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

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Date:	Wed, 27 Aug 2014 19:31:29 +0400
From:	Konstantin Khlebnikov <koct9i@...il.com>
To:	Jassi Brar <jassisinghbrar@...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>,
	Cyril Chemparathy <cyril@...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 7:26 PM, Jassi Brar <jassisinghbrar@...il.com> wrote:
> On Tue, Jul 29, 2014 at 5:59 PM, Konstantin Khlebnikov <koct9i@...il.com> wrote:
>> On Mon, Jul 28, 2014 at 10:47 PM, Will Deacon <will.deacon@....com> wrote:
>>> On Mon, Jul 28, 2014 at 07:40:58PM +0100, Konstantin Khlebnikov wrote:
>>>> On Mon, Jul 28, 2014 at 10:12 PM, Will Deacon <will.deacon@....com> wrote:
>>>> > On Tue, Jul 22, 2014 at 04:36:23PM +0100, Konstantin Khlebnikov 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


> Thanks
> Jassi
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