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

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Message-ID: <CABb+yY1VsEwDi5XCRkKbSNPW_+_MgL4gdAChKgX_NGHRzXq6qw@mail.gmail.com>
Date:	Wed, 27 Aug 2014 21:15:24 +0530
From:	Jassi Brar <jassisinghbrar@...il.com>
To:	Konstantin Khlebnikov <koct9i@...il.com>
Cc:	Will Deacon <will.deacon@....com>,
	Konstantin Khlebnikov <k.khlebnikov@...sung.com>,
	Russell King <linux@....linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Vitaly Andrianov <vitalya@...com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/2] ARM: LPAE: load upper bits of early TTBR0/TTBR1

On Wed, Aug 27, 2014 at 9:01 PM, Konstantin Khlebnikov <koct9i@...il.com> wrote:
> On Wed, Aug 27, 2014 at 7:26 PM, Jassi Brar <jassisinghbrar@...il.com> wrote:
>> On Tue, Jul 29, 2014 at 5:59 PM, Konstantin Khlebnikov <koct9i@...il.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
>>>>> >> +     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
>>>>> >
>>>>> > I must admit, the code you are removing here looks really strange. Was there
>>>>> > a badly resolved conflict somewhere along the way? It would be nice to see
>>>>> > if your fix (which seems ok to me) was actually present in the mailing list
>>>>> > posting of the patch that ended in the above mess.
>>>>>
>>>>> Nope, no merge conflicts, source in original patch
>>>>> https://lkml.org/lkml/2012/9/11/346
>>>>>
>>>>> That mess completely harmless, this code is used only once on boot.
>>>>> I don't have that email, so replying isn't trivial for me.
>>>>
>>>> How bizarre. Also, Cyril doesn't work for TI anymore (his email is
>>>> bouncing), so it's tricky to know what he meant here.
>>>>
>>>> Your patch looks better than what we currently have though. Have you managed
>>>> to test it on a keystone platform (I don't have one)?
>>>
>>> No, I don't have it too. As well as I don't have direct access to the
>>> platform where
>>> problem was found. I've debugged this in patched qemu.
>>>
>> It seems the patch wasn't tested on any real platform, I did on my
>> CA15 based platform - it breaks boot. Simply reverting the patch gets
>> it going again. I am happy to try any fix.
>>
>
> Please try to remove adcls line.
> Seems like this affects only systems where PHYS_OFFSET == PAGE_OFFSET.
>
> --- a/arch/arm/mm/proc-v7-3level.S
> +++ b/arch/arm/mm/proc-v7-3level.S
> @@ -146,7 +146,6 @@ 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
> -       adcls   \tmp, \tmp, #0
>         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
>
Yup, restores boot.

Thanks
Jassi
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