Re: [Xen-devel] spawn second serial console/port

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 11 Nov 2010, Vasiliy G Tolstov wrote:
> I need second serial port (hvc1) how can i spawn it to connect from dom0
> to domU ?
> 
> Can it possible without modification of xen sources? Odes it possible to
> write something in config file of domU?
> 
> If it not possible to do without modification of source code, can You
> take me some info, what file/files i need to review?
> 

it is possible and most of the code is out there somewhere but it won't
work out of the box.

First you need yo checkout this branch:

git://xenbits.xen.org/people/sstabellini/linux-pvhvm.git 2.6.35-rc5-pvhvm-v7

give a look at 8d380069c8a00f89acb43f7c7b3a7fc4357a5cac and
0d5aa905d52d960ca25f5adccec7fda9fd7e8a78, they implement PV multiconsole
support in the kernel (these commits are not upstream yet).

Then you need to edit xl to add a second PV console (it is not possible
to do that from the VM config file), a quick hack like this should work:


diff -r 388c44a63613 tools/libxl/xl_cmdimpl.c
--- a/tools/libxl/xl_cmdimpl.c  Wed Nov 10 14:56:06 2010 +0000
+++ b/tools/libxl/xl_cmdimpl.c  Fri Nov 12 13:17:24 2010 +0000
@@ -1686,13 +1686,17 @@ start:
 
         init_console_info(&console, 0, &state);
         console.domid = domid;
-        if (d_config.num_vfbs)
-             console.consback = LIBXL_CONSBACK_IOEMU;
+        console.consback = LIBXL_CONSBACK_IOEMU;
         libxl_device_console_add(&ctx, domid, &console);
         libxl_device_console_destroy(&console);
 
-        if (d_config.num_vfbs)
-            libxl_create_xenpv_qemu(&ctx, domid, d_config.vfbs, &dm_starting);
+        init_console_info(&console, 1, NULL);
+        console.domid = domid;
+        console.consback = LIBXL_CONSBACK_IOEMU;
+        libxl_device_console_add(&ctx, domid, &console);
+        libxl_device_console_destroy(&console);
+
+        libxl_create_xenpv_qemu(&ctx, domid, d_config.vfbs, &dm_starting);
     }
 
     if (dm_starting)


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