"Reboot guest system" fails if EMS driver is loaded (PC-98 mode)

[maron2000]

Describe the bug A guest system which loads an EMS driver (e.g. EMM386.EXE) doesn't reboot, but returns to initial screen of Dosbox-x.

To Reproduce Steps to reproduce the behavior:

1. Start Dosbox-x dosbox-x.exe -set machine=pc98
2. IMGMOUNT and boot a guest system with a config.sys including an EMS driver. For example,

   FILES=20
   BUFFERS=8
   DEVICE=a:\DOS\HIMEM.SYS
   DEVICE=a:\DOS\EMM386.EXE /UMB
   SHELL=a:\COMMAND.COM a:\ /p /e:512
   DOS=HIGH,UMB

3. Select "Main" -> "Reboot guest system"
4. Reboot procedure of guest OS starts, but terminates and return to the initial screen. (the same screen you see just after Step 1.) No error messages are shown.

Expected behavior The guest OS shall reboot normally.

Environment (please complete the following information):

• Operating system Host: Windows 10 Pro., Guest: NEC MS-DOS 6.2
• DOSBox-X release version: v0.83.13 Windows SDL2 64-bit (Visual Studio)
• Used configuration: Nothing changed. (Possibly all default settings)

Additional context I can reboot guest OS if EMM386.EXE is NOT loaded. Tested with EMM386.EXE and VEM486.EXE 1.31 beta 13, with and w/o UMB settings.

[Wengier]

I could reproduce the said issue. It seems that something related to EMM386 was not reset properly in this case which caused the guest system to restart again.

[maron2000]

@Wengier Thank you for your confirmation. Though it is not critical, it's more convenient if you can reboot without mounting your image again. So I appreciate your help.