Hi, Arnd & Ard, On Tue, Mar 1, 2022 at 6:19 PM Arnd Bergmann <arnd@xxxxxxxx> wrote: > > On Tue, Mar 1, 2022 at 5:17 AM Huacai Chen <chenhuacai@xxxxxxxxx> wrote: > > On Mon, Feb 28, 2022 at 7:35 PM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > > > On Mon, 28 Feb 2022 at 12:24, Arnd Bergmann <arnd@xxxxxxxx> wrote: > > > > On Mon, Feb 28, 2022 at 11:42 AM Huacai Chen <chenhuacai@xxxxxxxxx> wrote: > > > > Can't you just use the UEFI protocol for kernel entry regardless > > > > of the bootloader? It seems odd to use a different protocol for loading > > > > grub and the kernel, especially if that means you end up having to > > > > support both protocols inside of u-boot and grub, in order to chain-load > > > > a uefi application like grub. > > > > > > > > > > I think this would make sense. Now that the EFI stub has generic > > > support for loading the initrd via a UEFI specific protocol (of which > > > u-boot already carries an implementation), booting via UEFI only would > > > mean that no Linux boot protocol would need to be defined outside of > > > the kernel at all (i.e., where to load the kernel, where to put the > > > command line, where to put the initrd, other arch specific rules etc > > > etc) UEFI already supports both ACPI and DT boot > > > > After one night thinking, I agree with Ard that we can use RISCV-style > > fdt to support the raw elf kernel at present, and add efistub support > > after new UEFI SPEC released. > > I think that is the opposite of what Ard and I discussed above. Hmm, I thought that new UEFI SPEC is a requirement of efistub, maybe I'm wrong? > > > If I'm right, it seems that RISC-V passes a0 (hartid) and a1 (fdt > > pointer, which contains cmdline, initrd, etc.) to the raw elf kernel. > > And in my opinion, the main drawback of current LoongArch method > > (a0=argc a1=argv a2=bootparamsinterface pointer) is it uses a > > non-standard method to pass kernel args and initrd. So, can the below > > new solution be acceptable? > > > > a0=bootparamsinterface pointer (the same as a2 in current method) > > a1=fdt pointer (contains cmdline, initrd, etc., like RISC-V, I think > > this is the standard method) > > It would seem more logical to me to keep those details as part of the > interface between the EFI stub and the kernel, rather than the > documented boot interface. > > You said that there is already grub support using the UEFI > loader, so I assume you have a working draft of the boot > protocol. Are there still open questions about the interface > definition for that preventing you from using it as the only > way to enter the kernel from a bootloader? Things become simple if we only consider efistub rather than raw elf. But there are still some problems: 1, We want the first patch series as minimal as possible, efistub support will add a lot of code. 2, EFISTUB hides the interface between bootloader and raw kernel, but the interface does actually exist (efistub itself is also a bootloader, though it binds with the raw kernel). In the current implementation (a0=argc a1=argv a2=bootparaminterface), we should select EFI_GENERIC_STUB_INITRD_CMDLINE_LOADER which is marked as deprecated. Is this acceptable? If not, we still need to change the bootloader-kernel interface, maybe use the method in my previous email? 3, I know things without upstream means "nothing" for the community, but if we can provide raw elf kernel support to be compatible with existing products (not just a working draft, they are widely used now), it also seems reasonable. Huacai > > Arnd
