On Tue, 20 Sept 2022 at 03:45, Huacai Chen <chenhuacai@xxxxxxxxxx> wrote: > > Hi, Ard, > ... > I'm very sorry, after an offline discussion with my colleagues, > non-EFI DT boot is still needed (very sadly, we want to drop non-EFI > firmware but we can't do that). However, for non-EFI DT boot we will > use the same parameter passing method (a0=efi boot flag, a1=cmdline, > a2=systemtable), firmware will generate a simple systemtable only for > DT. In this way all boot methods share the same logic, and also make > kexec easy to implement. > OK, that should work. So I suppose you create a EFI system table along with EFI configuration tables for DT, SMBIOS, etc? In this case, I suggest you omit the MEMMAP config table that I am adding here, so that there is no ambiguity between the EFI provided memory map and the one provided by DT. I think that should be a clean way to implement this. > So, let's make a0 the real "efi boot flag" and let it control > EFI_BOOT, for efistub, we can just pass "true" unconditionally > (whether support efi_novamap is not as important as the efi boot flag > for us, as you said, efi_novamap is just for broken firmware). Indeed. So as before, I will just set efi_novamap to false. You can still use noefi or efi=noruntime to turn off the EFI runtime pieces if needed (e.g., PREEMPT_RT tends to disable those by default to preserve their bounded worst case latency)
