Re: [dpdk-dev] [EXT] Re: [PATCH] config/arm: add ability to express arch extensions

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

<snip>

> >>
> >> >
> >> > The patch still holds true for CRC though as it is listed
> >> > separately below
> >> > https://urldefense.proofpoint.com/v2/url?u=https-
> >3A__developer.arm.com_architectures_cpu-2Darchitecture_a-
> >2D&d=DwIFAg&c=nKjWec2b6R0mOyPaz7xtfQ&r=E3SgYMjtKCMVsB-
> >fmvgGV3o-
> >g_fjLhk5Pupi9ijohpc&m=i3kC8htMiHjXMoJWUn6QlDVZQCblbFrIJyMcW
> >d9nAmM&s=fA4SM6O3iC2HXIK1qSbOHzxVeHoYqcfUebEOwioHC7c&e=
> >> > profile/exploration-tools/feature-names-for-a-profile
> >CRC is mandatory starting in V8.1, refer to Arm-ARM document.
> >
> >> >
> >> > Also, looks like sve2 support in n2 core might be optional as per
> >above doc?
> >> I need to check on this. Some of the info here might not be public yet.
> >I found [1]. SVE2 is mandatory feature.
> >
> 
> I see thanks for the info I will remove extension from cnxk.
> 
> Do you think the extension infra is still useful for other cases? i.e. older cores
> or cases where vendor wants to enable some extensions by default?
> 
> I found a document[1] which describes about extensions not enabled by
> default but supported by a given march.
> In case of n2 I think memory tagging is one such feature
I think the reference is providing a different information than what you are trying to achieve here.

It looks like you are trying to address a use case where in the same CPU IP has different features enabled/disabled on different SoCs.
This is a valid use case from crypto perspective (due to export control reasons) where-in 2 different SoCs might have crypto enabled/disabled. I am not sure if other features can be enabled/disabled. But, Crypto feature is a good enough reason to address such a use case.

IMO,  we should capture the SoC specific details in SoC specific files, in this case in 'arm64_cn10k_linux_gcc'. I believe there were some challenges in doing this.
Juraj, do you remember the exact issue?

> 
> [1]https://developer.arm.com/tools-and-software/open-source-
> software/developer-tools/gnu-toolchain/architecture-support
> 
> 
> >[1] https://urldefense.proofpoint.com/v2/url?u=https-
> >3A__developer.arm.com_ip-
> >2Dproducts_processors_neoverse_neoverse-
> >2Dn2&d=DwIFAg&c=nKjWec2b6R0mOyPaz7xtfQ&r=E3SgYMjtKCMVsB-
> >fmvgGV3o-
> >g_fjLhk5Pupi9ijohpc&m=i3kC8htMiHjXMoJWUn6QlDVZQCblbFrIJyMcW
> >d9nAmM&s=kP_X-Co0cl4pZ64BZqy5rAFUlkMZE-3EhTVBabm3SW8&e=
> >
> ><snip>