EFI from usb HDD

Heinrich Schuchardt xypron.glpk at gmx.de
Thu Jun 10 11:47:38 CEST 2021

On 6/10/21 10:44 AM, Michal Simek wrote:
> Hi,
> I am playing with booting from USB via EFI. And I see very weird
> behavior. I have burnt image with grub to USB flashdisk and I have
> tested it on 3 zynqmp boards. zcu102, zcu104 and SOM Kria board.
> On zcu102 grub is going to boot menu and everything is working fine as
> expected.
> On zcu104 and SOM Kria I am able to get grub not to menu. When I list
> partitions in grub I see that only SDs are listed:
> grub> ls
> (hd0) (hd0,msdos1) (hd1) (hd1,msdos1)

Hello Michal,

thanks for sharing your observations.

What devices do hd0 and hd1 relate to?

> On zcu102(working board) I also see usb(gpt) partitions and SD.
> grub> ls
> (hd0) (hd0,gpt2) (hd0,gpt1) (hd1) (hd1,msdos1)

GPT and MBR partitioning are independent of the device type.

> On zcu104 I see one more error message
> "PE image measurement failed"

This is related to CONFIG_EFI_TCG2_PROTOCOL=y. Do you have a TPMv2? This
will not stop disk enumeration.

> But I can't see it on SOM.
> U-Boot image is just the same for all boards. I am using generic
> xilinx_zynqmp_virt_defconfig.
> When I compare DT description for USB between zcu102 and zcu104 they are
> the same. SOM doesn't have usb enabled by default (but I enabled it) but
> grub starts which means that communication with USB is fine.
> It is based on my latest patches available here.
> u-boot/custodians/u-boot-microblaze.git (usb-efi-issue branch)
> Also when I list usb I see all partitions just fine.
> ZynqMP> part list usb 0
> Partition Map for USB device 0  --   Partition Type: EFI
> Part    Start LBA       End LBA         Name
>          Attributes
>          Type GUID
>          Partition GUID
>    1     0x00000800      0x001007fe      "Microsoft basic data"
>          attrs:  0x0000000000000000
>          type:   ebd0a0a2-b9e5-4433-87c0-68b6b72699c7
>          type:   data
>          guid:   0e7f8b3d-296b-4720-be9d-c4687d3c4a77
>    2     0x00100800      0x001197fe      "Microsoft basic data"
>          attrs:  0x0000000000000000
>          type:   ebd0a0a2-b9e5-4433-87c0-68b6b72699c7
>          type:   data
>          guid:   8892eddc-231a-4e6e-a5e1-c310f4482fb7
> Do you have any idea why on one system is working fine to get to menu
> and on others there is an issue to get all partitions even u-boot is
> able to see them and can work with them.
> Thanks,
> Michal

Where is the GRUB binary? - If it is in EFI/boot/bootaa64.efi, it could
be that the USB sub-system is simply not initialized yet when the boot
manager is called by distroboot.

For testing partition detection in the UEFI sub-system it is enough to run

     efidebug devices

Until yesterday we had a problem with partition numbers >= 10, cf.

efi_loader: partition numbers are hexadecimal

Block devices are enumerated in efi_disk_register(). Please, try to add
debug output there to elucidate the problem.

Best regards


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