2017-06-07 02:45:09

by Hoeun Ryu

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

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 <[email protected]>
Signed-off-by: Hoeun Ryu <[email protected]>
---

* 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

2017-06-10 04:43:31

by Hoeun Ryu

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

Hello, Russell and Robin.

Would you please review this patch ?

Than you

> On Jun 7, 2017, at 11:39 AM, Hoeun Ryu <[email protected]> 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 <[email protected]>
> Signed-off-by: Hoeun Ryu <[email protected]>
> ---
>
> * 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
>

2017-06-10 10:19:53

by Russell King (Oracle)

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

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 <[email protected]> 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 <[email protected]>
> > Signed-off-by: Hoeun Ryu <[email protected]>
> > ---
> >
> > * 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
> >
>
> _______________________________________________
> linux-arm-kernel mailing list
> [email protected]
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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