Xen devel - Apr 2009 - Passthrough of Serial port /dev/ttyS0 to PV and HVM domains problems

I''m trying to get the following working:

Serial port (/dev/ttyS0) passthrough to a PV or HVM domain, together with
xenfb and usb passthrough.

passthrough of the serial port works fine in a PV without xenfb (and so
without qemu) by using the following lines in the config:

        irq = [4]
        ioports = ["3f8-3ff"]

by using
        vfb = [ ''vnc=1,vnclisten=0.0.0.0,vncunused=1'' ]
it will use qemu, so the lines above don''t work anymore.

Now it uses qemu which is the same for HVM and PVM


using   serial=''/dev/ttyS0'' in the config files
doesn''t work, although it should according to
the qemu manpages.
using:
    echo "test" > /dev/ttyS0
on the host,and
    cat /dev/ttyS0
on the guest, to test it, it shows nothing on the guest





when using serial=pty in the config file, and using
using:
    echo "test" > /dev/pts/0
on the host,and
    cat /dev/ttyS0
on the guest, to test it, it shows the test string on the guest


using:
socat /dev/ttyS0 /dev/pts/0 works passing through the hardware serial port
to the guest, but it''s not very elegant since the pts/0 could change.






Questions:
- Shouldn''t the serial=''/dev/ttyS0'' config option
work in the first place
for the qemu domains (PV or HVM) ?

- is xenfb and thus x11 support indeed only available on PV''s using
qemu ?

- is there any other way to get sdl/vnc graphics in a domU together with
serial port passthrough, without using external tools as socat ?

- wouldn''t it be nice to have some sort of standardization in all the
available passthrough options, or at least an overview in Dom0 of what is
passthrouged to what in the different guest domains.
There are quite a few variables at the moment:
          -xend-PV or qemu-PV/HVM.
          -PCI or USB or serial or parport passthrough.
          -with or without VT-D/iommu support.
And it is difficult to find out the status (working/partially/not-working)
of all these options it leads to. It also means there is not much
documentation around.


I hope anyone can help ...


Regards,

Sander Eikelenboom






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In upstream qemu my issue was fixed, see
http://git.kernel.dk/?p=qemu.git;a=commit;h=b4abdfa4fbf4afaa7540ddaf814236e7844935ff
also send a patch with this post.
Passthrough of the hardware serial port to qemu works like a charm with my
serial
touchscreen to a xen HVM with linux or windows.

Is it already possible to use upstream qemu instead of qemu-dm with xen, or is
it still
depending on modifications in it''s own qemu-dm ?

--
          Sander Eikelenboom




--- qemu-char.c 2009-04-09 15:00:09.000000000 +0200
+++ qemu-char.c 2009-04-09 15:09:14.000000000 +0200
@@ -1055,37 +1055,48 @@ static int tty_serial_ioctl(CharDriverSt
         }
         break;
     case CHR_IOCTL_SERIAL_GET_TIOCM:
         {
             int sarg = 0;
             int *targ = (int *)arg;
             ioctl(s->fd_in, TIOCMGET, &sarg);
             *targ = 0;
-            if (sarg | TIOCM_CTS)
+            if (sarg & TIOCM_CTS)
                 *targ |= CHR_TIOCM_CTS;
-            if (sarg | TIOCM_CAR)
+            if (sarg & TIOCM_CAR)
                 *targ |= CHR_TIOCM_CAR;
-            if (sarg | TIOCM_DSR)
+            if (sarg & TIOCM_DSR)
                 *targ |= CHR_TIOCM_DSR;
-            if (sarg | TIOCM_RI)
+            if (sarg & TIOCM_RI)
                 *targ |= CHR_TIOCM_RI;
-            if (sarg | TIOCM_DTR)
+            if (sarg & TIOCM_DTR)
                 *targ |= CHR_TIOCM_DTR;
-            if (sarg | TIOCM_RTS)
+            if (sarg & TIOCM_RTS)
                 *targ |= CHR_TIOCM_RTS;
         }
         break;
     case CHR_IOCTL_SERIAL_SET_TIOCM:
         {
             int sarg = *(int *)arg;
             int targ = 0;
-            if (sarg | CHR_TIOCM_DTR)
+            ioctl(s->fd_in, TIOCMGET, &targ);
+            targ &= ~(CHR_TIOCM_CTS | CHR_TIOCM_CAR | CHR_TIOCM_DSR
+                    | CHR_TIOCM_RI | CHR_TIOCM_DTR | CHR_TIOCM_RTS);
+            if (sarg & CHR_TIOCM_CTS)
+                targ |= TIOCM_CTS;
+            if (sarg & CHR_TIOCM_CAR)
+                targ |= TIOCM_CAR;
+            if (sarg & CHR_TIOCM_DSR)
+                targ |= TIOCM_DSR;
+            if (sarg & CHR_TIOCM_RI)
+                targ |= TIOCM_RI;
+            if (sarg & CHR_TIOCM_DTR)
                 targ |= TIOCM_DTR;
-            if (sarg | CHR_TIOCM_RTS)
+            if (sarg & CHR_TIOCM_RTS)
                 targ |= TIOCM_RTS;
             ioctl(s->fd_in, TIOCMSET, &targ);
         }
         break;
     default:
         return -ENOTSUP;
     }
     return 0;



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Sander Eikelenboom writes ("[Xen-devel] [Patch] fix Passthrough of Serial
port to tty for qemu-dm (from qemu-upstream)"):
> In upstream qemu my issue was fixed, see
http://git.kernel.dk/?p=qemu.git;a=commit;h=b4abdfa4fbf4afaa7540ddaf814236e7844935ff
Thanks.

I''ll look into pulling from the most recent qemu stable branch - which
appears to contain this fix.

Ian.

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