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Re: [PATCH 05/14] arm64: clean up THREAD_* definitions

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  Re: [PATCH 05/14] arm64: clean up THREAD_* definitions Catalin Marinas <catalin.marinas@arm.com> - 2017-08-14 14:10 +0200
    Re: [PATCH 05/14] arm64: clean up THREAD_* definitions Mark Rutland <mark.rutland@arm.com> - 2017-08-14 15:20 +0200

#1710883 — Re: [PATCH 05/14] arm64: clean up THREAD_* definitions

On Mon, Aug 07, 2017 at 07:35:56PM +0100, Mark Rutland wrote:
> Currently we define THREAD_SIZE and THREAD_SIZE order separately, with

s/THREAD_SIZE order/THREAD_SIZE_ORDER/

> the latter dependent on particular CONFIG_ARM64_*K_PAGES definitions.
> This is somewhat opaque, and will get in the way of future modifications
> to THREAD_SIZE.
> 
> This patch cleans this up, defining both in terms of a common
> THREAD_SHIFT, and using PAGE_SHIFT to calculate THREAD_SIZE_ORDER,
> rather than using a number of definitions dependent on config symbols.
> Subsequent patches will make use of this to alter the stack size used in
> some configurations.
> 
> At the same time, these are moved into <asm/memory.h>, which will avoid
> circular include issues in subsequent patches. To ensure that existing
> code isn't adversely affected, <asm/thread_info.h> is updated to
> transitively include these definitions.
> 
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: James Morse <james.morse@arm.com>
> Cc: Laura Abbott <labbott@redhat.com>
> Cc: Will Deacon <will.deacon@arm.com>
> ---
>  arch/arm64/include/asm/memory.h      | 8 ++++++++
>  arch/arm64/include/asm/thread_info.h | 9 +--------
>  2 files changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
> index 77d55dc..8ab4774 100644
> --- a/arch/arm64/include/asm/memory.h
> +++ b/arch/arm64/include/asm/memory.h
> @@ -102,6 +102,14 @@
>  #define KASAN_SHADOW_SIZE	(0)
>  #endif
>  
> +#define THREAD_SHIFT		14
> +
> +#if THREAD_SHIFT >= PAGE_SHIFT
> +#define THREAD_SIZE_ORDER	(THREAD_SHIFT - PAGE_SHIFT)
> +#endif
> +
> +#define THREAD_SIZE		(UL(1) << THREAD_SHIFT)

I haven't tried the series to this patch but it seems to me that
THREAD_SIZE_ORDER is undefined for a PAGE_SHIFT of 16. Without
VMAP_STACKS, it may fail to build.

-- 
Catalin

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#1710916

On Mon, Aug 14, 2017 at 12:59:59PM +0100, Catalin Marinas wrote:
> On Mon, Aug 07, 2017 at 07:35:56PM +0100, Mark Rutland wrote:
> > Currently we define THREAD_SIZE and THREAD_SIZE order separately, with
> 
> s/THREAD_SIZE order/THREAD_SIZE_ORDER/

Whoops; I'll fix that up now.

> > +#define THREAD_SHIFT		14
> > +
> > +#if THREAD_SHIFT >= PAGE_SHIFT
> > +#define THREAD_SIZE_ORDER	(THREAD_SHIFT - PAGE_SHIFT)
> > +#endif
> > +
> > +#define THREAD_SIZE		(UL(1) << THREAD_SHIFT)
> 
> I haven't tried the series to this patch but it seems to me that
> THREAD_SIZE_ORDER is undefined for a PAGE_SHIFT of 16. 

That is already the case without these patches, as we have:

#ifdef CONFIG_ARM64_4K_PAGES
#define THREAD_SIZE_ORDER       2
#elif defined(CONFIG_ARM64_16K_PAGES)
#define THREAD_SIZE_ORDER       0
#endif

... this is also deliberate, as we'd need an order of -2 with 16K stacks and
64K pages, and this doesn't make sense.

THREAD_SIZE_ORDER only matters if THREAD_SIZE >= PAGE_SIZE (or if we're using a
VMAP'd stack). For 64K pages && VMAP_STACK, we'll use a 64K stack, avoiding the
problem.

Thanks,
Mark.

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