Re: [Qemu-discuss] QEMU-i386-static question

[Dr. Pedro E. Colla]

Hi Peter,

Thank you very much for your kind and detailed response.

As it's a cross architecture setup chroot operates on a different platform
(ARM host vs. X86 guest) so using binfmt qemu-i386-static is invoked by the
chroot command, therefore when executed qemu has been already executed.
Under that configuration /dev/ttyUSB0 doesn't exists. I might install the
USB Prolific serial port drivers once in X86 but I don't believe that would
make the chrooted environment (under qemu) to share the port with the host,
does it?

Thanks in advance for your thoughts and tips on the subject. 73 de Pedro
LU7DID

On Fri, Sep 13, 2019 at 6:27 AM Peter Maydell <address@hidden>
wrote:

> On Thu, 12 Sep 2019 at 21:28, Dr. Pedro E. Colla <address@hidden> wrote:
> > I'm trying to implement a chroot environment on a Raspberry Pi with the
> > ultimate intention to run Windows applications using wine.
> >
> > To do that first an x86 chroot environment using the subject emulator is
> > used, then once inside a shell of it wine is invoked.
> >
> > The whole thing works surprisingly well despite my initial expectations
> > given the small CPU resources available.
> >
> > However, I do need for the Windows program to access the serial port
> > (/dev/ttyUSB0 at the host environment); the Windows problem is unable to
> > use that port despite different ways to configure it for wine to
> recognize
> > it; but ultimately I found the problem is the x86 debian running under
> qemu
> > isn't seeing it at all.
> >
> > It seems this version of qemu doesn't handle the usual arguments to
> define
> > character devices or usb devices.
>
> QEMU has two modes of operation:
>  (1) system emulation, where we emulate an entire hardware
>  system for the guest, including various devices. In this mode
>  we allow the user to configure how our emulated devices hook
>  up to the host system via the command line arguments you mention
>
>  (2) user-mode emulation, where we emulate just a single guest
>  Linux process, and pass through all the system calls it makes
>  to the host. In this mode there is no need for any kind of
>  command line options to configure devices, because there are
>  no devices to configure.
>
> qemu-i386-static is the user-mode emulator, case (2). If you
> would like binaries you run under it to be able to see
> the host's /dev/ttyUSB0 you need to ensure that that (special)
> file exists in the chroot before you run QEMU. Then the guest
> binary will be able to open it, exactly as a host binary could.
>
> After that, getting it to be visible to Windows programs running
> under Wine is a Wine configuration question.
>
> thanks
> -- PMM
>