Re: [PATCH] hw/nvme: add new command abort case

[Dmitry Tikhov]

On Wed, Apr 20, 2022 at 12:54:44, Klaus Jensen wrote:
> 
> NVM Command Set Specification v1.0b, Section 5.2.3. It is exactly what
> you quoted above.
> 
> I think you are interpreting
> 
>   "If a command is aborted as a result of the Reference Tag Check bit of
>   the PRCHK field being set to '1', ..."
> 
> as
> 
>    "If a command is aborted *because* the Reference Tag Check bit of the
>    PRCHK field being set to '1', ...".
Yeah, i was interpreting it exactly this way.

> 
> But that is not what it is saying. IMO, the only meaningful
> interpretation is that "If the command is aborted *as a result of* the
> check being done *because* the bit is set, *then* return an error".
Ok, but return error in this context still means to return either
Invalid Protection Information or Invalid Field in Command, isn't it?
Or why would it specify
    ...then that command should be aborted with a status code of Invalid
        Protection Information, but may be aborted with a status code of
        Invalid Field in Command
exactly this 2 status codes?

> 
> Your interpretation would break existing hosts that set the bit.

I also opened NVM Express 1.4 "8.3.1.5 Control of Protection Information
Checking - PRCHK" and it says
    For Type 3 protection, if bit 0 of the PRCHK field is set to ‘1’, then
        the command should be aborted with status Invalid Protection
        Information, but may be aborted with status Invalid Field in Command.
        The controller may ignore the ILBRT and EILBRT fields when Type 3
        protection is used because the computed reference tag remains
        unchanged.
I think it marks clear intent to abort cmd with "Invalid Protection
Information" or "Invalid Field in Command" status codes exactly in case
reftag check bit is set. Also isn't "may ignore the ILBRT and EILBRT 
fields" means not to compare reftag with ILBRT/EILBRT? If it is not 
compared then reftag check error can't be returned.

But anyways, spec says that "should" and "may" indicates flexibility of
choice and not mandatory behavior. So if you think that current behavior
is right i don't insist.