linux-kernel - Re: [PATCH v5 01/10] hyperv: Convert Hyper-V status codes to strings

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Message-ID: <70b62e52-639a-4026-9a52-102d1de46ffd@linux.microsoft.com>
Date: Thu, 27 Feb 2025 15:25:17 -0800
From: Easwar Hariharan <eahariha@...ux.microsoft.com>
To: Roman Kisel <romank@...ux.microsoft.com>
Cc: eahariha@...ux.microsoft.com,
 Nuno Das Neves <nunodasneves@...ux.microsoft.com>,
 linux-hyperv@...r.kernel.org, x86@...nel.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-arch@...r.kernel.org, linux-acpi@...r.kernel.org, kys@...rosoft.com,
 haiyangz@...rosoft.com, wei.liu@...nel.org, mhklinux@...look.com,
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Subject: Re: [PATCH v5 01/10] hyperv: Convert Hyper-V status codes to strings

On 2/27/2025 3:08 PM, Roman Kisel wrote:
> 
> 
> On 2/27/2025 2:54 PM, Easwar Hariharan wrote:
> [...]
> 
>>
>> Sorry, I have to disagree with this, a recent commit of mine[1] closed a WSL
>> issue that was open for over 2 years for, partly, the utter uselessness of
>> the hex return code of the hypercall.
> 
> Thanks for your efforts, and sorry to hear you had a frustrating
> debugging experience (sounds like it).

TBF, I didn't personally struggle with it for 2 years, IMHO, it was the opaqueness
of what the value meant that contributed to user pain.

> 
> Would be great to learn the details to understand how this function is
> going to improve the situation:
> 
> 1. How come the hex error code was useless, what is not matching
>    anything in the Linux headers?

It doesn't match anything in the Linux headers, but it's an NTSTATUS, not HVSTATUS.

Coming from the PoV of a user, it would be a much more useful message to see:

[  249.512760] hv_storvsc fd1d2cbd-ce7c-535c-966b-eb5f811c95f0: tag#683 cmd 0x28 status: scsi 0x2 srb 0x4 hv STATUS_UNSUCCESSFUL

than 

[  249.512760] hv_storvsc fd1d2cbd-ce7c-535c-966b-eb5f811c95f0: tag#683 cmd 0x28 status: scsi 0x2 srb 0x4 hv 0xc0000001

> 2. How having "Unknown" in the log can possibly be better?

IMHO, seeing "Unknown" in an error report means that there's a new return value
that needs to be mapped to errno in hv_status_to_errno() and updated here as well.

> 3. Given that the select hv status codes and the proposed strings have
>    1:1 correspondence, and there is the 1:N catch-all case for the
>    "Unknown", how's that better?
> 

I didn't really follow this question, but I suppose the answer to Q2 answers this as
well. If not, please expand and I'll try to answer.

Thanks,
Easwar (he/him)