Re: [PATCH] arm:lpae: build TTB control register value from scratch in v7_ttb_setup

[Russell King - ARM Linux]

On Sat, Jun 10, 2017 at 01:43:24PM +0900, Hoeun Ryu wrote:
> Hello, Russell and Robin.
> 
> Would you please review this patch ?

I think it's fine, thanks.

> 
> Than you
> 
> > On Jun 7, 2017, at 11:39 AM, Hoeun Ryu <hoeun.ryu@xxxxxxxxx> wrote:
> > 
> > Reading TTBCR in early boot stage might return the value of the previous
> > kernel's configuration, especially in case of kexec. For example, if
> > normal kernel (first kernel) had run on a configuration of PHYS_OFFSET <=
> > PAGE_OFFSET and crash kernel (second kernel) is running on a configuration
> > PHYS_OFFSET > PAGE_OFFSET, which can happen because it depends on the
> > reserved area for crash kernel, reading TTBCR and using the value to OR
> > other bit fields might be risky because it doesn't have a reset value for
> > TTBCR.
> > 
> > Suggested-by: Robin Murphy <robin.murphy@xxxxxxx>
> > Signed-off-by: Hoeun Ryu <hoeun.ryu@xxxxxxxxx>
> > ---
> > 
> > * v1: amended based on
> >          - "[PATCHv2] arm: LPAE: kexec: clear TTBCR.T1SZ explicitly when
> >             PHYS_OFFSET > PAGE_OFFSET"
> >          - https://lkml.org/lkml/2017/6/5/239
> > 
> > arch/arm/mm/proc-v7-3level.S | 3 +--
> > 1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S
> > index 5e5720e..7d16bbc 100644
> > --- a/arch/arm/mm/proc-v7-3level.S
> > +++ b/arch/arm/mm/proc-v7-3level.S
> > @@ -129,8 +129,7 @@ ENDPROC(cpu_v7_set_pte_ext)
> >    .macro    v7_ttb_setup, zero, ttbr0l, ttbr0h, ttbr1, tmp
> >    ldr    \tmp, =swapper_pg_dir        @ swapper_pg_dir virtual address
> >    cmp    \ttbr1, \tmp, lsr #12        @ PHYS_OFFSET > PAGE_OFFSET?
> > -    mrc    p15, 0, \tmp, c2, c0, 2        @ TTB control egister
> > -    orr    \tmp, \tmp, #TTB_EAE
> > +    mov    \tmp, #TTB_EAE            @ for TTB control egister
> >    ALT_SMP(orr    \tmp, \tmp, #TTB_FLAGS_SMP)
> >    ALT_UP(orr    \tmp, \tmp, #TTB_FLAGS_UP)
> >    ALT_SMP(orr    \tmp, \tmp, #TTB_FLAGS_SMP << 16)
> > -- 
> > 2.7.4
> > 
> 
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