[PATCH 1/3] arm64: merge __enable_mmu and __turn_mmu_on

Christopher Covington
2015-03-17T17:39:50Z

On 03/17/2015 06:11 AM, Ard Biesheuvel wrote:
> Enabling of the MMU is split into two functions, with an align and
> a branch in the middle. On arm64, the entire kernel Image is ID mapped
> so this is really not necessary, and we can just merge it into a
> single function.
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
> arch/arm64/kernel/head.S | 30 ++++++++----------------------
> 1 file changed, 8 insertions(+), 22 deletions(-)
>
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index 65c7de889c8c..fb912314d5e1 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -615,8 +615,13 @@ ENDPROC(__secondary_switched)
> #endif /* CONFIG_SMP */
>
> /*
> - * Setup common bits before finally enabling the MMU. Essentially this is just
> - * loading the page table pointer and vector base registers.
> + * Enable the MMU. This completely changes the structure of the visible memory
> + * space. You will not be able to trace execution through this.

I don't understand the last sentence. I recall being able to read and
eventually understand simulator instruction traces of this code. Is the
sentence referring to the Embedded Trace Macrocell or something?

Chris

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