Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Tue, 10 May 2022 11:20:40 +0200 | Subject | Re: [PATCH] arm64: ARM Scalable Matrix Extension is ARMv9-A |
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Hi Will,
On Tue, May 10, 2022 at 11:15 AM Will Deacon <will@kernel.org> wrote: > On Mon, May 09, 2022 at 03:40:30PM +0200, Geert Uytterhoeven wrote: > > The help text for the config option to enable support for the ARM > > Scalable Matrix Extension does not mention the specification baseline > > for this extension. Make it clear this is an extension for the ARMv9-A > > architecture, so users know when it is safe to disable this option, > > which is enabled by default. > > > > Fixes: a1f4ccd25cc25625 ("arm64/sme: Provide Kconfig for SME") > > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> > --- a/arch/arm64/Kconfig > > +++ b/arch/arm64/Kconfig > > @@ -1964,9 +1964,9 @@ config ARM64_SME > > default y > > depends on ARM64_SVE > > help > > - The Scalable Matrix Extension (SME) is an extension to the AArch64 > > - execution state which utilises a substantial subset of the SVE > > - instruction set, together with the addition of new architectural > > + The Scalable Matrix Extension (SME) is an ARMv9-A extension to the > > + AArch64 execution state which utilises a substantial subset of the > > + SVE instruction set, together with the addition of new architectural > > Why is this useful information? The v9 vs v8 distinction is purely a
Because I tend to disable support for extensions that are not present in Renesas SoCs in the (local) renesas_defconfig. If it's ARMv9, I know it's not present in e.g. Cortex-A57 or A-76.
> marketing thing, so I'd be _very_ wary of drawing any technical conclusions > based on that, especially as Arm have a track record for "backporting" > features into older CPUs if there is demand for it. Do you know what the > toolchains have done here? (i.e. is there march=armv9-a or can you do > march=armv8-a+sme or something else?).
I have no idea. This option doesn't seem to control any compiler flags?
> Having said all that, we do already have the Kconfig menu entries for "Armv8.x > architectural features", so adding one for "Armv9" would be consistent with > that if you really want it.
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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