Re: I cannot get any message from domU by console / pv_ops domU kernel crashes with xen_create_contiguous_region failed

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Tue, Dec 22, 2009 at 03:07:21PM -0500, Konrad Rzeszutek Wilk wrote:
> > A also can't seem to pass devices through (unless I'm doing it wrong). 
> > When trying to pass my soundcard do the domU, it appears to be 
> > appropriately hidden from dom0 via xen-pciback.hide kernel param 
> > (/var/log/messages says 'pciback 0000:00:1b.0: seizing device') but when I 
> > try to start my domU with iommu=soft and pci=["00:1b.0"] I get a dozen or 
> 
> You are doing it right.
> 
> > so "BUG: scheduling while atomic" messages w/ call traces.  My domU 
> > eventually starts up ok, but lspci returns with no output.
> 
> Hmm, I wonder if this patch is in your tree:
> 
> commit 1aa61698354ca0582b07eb865e0432a13b459f11
> Author: Ian Campbell <ian.campbell@citrix.com>
> Date:   Thu Dec 17 14:08:25 2009 +0000
> 
>     xen: fix hang on suspend.
> 
> and causing this (or maybe the pciback driver is the culprit and
> the above patch exposes a bug?).

Bummer. Can't blame Ian for it :-(

I updated dom0 with that patch and I am not seeing the failure you described.

> 
> Try reverting that patch and seeing what happens. I the meantime let
> me compile a new Dom0 with the above mentioned commit and see if I get
> the failure too.

Instead of that recommendation try enabling debug options. You can do this
the manual way:

diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
index cc3b51b..ae1648a 100644
--- a/drivers/pci/xen-pcifront.c
+++ b/drivers/pci/xen-pcifront.c
@@ -30,7 +30,7 @@
 #define INVALID_GRANT_REF (0)
 #define INVALID_EVTCHN    (-1)
 
-
+#define DEBUG 1
 struct pci_bus_entry {
 	struct list_head list;
 	struct pci_bus *bus;
diff --git a/drivers/xen/blkback/blkback.c b/drivers/xen/blkback/blkback.c
index 815c0c6..a871a2c 100644
--- a/drivers/xen/blkback/blkback.c
+++ b/drivers/xen/blkback/blkback.c
@@ -64,7 +64,7 @@ MODULE_PARM_DESC(reqs, "Number of blkback requests to allocate");
 
 /* Run-time switchable: /sys/module/blkback/parameters/ */
 static unsigned int log_stats = 0;
-static unsigned int debug_lvl = 0;
+static unsigned int debug_lvl = 1;
 module_param(log_stats, int, 0644);
 module_param(debug_lvl, int, 0644);


Or fiddle with the debug_lvl in /sys/ namespace. 

That might shed some light on what is happening. Also do provide the
output of Dom0, DomU and the lspci -vvv in Dom0 please.