Re: [PATCH] efi: Allow to enable EFI runtime services with PREEMPT_RT

[Javier Martinez Canillas]

Hello Sebastian,

On 3/31/22 16:13, Sebastian Andrzej Siewior wrote:
> On 2022-03-31 16:10:38 [+0200], Javier Martinez Canillas wrote:
>> Commit d9f283ae71af ("efi: Disable runtime services on RT") disabled EFI
>> runtime services when the CONFIG_PREEMPT_RT option is enabled.
>>
>> The rationale for the change is that some EFI calls could take too much
>> time, leading to large latencies which are an issue for RT kernels.
>>
>> But a side effect of that commit is that now is not possible anymore to
>> enable the EFI runtime services by default when CONFIG_PREEMPT_RT is set
>> to y, even for platforms that could guarantee bounded time for EFI calls.
>>
>> Instead, let's add a new EFI_DISABLE_RUNTIME boolean Kconfig option, that
>> would be set to n by default but to y if CONFIG_PREEMPT_RT is enabled.
>>
>> That way, the current behaviour is preserved but gives users a mechanism
>> to enable the EFI runtimes services in their kernels if that is required.
> 
> Is the command line switch
> 	efi=runtime
> 
> not working?
>

Yes, it is but the motivation is to be able to have EFI runtime services
by default without the need for any kernel command line parameter.

In the same vein, I could ask if efi=noruntime wasn't enough instead of
commit ("efi: Disable runtime services on RT").

-- 
Best regards,

Javier Martinez Canillas
Linux Engineering
Red Hat