[PATCH v2 3/4] arm64: arch_timer: Disable the compat vdso for cores affected by ARM64_WORKAROUND_1418040

[Mark Rutland]

On Mon, Jul 06, 2020 at 05:38:01PM +0100, Marc Zyngier wrote:
> ARM64_WORKAROUND_1418040 requires that AArch32 EL0 accesses to
> the virtual counter register are trapped and emulated by the kernel.
> This makes the vdso pretty pointless, and in some cases livelock
> prone.
> 
> Provide a workaround entry that limits the vdso to 64bit tasks.
> 
> Cc: stable at vger.kernel.org
> Signed-off-by: Marc Zyngier <maz at kernel.org>

Acked-by: Mark Rutland <mark.rutland at arm.com>

Mark.

> ---
>  drivers/clocksource/arm_arch_timer.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
> index a8e4fb429f52..6c3e84180146 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -480,6 +480,14 @@ static const struct arch_timer_erratum_workaround ool_workarounds[] = {
>  		.set_next_event_virt = erratum_set_next_event_tval_virt,
>  	},
>  #endif
> +#ifdef CONFIG_ARM64_ERRATUM_1418040
> +	{
> +		.match_type = ate_match_local_cap_id,
> +		.id = (void *)ARM64_WORKAROUND_1418040,
> +		.desc = "ARM erratum 1418040",
> +		.disable_compat_vdso = true,
> +	},
> +#endif
>  };
>  
>  typedef bool (*ate_match_fn_t)(const struct arch_timer_erratum_workaround *,
> -- 
> 2.27.0
>