On Tue, 26 Jan 2021, Jan Beulich wrote: > On 26.01.2021 12:17, Bertrand Marquis wrote: > > > > > >> On 26 Jan 2021, at 11:11, Jan Beulich <jbeul...@suse.com> wrote: > >> > >> On 26.01.2021 12:06, Bertrand Marquis wrote: > >>>> On 26 Jan 2021, at 09:22, Jan Beulich <jbeul...@suse.com> wrote: > >>>> On 25.01.2021 22:27, Stefano Stabellini wrote: > >>>>> @@ -77,7 +77,7 @@ config SBSA_VUART_CONSOLE > >>>>> SBSA Generic UART implements a subset of ARM PL011 UART. > >>>>> > >>>>> config ARM_SSBD > >>>>> - bool "Speculative Store Bypass Disable" if EXPERT > >>>>> + bool "Speculative Store Bypass Disable (UNSUPPORTED)" if > >>>>> UNSUPPORTED > >>>>> depends on HAS_ALTERNATIVE > >>>>> default y > >>>>> help > >>>>> @@ -87,7 +87,7 @@ config ARM_SSBD > >>>>> If unsure, say Y. > >>>>> > >>>>> config HARDEN_BRANCH_PREDICTOR > >>>>> - bool "Harden the branch predictor against aliasing attacks" if > >>>>> EXPERT > >>>>> + bool "Harden the branch predictor against aliasing attacks > >>>>> (UNSUPPORTED)" if UNSUPPORTED > >>>>> default y > >>>>> help > >>>>> Speculation attacks against some high-performance processors > >>>>> rely on > >>>> > >>>> Both of these default to y and have their _prompt_ > >>>> conditional upon EXPERT. Which means only an expert can turn them > >>>> _off_. Which doesn't make it look like these are unsupported? Or > >>>> if anything, turning them off is unsupported? > >>> > >>> ...You could see that as EXPERT/UNSUPPORTED options can only be > >>> “modified” from their default value if EXPERT/UNSUPPORTED is activated. > >> > >> But this is nothing you can recognize when configuring Xen > >> (i.e. seeing just these prompts). > > > > Maybe something we could explain more clearly in the UNSUPPORTED/EXPERT > > config parameters instead ? > > We could also make that more clear in the help of such parameters directly. > > > > I do not see how we could make that more clear directly in the prompt (as > > making it too long is not a good solution). > > My main request is that such tags be added only if there's > absolutely no ambiguity. Anything else (requiring longer > explanations in many cases) should be expressed in the help > text of the option, or in yet other ways (a referral to > SUPPORT.md comes to mind).
I actually agree completely with you. In the case of ARM_SSBD and HARDEN_BRANCH_PREDICTOR, they should remain as they are today I think.
