xen/smp: Warn user why they keel over - nosmp or noapic and what to use instead.

commit ed467e69f16e6b480e2face7bc5963834d025f91 upstream.

We have hit a couple of customer bugs where they would like to
use those parameters to run an UP kernel - but both of those
options turn of important sources of interrupt information so
we end up not being able to boot. The correct way is to
pass in 'dom0_max_vcpus=1' on the Xen hypervisor line and
the kernel will patch itself to be a UP kernel.

Fixes bug: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=637308

Acked-by: Ian Campbell <Ian.Campbell@eu.citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index d2dfbf500fc8e9b2d6167b7ccd861f6e0a653c6f..9aac865f9bde1a822870bf828b5049f05a725f86 100644 (file)
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -31,6 +31,7 @@
 #include <xen/page.h>
 #include <xen/events.h>
 
+#include <xen/hvc-console.h>
 #include "xen-ops.h"
 #include "mmu.h"
 
@@ -181,6 +182,15 @@ static void __init xen_smp_prepare_cpus(unsigned int max_cpus)
 {
        unsigned cpu;
 
+       if (skip_ioapic_setup) {
+               char *m = (max_cpus == 0) ?
+                       "The nosmp parameter is incompatible with Xen; " \
+                       "use Xen dom0_max_vcpus=1 parameter" :
+                       "The noapic parameter is incompatible with Xen";
+
+               xen_raw_printk(m);
+               panic(m);
+       }
        xen_init_lock_cpu(0);
 
        smp_store_cpu_info(0);