linux-kernel - Re: [PATCH 1/2] ARM: LPAE: load upper bits of early TTBR0/TTBR1

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Date:	Tue, 5 Aug 2014 19:42:32 +0400
From:	Konstantin Khlebnikov <koct9i@...il.com>
To:	Konstantin Khlebnikov <k.khlebnikov@...sung.com>
Cc:	Russell King <linux@....linux.org.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Will Deacon <will.deacon@....com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Vitaly Andrianov <vitalya@...com>,
	Cyril Chemparathy <cyril@...com>
Subject: Re: [PATCH 1/2] ARM: LPAE: load upper bits of early TTBR0/TTBR1

On Tue, Jul 22, 2014 at 7:36 PM, Konstantin Khlebnikov
<k.khlebnikov@...sung.com> wrote:
> This patch fixes booting when idmap pgd lays above 4gb. Commit
> 4756dcbfd37 mostly had fixed this, but it'd failed to load upper bits.
>
> Also this fixes adding TTBR1_OFFSET to TTRR1: if lower part overflows
> carry flag must be added to the upper part.
>
> Signed-off-by: Konstantin Khlebnikov <k.khlebnikov@...sung.com>
> Cc: Cyril Chemparathy <cyril@...com>
> Cc: Vitaly Andrianov <vitalya@...com>
> ---
>  arch/arm/mm/proc-v7-3level.S |    7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S
> index 22e3ad6..f0481dd 100644
> --- a/arch/arm/mm/proc-v7-3level.S
> +++ b/arch/arm/mm/proc-v7-3level.S
> @@ -140,12 +140,11 @@ ENDPROC(cpu_v7_set_pte_ext)
>         mov     \tmp, \ttbr1, lsr #(32 - ARCH_PGD_SHIFT)        @ upper bits
>         mov     \ttbr1, \ttbr1, lsl #ARCH_PGD_SHIFT             @ lower bits
>         addls   \ttbr1, \ttbr1, #TTBR1_OFFSET
> -       mcrr    p15, 1, \ttbr1, \zero, c2                       @ load TTBR1
> +       adcls   \tmp, \tmp, #0


Oops, this carry fixup is wrong. addls above doesn't set carry flag.


> +       mcrr    p15, 1, \ttbr1, \tmp, c2                        @ load TTBR1
>         mov     \tmp, \ttbr0, lsr #(32 - ARCH_PGD_SHIFT)        @ upper bits
>         mov     \ttbr0, \ttbr0, lsl #ARCH_PGD_SHIFT             @ lower bits
> -       mcrr    p15, 0, \ttbr0, \zero, c2                       @ load TTBR0
> -       mcrr    p15, 1, \ttbr1, \zero, c2                       @ load TTBR1
> -       mcrr    p15, 0, \ttbr0, \zero, c2                       @ load TTBR0
> +       mcrr    p15, 0, \ttbr0, \tmp, c2                        @ load TTBR0
>         .endm
>
>         /*
>
> --
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