[PATCH 0/4] introduce EFI_RAM_DISK_PROTOCOL

[Heinrich Schuchardt]

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.

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.

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.

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