xen: SMP guest support

This is a fairly straightforward Xen implementation of smp_ops.

Xen has its own IPI mechanisms, and has no dependency on any
APIC-based IPI.  The smp_ops hooks and the flush_tlb_others pv_op
allow a Xen guest to avoid all APIC code in arch/i386 (the only apic
operation is a single apic_read for the apic version number).

One subtle point which needs to be addressed is unpinning pagetables
when another cpu may have a lazy tlb reference to the pagetable. Xen
will not allow an in-use pagetable to be unpinned, so we must find any
other cpus with a reference to the pagetable and get them to shoot
down their references.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Andi Kleen <ak@suse.de>

1 files changed, 5 insertions, 0 deletions

diff --git a/arch/i386/xen/setup.c b/arch/i386/xen/setup.c
index 7da93ee612f6..18a994d5a4c5 100644
--- a/arch/i386/xen/setup.c
+++ b/arch/i386/xen/setup.c
@@ -94,4 +94,9 @@ void __init xen_arch_setup(void)
                COMMAND_LINE_SIZE : MAX_GUEST_CMDLINE);
 
         pm_idle = xen_idle;
+
+#ifdef CONFIG_SMP
+        /* fill cpus_possible with all available cpus */
+        xen_fill_possible_map();
+#endif
 }