Re: Safe-mode on amd64 broken

on 29/09/2010 13:40 Alexander Motin said the following:
> Hi.
> 
> David Naylor wrote:
>> Trying to boot a recent (sep 23) amd64 kernel in safe-mode fails with ``panic: 
>> No usable event timer found!''.  This occurs on two (all my) machines.  This 
>> has been a persistent problem since the introduction of the event timer code.  
> 
> I've reproduced the problem.
> 
> The reason is that all (or at least most) of devices (both PCI and ISA),
> including only available in that mode i8254 and RTC timers, failed to
> allocate their interrupts. While reported message is indeed related to
> event timer code, problem IMHO doesn't. While without this panic system
> could boot without any alive timer, I have doubts that it would be
> functional without timers, USB, network and disk controllers.
> 
> Problems seems to be the same if I am trying to boot without ACPI.
> 

It's interesting to see what the "Safe Mode" really is:
dup bootsafekey _at_ = if
        s" arch-i386" environment? if
                drop
                s" acpi_load" unsetenv
                s" 1" s" hint.acpi.0.disabled" setenv
                s" 1" s" loader.acpi_disabled_by_user" setenv
                s" 1" s" hint.apic.0.disabled" setenv
        then
        s" 0" s" hw.ata.ata_dma" setenv
        s" 0" s" hw.ata.atapi_dma" setenv
        s" 0" s" hw.ata.wc" setenv
        s" 0" s" hw.eisa_slots" setenv
        s" 1" s" hint.kbdmux.0.disabled" setenv
        0 boot


Not sure if disabling ACPI on modern hardware is a good idea.
Even more unsure about disabling APIC.

Makes me wonder what this could be useful for.
Perhaps, these are just leftovers from times were ACPI, APIC (and ATA DMA) were
all new and unproven things.

-- 
Andriy Gapon