Hi, Ard & Arnd, On Thu, Mar 3, 2022 at 5:54 PM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > > On Thu, 3 Mar 2022 at 07:26, Huacai Chen <chenhuacai@xxxxxxxxx> wrote: > > > > Hi, Ard & Arnd, > > > > On Wed, Mar 2, 2022 at 5:20 PM Huacai Chen <chenhuacai@xxxxxxxxx> wrote: > > > > > > Hi, Ard, > > > > > > On Wed, Mar 2, 2022 at 4:58 PM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > > > > > > > > On Wed, 2 Mar 2022 at 09:56, Huacai Chen <chenhuacai@xxxxxxxxx> wrote: > > > > > > > > > > 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? > > > > > > > > Why do you need this? > > > Because in the current implementation (a0=argc a1=argv > > > a2=bootparaminterface), initrd should be passed by cmdline > > > (initrd=xxxx). If without that option, efi_load_initrd_cmdline() will > > > not call handle_cmdline_files(). > > It seems I'm wrong. EFI_GENERIC_STUB_INITRD_CMDLINE_LOADER controls > > "initrd=xxxx" from BIOS to EFISTUB, but has nothing to do with > > a0/a1/a2 usage (which controls the "initrd=xxxx" from efistub to raw > > kernel). The real reason is our UEFI BIOS has an old codebase without > > LoadFile2 support. > > > > The problem with initrd= is that it can only load the initrd from the > same EFI block device that the kernel was loaded from, which is highly > restrictive, and doesn't work with bootloaders that call LoadImage() > on a kernel image loaded into memory. This is why x86 supports passing > the initrd in memory, and provide the base/size via struct bootparams, > and arm64 supports the same using DT. > > The LoadImage2 protocol based method intends to provide a generic > alternative to this, as it uses a pure EFI abstraction, and therefore > does not rely on struct bootparams or DT at all. > > So the LoadImage2() based method is preferred, but if your > architecture implements DT support already, there is nothing > preventing you from passing initrd information directly to the kernel > via the /chosen node. > > > Then, my new questions are: > > 1, Is EFI_GENERIC_STUB_INITRD_CMDLINE_LOADER an unacceptable option > > for a new Arch? If yes, we should backport LoadFile2 support to our > > BIOS. > > See above. > > > 2, We now all agree that EFISTUB is the standard and maybe the only > > way in future. But, can we do the efistub work in the second series, > > in order to make the first series as minimal as possible? (I will > > update the commit message to make it clear that a0/a1/a2 usage is only > > an internal interface between efistub and raw kernel). > > > > I think it would be better to drop the UEFI and ACPI pieces for now, > and resubmit it once the dust has settled around this. FDT support is our future goal, at present we only have ACPI firmware and kernel. I mentioned FDT just wants to replace a0/a1 to pass cmdline, not means we already have FDT support. So, let's keep the existing a0/a1/a2 usage as an internal interface for now, then backport LoadFile2 and add efistub support. Huacai
