[PATCH 0/4] introduce EFI_RAM_DISK_PROTOCOL

[Masahisa Kojima]

Hi Heinrich,

On Fri, 7 Jul 2023 at 15:34, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>
> On 7/7/23 06:00, Masahisa Kojima wrote:
> > This series introduces the EFI_RAM_DISK_PROTOCOL implementation.
> > The major purpose of this series is a preparation for EFI HTTP(S) boot.
> >
> > Now U-Boot can download the distro installer ISO image
> > via wget or tftpboot commands, but U-Boot can not mount
> > the downloaded ISO image.
> > By calling EFI_RAM_DISK_PROTOCOL->register API, user can
> > mount the ISO image and boot the distro installer.
>
> If I understand you correctly, with your design RAM disks will only
> exist in the EFI sub-system.

Yes, RAM disk can be accessed through the EFI sub-system.

>
> We strive to synchronize what is happening on the driver model level and
> on the UEFI level. I would prefer a design where we have a UCLASS_BLK
> driver ram disks and the EFI_RAM_DISK_PROTOCOL is a one method of
> managing ram disk devices.

The current EFI_RAM_DIISK_PROTOCOL implementation is the same as what
EDK2 reference
implementation does, and I'm not yet fully convinced how much the
native U-Boot gets the benefit
of RAM disk support.

>
> A big issue we have is RAM management. malloc() can only assign limited
> amount of memory which is probably too small for the RAM disk you are
> looking at. We manage page sized memory in the EFI sub-system but this
> is not integrated with the LMB memory checks.

OK, when we think about EFI HTTP boot and hand-off the RAM disk to the kernel,
we need to consider the memory allocation for the big ISO image.
But as far as EFI_RAM_DISK_PROTOCOL is concerned, can we leave
the memory management issue?

Thanks,
Masahisa Kojima

>
> The necessary sequence of development is probably:
>
> * Rework memory management
> * Implement ramdisks as UCLASS_BLK driver
> * Implement the EFI_RAM_DISK_PROTOCOL based on the UCLASS_BLK driver.
>
> Best regards
>
> Heinrich
>
> >
> > Note that the installation process may not proceed
> > after the distro installer calls ExitBootServices()
> > since there is no hand-off process for the block device of
> > memory mapped ISO image.
> >
> > The EFI_RAM_DISK_PROTOCOL was tested with the
> > debian network installer[1] on qemu_arm64 platform.
> > The example procedure is as follows.
> >   => tftpboot 41000000 mini.iso
> >   => efidebug disk load 41000000 $filesize
> >
> > After these commands, ISO image is mounted like:
> >
> >   => efidebug dh
> >
> >      000000007eec5910 (efiblk#0)
> >        /RamDisk(0x41000000,4974afff,3d5abd30-4175-87ce-6d64-d2ade523c4bb,0x0)
> >        Block IO
> >
> >      000000007eec6140 (efiblk#0:1)
> >        /RamDisk(0x41000000,4974afff,3d5abd30-4175-87ce-6d64-d2ade523c4bb,0x0)/HD(1,0x01,0,0x0,0x33800)
> >        Block IO
> >
> >      000000007eec62b0 (efiblk#0:2)
> >        /RamDisk(0x41000000,4974afff,3d5abd30-4175-87ce-6d64-d2ade523c4bb,0x0)/HD(2,0x01,0,0x33800,0x10000)
> >        Block IO
> >        System Partition
> >        Simple File System
> >
> >    => dm tree
> >
> >      blk           0  [ + ]   efi_blk               `-- efiblk#0
> >      partition     0  [ + ]   blk_partition             |-- efiblk#0:1
> >      partition     1  [ + ]   blk_partition             `-- efiblk#0:2
> >
> > Debian can be successfully installed with this RAM disk on QEMU.
> >
> > [TODO]
> > - udevices created in ./lib/efi_driver/efi_block_device.c::efi_bl_bind()
> >    are not removed when the efi_handle is removed.
> >    So after unload the RAM disk, udevices still exist.
> >    I plan to add a udevice removal process in ./lib/efi_driver/efi_uclass.c::efi_uc_stop().
> >    In addition, I also plan to add unbind() callback in struct efi_driver_ops.
> >
> >
> > [1] https://deb.debian.org/debian/dists/bookworm/main/installer-arm64/current/images/netboot/mini.iso
> >
> > Masahisa Kojima (4):
> >    efi_loader: add RAM disk device path
> >    efi_loader: add EFI_RAM_DISK_PROTOCOL implementation
> >    cmd: efidebug: add RAM disk mount command
> >    efi_selftest: add EFI_RAM_DISK_PROTOCOL selftest
> >
> >   cmd/efidebug.c                           | 117 ++++++
> >   include/efi_api.h                        |  32 ++
> >   include/efi_loader.h                     |   4 +
> >   lib/efi_driver/efi_uclass.c              |   7 +-
> >   lib/efi_loader/Kconfig                   |   6 +
> >   lib/efi_loader/Makefile                  |   1 +
> >   lib/efi_loader/efi_device_path_to_text.c |  14 +
> >   lib/efi_loader/efi_ram_disk.c            | 334 +++++++++++++++
> >   lib/efi_loader/efi_setup.c               |   6 +
> >   lib/efi_selftest/Makefile                |   1 +
> >   lib/efi_selftest/efi_selftest_ram_disk.c | 511 +++++++++++++++++++++++
> >   lib/uuid.c                               |   4 +
> >   12 files changed, 1035 insertions(+), 2 deletions(-)
> >   create mode 100644 lib/efi_loader/efi_ram_disk.c
> >   create mode 100644 lib/efi_selftest/efi_selftest_ram_disk.c
> >
> >
> > base-commit: e2e2aea5733f0d23cd9593bbefe5c803c552dcb9
>