Clearing TTBCR.T1SZ explicitly when kernel runs on a configuration of
PHYS_OFFSET > PAGE_OFFSET.
Reading TTBCR in early boot stage might returns 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 without clearing TTBCR.T1SZ might risky
because the value doesn't have a reset value for TTBCR.T1SZ.
Signed-off-by: Hoeun Ryu <[email protected]>
---
arch/arm/mm/proc-v7-3level.S | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S
index 5e5720e..9ac2bec 100644
--- a/arch/arm/mm/proc-v7-3level.S
+++ b/arch/arm/mm/proc-v7-3level.S
@@ -140,6 +140,7 @@ ENDPROC(cpu_v7_set_pte_ext)
* otherwise booting secondary CPUs would end up using TTBR1 for the
* identity mapping set up in TTBR0.
*/
+ bichi \tmp, \tmp, #(1 << 16) @ clear TTBCR.T1SZ
orrls \tmp, \tmp, #TTBR1_SIZE @ TTBCR.T1SZ
mcr p15, 0, \tmp, c2, c0, 2 @ TTBCR
mov \tmp, \ttbr1, lsr #20
--
2.7.4
On Mon, Jun 05, 2017 at 06:22:20PM +0900, Hoeun Ryu wrote:
> diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S
> index 5e5720e..9ac2bec 100644
> --- a/arch/arm/mm/proc-v7-3level.S
> +++ b/arch/arm/mm/proc-v7-3level.S
> @@ -140,6 +140,7 @@ ENDPROC(cpu_v7_set_pte_ext)
> * otherwise booting secondary CPUs would end up using TTBR1 for the
> * identity mapping set up in TTBR0.
> */
> + bichi \tmp, \tmp, #(1 << 16) @ clear TTBCR.T1SZ
This looks insufficient. There's two bits here:
* TTBR0/TTBR1 split (PAGE_OFFSET):
* 0x40000000: T0SZ = 2, T1SZ = 0 (not used)
* 0x80000000: T0SZ = 0, T1SZ = 1
* 0xc0000000: T0SZ = 0, T1SZ = 2
but you seem to only be clearing one bit.
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
On Mon, Jun 5, 2017 at 6:34 PM, Russell King - ARM Linux
<[email protected]> wrote:
> On Mon, Jun 05, 2017 at 06:22:20PM +0900, Hoeun Ryu wrote:
>> diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S
>> index 5e5720e..9ac2bec 100644
>> --- a/arch/arm/mm/proc-v7-3level.S
>> +++ b/arch/arm/mm/proc-v7-3level.S
>> @@ -140,6 +140,7 @@ ENDPROC(cpu_v7_set_pte_ext)
>> * otherwise booting secondary CPUs would end up using TTBR1 for the
>> * identity mapping set up in TTBR0.
>> */
>> + bichi \tmp, \tmp, #(1 << 16) @ clear TTBCR.T1SZ
>
> This looks insufficient. There's two bits here:
>
> * TTBR0/TTBR1 split (PAGE_OFFSET):
> * 0x40000000: T0SZ = 2, T1SZ = 0 (not used)
> * 0x80000000: T0SZ = 0, T1SZ = 1
> * 0xc0000000: T0SZ = 0, T1SZ = 2
>
> but you seem to only be clearing one bit.
Oh, I'm sorry for the mistake, I'll fix this like #(7 << 16) in v2.
(There're 3 bits in TxSZ)
Thank you for the review.
>
> --
> RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
> FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
> according to speedtest.net.