Hi Bagas, This mostly looks good to me. I have a couple of small comments below. On 9/9/25 6:57 PM, Bagas Sanjaya wrote: > From: Hugo Osvaldo Barrera <hugo@xxxxxxxxxxxxx> > > Since the Handover Protocol was deprecated, the recommended approach is > to provide an initrd using a UEFI boot service with the > LINUX_EFI_INITRD_MEDIA_GUID device path. Documentation for the new > approach has been no more than an admonition with a link to an existing > implementation. > > Provide a short explanation of this functionality, to ease future > implementations without having to reverse engineer existing ones. > > Signed-off-by: Hugo Osvaldo Barrera <hugo@xxxxxxxxxxxxx> > Link: https://lore.kernel.org/r/20250428131206.8656-2-hugo@xxxxxxxxxxxxx > [Bagas: Don't use :ref: link to EFI stub documentation] > Co-developed-by: Bagas Sanjaya <bagasdotme@xxxxxxxxx> > Signed-off-by: Bagas Sanjaya <bagasdotme@xxxxxxxxx> > --- > Documentation/admin-guide/efi-stub.rst | 3 +++ > Documentation/arch/x86/boot.rst | 35 ++++++++++++++++++++------ > 2 files changed, 30 insertions(+), 8 deletions(-) > > diff --git a/Documentation/admin-guide/efi-stub.rst b/Documentation/admin-guide/efi-stub.rst > index 090f3a185e1897..2f0f040f6913a4 100644 > --- a/Documentation/admin-guide/efi-stub.rst > +++ b/Documentation/admin-guide/efi-stub.rst > @@ -79,6 +79,9 @@ because the image we're executing is interpreted by the EFI shell, > which understands relative paths, whereas the rest of the command line > is passed to bzImage.efi. > > +.. hint:: > + It is also possible to provide an initrd using UEFI boot services. See > + :ref:`pe-coff-entry-point` for details. > > The "dtb=" option > ----------------- > diff --git a/Documentation/arch/x86/boot.rst b/Documentation/arch/x86/boot.rst > index 77e6163288db08..fadbe66517bdf2 100644 > --- a/Documentation/arch/x86/boot.rst > +++ b/Documentation/arch/x86/boot.rst > +.. _pe-coff-entry-point: > + > +PE/COFF entry point > +=================== > + > +When compiled with ``CONFIG_EFI_STUB=y``, the kernel can be executed as a > +regular PE/COFF binary. See Documentation/admin-guide/efi-stub.rst for > +implementation details. > + > +The stub loader can request the initrd via a UEFI protocol. For this to work, > +the firmware or bootloader needs to register a handle which implements the > +``EFI_LOAD_FILE2`` protocol with the ``LINUX_EFI_INITRD_MEDIA_GUID`` device > +path. In this case, a kernel booting via the EFI stub will use the ``LoadFile`` > +function on the registered handle to obtain a reference to the initrd. drivers/firmware/efi/libstub/efi-stub-helper.c (line 509) says LoadFile2 protocol. Is that the same as the LoadFile function? https://github.com/u-boot/u-boot/commit/ec80b4735a593961fe701cc3a5d717d4739b0fd0 (the link below) also says LoadFile2() 4 times (and LoadFile 0 times). thanks. -- ~Randy
