linux-kernel - Re: [PATCH] nvme-pci: ignore bogus CRTO according to NVME 2.0 spec

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Date:   Fri, 8 Sep 2023 20:03:08 +0300
From:   Felix Yan <felixonmars@...hlinux.org>
To:     Keith Busch <kbusch@...nel.org>
Cc:     highenthalpyh@...il.com, linux-nvme@...ts.infradead.org,
        linux-kernel@...r.kernel.org, xuwd1@...mail.com
Subject: Re: [PATCH] nvme-pci: ignore bogus CRTO according to NVME 2.0 spec

On 9/8/23 19:51, Keith Busch wrote:
> On Fri, Sep 08, 2023 at 06:54:42PM +0300, Felix Yan wrote:
>> NVME 2.0 spec section 3.1.3 suggests that "Software should not rely on
>> 0h being returned". Here we should safeguard timeout reads when CRTO is 0 and
>> fallback to the old NVME 1.4 compatible field.
> 
> Not sure I follow what you're saying here. We're not really relying on
> CRTO being 0. It was a non-zero capability bit that told the driver to
> use CRTO, and 0 is potentially a valid value a controller could report.

Sorry, I actually meant the opposite: If the whole CRTO field is zeroed, 
we probably shouldn't rely on it as per the spec says.

I understand that 0 could be a valid value, the spec _may_ be a little 
bit unclear here then, if I understand it correctly.

-- 
Regards,
Felix Yan


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