linux-kernel - Re: [PATCH] arm64: Kconfig.platforms: fix warning unmet direct dependencies

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Date:   Wed, 30 Jan 2019 18:21:48 +0000
From:   Will Deacon <will.deacon@....com>
To:     Anders Roxell <anders.roxell@...aro.org>
Cc:     Lucas Stach <l.stach@...gutronix.de>,
        Catalin Marinas <catalin.marinas@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: Kconfig.platforms: fix warning unmet direct
 dependencies

On Wed, Jan 30, 2019 at 09:43:21AM +0100, Anders Roxell wrote:
> On 2019-01-25 16:57, Lucas Stach wrote:
> > Am Freitag, den 25.01.2019, 14:32 +0000 schrieb Catalin Marinas:
> > > On Tue, Jan 15, 2019 at 08:18:39PM +0100, Anders Roxell wrote:
> > > > When ARCH_MXC get enabled, ARM64_ERRATUM_845719 will be selected and
> > > > this warning will happen when COMPAT isn't set.
> > > > 
> > > > WARNING: unmet direct dependencies detected for ARM64_ERRATUM_845719
> > > >   Depends on [n]: COMPAT [=n]
> > > >   Selected by [y]:
> > > >   - ARCH_MXC [=y]
> > > > 
> > > > Rework to add 'if COMPAT' before ARM64_ERRATUM_845719 gets selected,
> > > > since ARM64_ERRATUM_845719 depends on COMPAT.
> > > > 
> > > > > > Signed-off-by: Anders Roxell <anders.roxell@...aro.org>
> > > > ---
> > > >  arch/arm64/Kconfig.platforms | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > 
> > > > diff --git a/arch/arm64/Kconfig.platforms b/arch/arm64/Kconfig.platforms
> > > > index 251ecf34cb02..d4faca775d9c 100644
> > > > --- a/arch/arm64/Kconfig.platforms
> > > > +++ b/arch/arm64/Kconfig.platforms
> > > > @@ -145,7 +145,7 @@ config ARCH_MVEBU
> > > >  config ARCH_MXC
> > > > > >  	bool "ARMv8 based NXP i.MX SoC family"
> > > > > >  	select ARM64_ERRATUM_843419
> > > > > > -	select ARM64_ERRATUM_845719
> > > > > > +	select ARM64_ERRATUM_845719 if COMPAT
> > > > > >  	help
> > > > > >  	  This enables support for the ARMv8 based SoCs in the
> > > >  	  NXP i.MX family.
> > > 
> > > Actually, do we need to select the errata workarounds explicitly? That
> > > seems to be the only case where we do it (commit 930507c18304, "arm64:
> > > add basic Kconfig symbols for i.MX8"). They are default y, so we
> > > shouldn't need to force them on.
> > 
> > This is based on past experience. We've had a lot of cases were people
> > did not enable the necessary CPU errata workaround, which then usually
> > lead to very hard to debug system failures. It is on our list of things
> > to look out for now, but I would feel much better if there is just no
> > chance for a user to misconfigure the kernel in this way.
> > 
> 
> Would a better approach be to remove the 'depends on COMPAT' in the
> Kconfig and move it into the src files instead see below.

I'd prefer to keep the dependency here, because the erratum is not
applicable for native (64-bit) userspace.

I think your original patch is fine, so:

Acked-by: Will Deacon <will.deacon@....com>

Will