QEMU + Ventoy USB: UEFI boot always drops to EFI Shell instead of auto-boot

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Post (English – faithful translation)
Hello,
I am trying to boot a Ventoy USB drive in UEFI mode using QEMU with OVMF, but QEMU always drops into the EFI Shell instead of automatically booting Ventoy.
What works

• The Ventoy USB boots correctly on real hardware in UEFI mode
  
• The Ventoy USB boots correctly in QEMU using Legacy/BIOS mode
  
• From the EFI Shell, manual boot works:
  
  fsX:cd EFI\BOOTBOOTX64.EFI
  
• After running this, Ventoy starts normally.
  

What does NOT work

• Automatic UEFI boot when using QEMU
  
• Even when using:
  • startup.nsh
    
  • placed in the root of the USB
    
  • Clean or regenerated OVMF VARS files
    
  • Passing the USB drive directly as a raw block device
    QEMU still always boots into the EFI Shell.
    

Environment

• Host OS: Linux
  
• QEMU:
  qemu-system-x86_64
  
• UEFI firmware:
  OVMF_CODE_4M.fd
  
• +
  OVMF_VARS_4M.fd
  
• USB drive passed as a raw block device
  
• Standard Ventoy layout (GPT with EFI partition)
  

Minimal QEMU command (manual boot only works)

Code:

sudo qemu-system-x86_64 \
  -m 2048 \
  -drive if=pflash,format=raw,readonly=on,file=/usr/share/OVMF/OVMF_CODE_4M.fd \
  -drive if=pflash,format=raw,file=/usr/share/OVMF/OVMF_VARS_4M.fd \
  -drive file=/dev/sdX,format=raw

Question
Is this a known limitation or incompatibility between:

• QEMU + OVMF
  
• and Ventoy UEFI boot from a USB device?
  

Are there:

• recommended QEMU settings for Ventoy UEFI boot?
  
• known workarounds (other than manual EFI Shell boot)?
  
• an explanation of why OVMF does not automatically detect
  BOOTX64.EFI
  
• on the Ventoy USB?
  

Thanks in advance for any clarification.

Written and then translated with the help of chatGPT