Re: [PATCH 1/4] KVM: arm64: Enable Pointer Authentication at EL2 if available

Marc Zyngier
2020-06-15T10:45:16Z

Hi Andrew,

On 2020-06-15 09:48, Andrew Scull wrote:
> On Mon, Jun 15, 2020 at 09:19:51AM +0100, Marc Zyngier wrote:
>> While initializing EL2, switch Pointer Authentication if detected
>
> ^ nit: on?

Yes.

>
>> from EL1. We use the EL1-provided keys though.
>>
>> Signed-off-by: Marc Zyngier <maz@kernel.org>
>> ---
>> arch/arm64/kvm/hyp-init.S | 11 +++++++++++
>> 1 file changed, 11 insertions(+)
>>
>> diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
>> index 6e6ed5581eed..81732177507d 100644
>> --- a/arch/arm64/kvm/hyp-init.S
>> +++ b/arch/arm64/kvm/hyp-init.S
>> @@ -104,6 +104,17 @@ alternative_else_nop_endif
>> */
>> mov_q x4, (SCTLR_EL2_RES1 | (SCTLR_ELx_FLAGS & ~SCTLR_ELx_A))
>> CPU_BE( orr x4, x4, #SCTLR_ELx_EE)
>> +alternative_if ARM64_HAS_ADDRESS_AUTH_ARCH
>> + b 1f
>> +alternative_else_nop_endif
>> +alternative_if_not ARM64_HAS_ADDRESS_AUTH_IMP_DEF
>> + b 2f
>> +alternative_else_nop_endif
>> +1:
>> + orr x4, x4, #(SCTLR_ELx_ENIA | SCTLR_ELx_ENIB)
>> + orr x4, x4, #SCTLR_ELx_ENDA
>> + orr x4, x4, #SCTLR_ELx_ENDB
>
> mm/proc.S builds the mask with ldr and ors it in one go, would be nice
> to use the same pattern.

Do you actually mean kernel/head.S, or even __ptrauth_keys_init_cpu in
asm/asm_pointer_auth.h?

If so, I agree that it'd be good to make it look similar by using the
mov_q macro, at the expense of a spare register (which we definitely can
afford here).

Thanks,

M.
--
Jazz is not dead. It just smells funny...