Bug#637308: xen-linux-system-2.6.32-5-xen-amd64: with kernel option 'nosmp', dom0 hangup while init PCI-Express Fusion-MPT SAS
On Tue, Aug 30, 2011 at 09:04:30AM +0100, Ian Campbell wrote:
> On Mon, 2011-08-29 at 12:55 +0100, Ben Hutchings wrote:
> > On Mon, 2011-08-29 at 10:07 +0400, Константин Алексеев wrote:
> > > I think this bug may be closed.
> > > I posted it to xen devel list and get answer:
> > > "It's really an unsupported configuration. If you want to limit dom0 vcpus
> > > then dom0_max_vcpus= on Xen command line is the correct way."
> > >
> > > http://lists.xensource.com/archives/html/xen-devel/2011-08/msg00665.html
> >
> > Maybe we should panic in this case?
>
> It's a bit sad but yes I think that would be better than leaving traps
> for the unwary given that the issue is unlikely to bubble up most Xen
> developers' todo list any time soon
>
> Your use of skip_ioapic_setup clued me into the probable difference
> between nosmp and dom0_max_vcpus=1 -- the disabling of IOAPIC most
> likely matters to Xen. Konrad does that sound right?
Yes.
>
> > Something like this (untested):
>
> Looks plausible to me.
>
> >
> > diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
> > index e79dbb9..2671b96 100644
> > --- a/arch/x86/xen/smp.c
> > +++ b/arch/x86/xen/smp.c
> > @@ -21,6 +21,7 @@
> > #include <asm/desc.h>
> > #include <asm/pgtable.h>
> > #include <asm/cpu.h>
> > +#include <asm/io_apic.h>
> >
> > #include <xen/interface/xen.h>
> > #include <xen/interface/vcpu.h>
> > @@ -207,6 +208,12 @@ static void __init xen_smp_prepare_cpus(unsigned int max_cpus)
> > unsigned cpu;
> > unsigned int i;
> >
> > + if (skip_ioapic_setup)
> > + panic((max_cpus == 0) ?
> > + "The nosmp parameter is incompatible with Xen; "
> > + "use Xen dom0_max_vcpus=1 parameter" :
> > + "The noapic parameter is incompatible with Xen");
> > +
It might make sense to also use 'xen_raw_printk' as sometimes you don't
get to see the panic - you end up with this unhelpfull message:
(XEN) domain_crash_sync called from entry.S
(XEN) Domain 0 (vcpu#0) crashed on cpu#0:
.. snip..
so something like this:
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index b4533a8..8424dd4 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -32,6 +32,7 @@
#include <xen/page.h>
#include <xen/events.h>
+#include <xen/hvc-console.h>
#include "xen-ops.h"
#include "mmu.h"
@@ -207,6 +208,15 @@ static void __init xen_smp_prepare_cpus(unsigned int max_cpus)
unsigned cpu;
unsigned int i;
+ 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);
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