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

[Ard Biesheuvel]

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.