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.faine...@gmail.com>
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 ? > --- > 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 > __v7_ca7mp_setup: > __v7_ca12mp_setup: > + b 2f > __v7_ca15mp_setup: > __v7_b15mp_setup: > +#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 > +#endif > __v7_ca17mp_setup: > - mov r10, #0 > +2: mov r10, #0 > 1: adr r0, __v7_setup_stack_ptr > ldr r12, [r0] > add r12, r12, r0 @ the local stack > -- Best regards, Marek Vasut
