On 2022-04-01 00:19:57 [+0200], Javier Martinez Canillas wrote: > > In case of (CONFIG_PREEMPT_RT=y && CONFIG_EFI_DISABLE_RUNTIME=n), > > shouldn't we add a small message in the kernel log warning that EFI > > runtime services are enabled for the RT kernel? > > > > In almost all HW, except custom ones with "verified" firmware, such a > > warning would be useful... This is especially true since in the embedded > > I considered that as well but was not sure about what that message should be. This makes sense and we had this in the past but dropped it for some reason. > Since it will be printed even on systems whose EFI firmwares do not > have such long call times as the ones described in the commit that > disabled the runtime services for RT. > > And in that case the warning may be misleading and make users believe > that a problem exists, which might not be accurate. Does this matter? The efi-rtc driver is known to cause latencies but it does not happen if the driver is not used. The same is probably true for efi-vars: It won't cause high latencies on _read_ but then a certain number of bit flips during read _may_ lead to write+erase which will cause higher latencies. Having a warning at boot (similar to trace_printk's warning) with the options listed that are known to case high latencies might be a help. There are some options that nobody will argue about like LOCKDEP. Then there are other like WATCHDOG or this one, where a debate might start ;) > Best regards, > Javier Sebastian
