Re: [PATCH] ARM: spectre-v2: Try to set IBE bit for Cortex-A15 and Brahma-B15
From: Marek Vasut
Date: Wed Aug 22 2018 - 16:21:46 EST
On 08/11/2018 03:58 PM, Marek Vasut wrote:
> On 06/08/2018 12:58 AM, Florian Fainelli wrote:
>> Per the ARM reference manual for the Cortex-A15, The ACTLR:
>> Is a read/write register.
>> Common to the Secure and Non-secure states.
>> Is only accessible from PL1 or higher, with access rights that depend
>> on the mode:
>> * Read/write in Secure PL1 modes.
>> * Read-only and write-ignored in Non-secure PL1 and PL2 modes
>> if NSACR.NS_SMP is 0.
>> * Read/write in Non-secure PL1 and PL2 modes if NSACR.NS_SMP
>> is 1. In this case, all bits are write-ignored except for the SMP bit.
>> We can attempt to set this bit from within the kernel, which helps
>> avoiding firmware side modifications to set the IBE bit when that is
>> impractical. We do this within __v7_ca15mp_setup and __v7_b15mp_setup
>> because by then we already took those labels because the processors we
>> run on do match.
>> Signed-off-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
> I believe this would help on selected R-Car Gen2 SoCs which have CA15
> cores. Those cores are released from reset by Linux directly and jump to
> the reset vector set up by Linux in Secure mode.
> I was looking for a generic solution after discussing how to mitigate
> the spectrev2 on such SoCs with Catalin on IRC and this seems to be one
> option. There was also a suggestion that Russell is working on some sort
> of generic solution too. Can you comment on that please ?
Is there any feedback on this ?
>> arch/arm/mm/proc-v7.S | 8 +++++++-
>> 1 file changed, 7 insertions(+), 1 deletion(-)
>> diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
>> index 6fe52819e014..a21cf3729efa 100644
>> --- a/arch/arm/mm/proc-v7.S
>> +++ b/arch/arm/mm/proc-v7.S
>> @@ -284,10 +284,16 @@ __v7_cr8mp_setup:
>> b 1f
>> + b 2f
>> +#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
>> + mrc p15, 0, r0, c1, c0, 1
>> + orr r0, r0, #1 @ Enable IBE bit
>> + mcr p15, 0, r0, c1, c0, 1
>> - mov r10, #0
>> +2: mov r10, #0
>> 1: adr r0, __v7_setup_stack_ptr
>> ldr r12, [r0]
>> add r12, r12, r0 @ the local stack