in pm8001_abort_task() ?

Wouldn't it be better if this was fixed in pm8001_abort_task() or similar
instead? It appears that the code you add to pm8001_work_fn() (that has a
very ugly if (pm8006)) is only there to undo or avoid the hard reset that
is done in pm8001_abort_task() (which also has a very ugly if (pm8006)).

Now we have this ugly if (pm8006) in two different functions... which
makes my "this could be solved in a nicer way" detector go off.

If this patch (as is) is really the way to go, then I think there should
be a more detailed reasoning why this change is the most sensible one.

Kind regards,
Niklas