Re: [PATCH RFC/RFT 0/3] Add grub loader support for RISC-V Linux

[Atish Patra]

On Mon, Apr 27, 2020 at 3:11 PM Ard Biesheuvel <address@hidden> wrote:
>
> On Mon, 27 Apr 2020 at 23:16, Heinrich Schuchardt <address@hidden> wrote:
> >
> > Am April 27, 2020 8:58:57 PM UTC schrieb Heinrich Schuchardt 
> > <address@hidden>:
> > >Am April 27, 2020 8:52:43 PM UTC schrieb Ard Biesheuvel
> > ><address@hidden>:
> > >>On Mon, 27 Apr 2020 at 22:47, Ard Biesheuvel <address@hidden> wrote:
> > >>>
> > >>> On Mon, 27 Apr 2020 at 22:47, Heinrich Schuchardt
> > >><address@hidden> wrote:
> > >>> >
> > >>> > Am April 27, 2020 7:39:38 PM UTC schrieb Ard Biesheuvel
> > >><address@hidden>:
> > >>> > >On Mon, 27 Apr 2020 at 21:36, Heinrich Schuchardt
> > >><address@hidden>
> > >>> > >wrote:
> > >>> > >>
> > >>> > >> On 4/27/20 1:01 PM, Daniel Kiper wrote:
> > >>> > >> > On Mon, Apr 27, 2020 at 08:15:41AM +0200, Ard Biesheuvel
> > >>wrote:
> > >>> > >> >> On Sun, 26 Apr 2020 at 21:40, Atish Patra
> > >><address@hidden>
> > >>> > >wrote:
> > >>> > >> >>>
> > >>> > >> >>> This series adds grub loader support for RISC-V Linux.
> > >>Thanks to
> > >>> > >the awesome
> > >>> > >> >>> initial RISC-V support added by Alex, we just needed a
> > >>loader for
> > >>> > >RISC-V to
> > >>> > >> >>> load and execute Linux using UEFI protocol.
> > >>> > >> >>>
> > >>> > >> >>> Fortunately, ARM64 Linux loader is written in an
> > >>architecture
> > >>> > >agnostic manner
> > >>> > >> >>> so thatgeneric RISC-V can easily reuse the loader code.
> > >>Thus, the
> > >>> > >first patch
> > >>> > >> >>> just moves the ARM64 code to common code. I have compile
> > >>tested
> > >>> > >for
> > >>> > >> >>> ARM64/ARM32. Even though it doesn't introduce any
> > >functional
> > >>> > >change
> > >>> > >> >>> for ARM/ARM64, any real testing will be helpful.
> > >>> > >> >>
> > >>> > >> >> May I suggest that we not blindly adopt the ARM code here,
> > >>but
> > >>> > >> >> instead, use the new initrd loading protocol that removes
> > >the
> > >>need
> > >>> > >for
> > >>> > >> >> GRUB to modify or even know about the device tree at all?
> > >>> > >>
> > >>> > >> Does this protocol exist in EDK2 by now?
> > >>> > >>
> > >>> > >
> > >>> > >Yes. It exists as a shell command, and as a load option for OVMF.
> > >>> > >
> > >>> > >> In U-Boot there is a basic implementation which can provide a
> > >>single
> > >>> > >> initrd image with a hardcoded file name. The file_path argument
> > >>> > >passed
> > >>> > >> to U-Boot is ignored due to Ilias' security concerns when he
> > >>wrote
> > >>> > >the
> > >>> > >> patch.
> > >>> > >>
> > >>> > >> GRUB is only needed if we have multiple kernels to choose from
> > >>with
> > >>> > >> distinct initial ramdisks.
> > >>> > >>
> > >>> > >> Please, describe what you expect the initrd loading protocol to
> > >>do
> > >>> > >when
> > >>> > >> called from GRUB. How will the ramdisk fitting the kernel
> > >chosen
> > >>in
> > >>> > >GRUB
> > >>> > >> be identified?
> > >>> > >>
> > >>> > >
> > >>> > >The same what GRUB's 'initrd' command does. Whichever initrd you
> > >>> > >select with it is the one that gets returned by the protocol.
> > >>> >
> > >>> > Will GRUB provide the absolute device path in parameter file_path?
> > >>> >
> > >>>
> > >>> Which parameter 'file_path" is that?
> > >>
> > >>Ah, I guess you mean the LoadFile2 argument? That is always
> > >>end-of-device-path in this case, since the initrd device path only
> > >>consists of the vendor media GUID.
> > >>
> > >>The thing to keep in mind here is that the OS does not *choose* an
> > >>initrd, it simply loads the one that the bootloader has staged for it.
> > >
> > >How should U-Boot know which initrd fits the kernel chosen by the user
> > >in GRUB? That information exists in grub.cfg only.
> > >
> > >If GRUB cannot provide this information, what is GRUB's added value in
> > >the boot process?
> >
> > Hello Ard,
> >
> > Did I misunderstand you and you want to provide a LOAD_FILE2 implementation 
> > in GRUB and not use the one in the firmware?
> >
>
> Yes. If you use GRUB, it is provided by GRUB. Otherwise, it can be
> provided by U-Boot or EDK2.
>

Thanks for the discussion. I got clarification as well.
I will work on adding LOAD_FILE2 support in GRUB.

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-- 
Regards,
Atish