On Fri, 24 Sept 2021 at 15:49, Sebastian Andrzej Siewior
<bigeasy@xxxxxxxxxxxxx> wrote:
>
> Based on measurements the EFI functions get_variable /
> get_next_variable take up to 2us which looks okay.
> The functions get_time, set_time take around 10ms. These 10ms are too
> much. Even one ms would be too much.
> Ard mentioned that SetVariable might even trigger larger latencies if
> the firmware will erase flash blocks on NOR.
>
> The time-functions are used by efi-rtc and can be triggered during
> run-time (either via explicit read/write or ntp sync).
>
> The variable write could be used by pstore.
> These functions can be disabled without much of a loss. The poweroff /
> reboot hooks may be provided by PSCI.
>
> Disable EFI's runtime wrappers on PREEMPT_RT.
>
> This was observed on "EFI v2.60 by SoftIron Overdrive 1000".
>
> Acked-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> ---
> drivers/firmware/efi/efi.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index 847f33ffc4aed..39031cfcb6b92 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -66,7 +66,7 @@ struct mm_struct efi_mm = {
>
> struct workqueue_struct *efi_rts_wq;
>
> -static bool disable_runtime;
> +static bool disable_runtime = IS_ENABLED(CONFIG_PREEMPT_RT);
> static int __init setup_noefi(char *arg)
> {
> disable_runtime = true;
This is generic code and the commit log only talks about arm64. How
about other architectures?
