linux-kernel - Re: [PATCH] arm64: Disallow combination of ARCH

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Date:	Thu, 28 Jan 2016 11:08:20 +0000
From:	Will Deacon <will.deacon@....com>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	dann frazier <dann.frazier@...onical.com>,
	Duc Dang <dhdang@....com>, Kumar Sankaran <ksankaran@....com>,
	Loc Ho <lho@....com>, Feng Kan <fkan@....com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] arm64: Disallow combination of ARCH_XGENE and 16K page
 size

On Thu, Jan 28, 2016 at 10:34:41AM +0000, Catalin Marinas wrote:
> On Wed, Jan 27, 2016 at 04:10:30PM -0700, dann frazier wrote:
> > 16K page size is an optional feature of the architecture, and is not
> > supported by the X-Gene SoC family.
> > 
> > Signed-off-by: dann frazier <dann.frazier@...onical.com>
> > ---
> >  arch/arm64/Kconfig.platforms | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/arch/arm64/Kconfig.platforms b/arch/arm64/Kconfig.platforms
> > index 21074f6..b241290 100644
> > --- a/arch/arm64/Kconfig.platforms
> > +++ b/arch/arm64/Kconfig.platforms
> > @@ -133,6 +133,7 @@ config ARCH_VEXPRESS
> >  
> >  config ARCH_XGENE
> >  	bool "AppliedMicro X-Gene SOC Family"
> > +	depends on !ARM64_16K_PAGES
> >  	help
> >  	  This enables support for AppliedMicro X-Gene SOC Family
> 
> This would be the case on Juno as well. But maybe at some point the
> X-Gene family would gain a CPU with such support.
> 
> Anyway, I would rather make 16K pages depend on EXPERT, make it a bit
> harder to enable. We've had a few questions recently about enabling it
> on CPUs that don't have such feature.

I thought there was also a suggestion that we could fail gracefully in
the EFI stub if we detected an unsupported page size?

Will