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Date: Thu, 6 Dec 2018 15:31:29 +0000
From: Russell King - ARM Linux <linux@armlinux.org.uk>
To: Krzysztof Kozlowski <krzk@kernel.org>
Subject: Re: [PATCH v2 5/5] ARM: spectre-v2: per-CPU vtables to work around
 big.Little systems
Message-ID: <20181206153128.GW30658@n2100.armlinux.org.uk>
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On Thu, Dec 06, 2018 at 04:03:27PM +0100, Krzysztof Kozlowski wrote:
> On Thu, 6 Dec 2018 at 15:37, Russell King - ARM Linux
> <linux@armlinux.org.uk> wrote:
> >
> > On Thu, Dec 06, 2018 at 03:30:22PM +0100, Krzysztof Kozlowski wrote:
> > > On Thu, 6 Dec 2018 at 15:07, Russell King - ARM Linux
> > > > That basically means that the dcache_clean_area method for CPU1
> > > > differs from the dcache_clean_area method for CPU0.  If all your
> > > > CPUs are identical, that definitely should not be happening.
> > > >
> > > > Hmm.  Interestingly, OMAP4430 passes hotplug tests just fine.
> > > >
> > > > Please try this patch.
> > >
> > > This fixes both hotplug and suspend to RAM. I was trying to narrow why
> > > the pointers to all processor functions differ. During first boot they
> > > were OK but it seems they were changed just before suspend.
> >
> > Thanks for testing.  I think this is probably a better patch which
> > should end up with the same result.
> >
> > I suspect no one else has noticed because most people have big.Little
> > support disabled - that'd explain why it doesn't show up on OMAP4.
> >
> > diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S
> > index 81d0efb055c6..44f9776139a8 100644
> > --- a/arch/arm/mm/proc-macros.S
> > +++ b/arch/arm/mm/proc-macros.S
> > @@ -274,6 +274,13 @@
> >         .endm
> >
> >  .macro define_processor_functions name:req, dabort:req, pabort:req, nommu=0, suspend=0, bugs=0
> > +/*
> > + * If we are building for big.Little with branch predictor hardening,
> > + * we need the processor function tables to remain available after boot.
> > + */
> > +#if defined(CONFIG_BIG_LITTLE) && defined(CONFIG_HARDEN_BRANCH_PREDICTOR)
> > +       .rodata
> > +#endif
> >         .type   \name\()_processor_functions, #object
> >         .align 2
> >  ENTRY(\name\()_processor_functions)
> > @@ -309,6 +316,9 @@ ENTRY(\name\()_processor_functions)
> >         .endif
> >
> >         .size   \name\()_processor_functions, . - \name\()_processor_functions
> > +#if defined(CONFIG_BIG_LITTLE) && defined(CONFIG_HARDEN_BRANCH_PREDICTOR)
> > +       .previous
> > +#endif
> >  .endm
> >
> >  .macro define_cache_functions name:req
> 
> Does not compile:
> ../arch/arm/mm/proc-v7.S: Assembler messages:
> ../arch/arm/mm/proc-v7.S:560: Error: unknown pseudo-op: `.rodata'
> ../arch/arm/mm/proc-v7.S:575: Error: unknown pseudo-op: `.rodata'
> ../arch/arm/mm/proc-v7.S:596: Error: unknown pseudo-op: `.rodata'
> ../arch/arm/mm/proc-v7.S:611: Error: unknown pseudo-op: `.rodata'
> ../arch/arm/mm/proc-v7.S:629: Error: unknown pseudo-op: `.rodata'

It should be .section ".rodata", sorry.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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