xen: initialize cpu masks for pv guests in xen_smp_init

Pv guests don't have ACPI and need the cpu masks to be set
correctly as early as possible so we call xen_fill_possible_map from
xen_smp_init.
On the other hand the initial domain supports ACPI so in this case we skip
xen_fill_possible_map and rely on it. However Xen might limit the number
of cpus usable by the domain, so we filter those masks during smp
initialization using the VCPUOP_is_up hypercall.
It is important that the filtering is done before
xen_setup_vcpu_info_placement.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

1 files changed, 22 insertions, 2 deletions

diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 138676781dd4..834dfeb54e31 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -28,6 +28,7 @@
 #include <asm/xen/interface.h>
 #include <asm/xen/hypercall.h>
 
+#include <xen/xen.h>
 #include <xen/page.h>
 #include <xen/events.h>
 
@@ -156,6 +157,25 @@ static void __init xen_fill_possible_map(void)
 {
         int i, rc;
 
+        if (xen_initial_domain())
+                return;
+
+        for (i = 0; i < nr_cpu_ids; i++) {
+                rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
+                if (rc >= 0) {
+                        num_processors++;
+                        set_cpu_possible(i, true);
+                }
+        }
+}
+
+static void __init xen_filter_cpu_maps(void)
+{
+        int i, rc;
+
+        if (!xen_initial_domain())
+                return;
+
         num_processors = 0;
         disabled_cpus = 0;
         for (i = 0; i < nr_cpu_ids; i++) {
@@ -179,6 +199,7 @@ static void __init xen_smp_prepare_boot_cpu(void)
            old memory can be recycled */
         make_lowmem_page_readwrite(xen_initial_gdt);
 
+        xen_filter_cpu_maps();
         xen_setup_vcpu_info_placement();
 }
 
@@ -195,8 +216,6 @@ static void __init xen_smp_prepare_cpus(unsigned int max_cpus)
         if (xen_smp_intr_init(0))
                 BUG();
 
-        xen_fill_possible_map();
-
         if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
                 panic("could not allocate xen_cpu_initialized_map\n");
 
@@ -487,5 +506,6 @@ static const struct smp_ops xen_smp_ops __initdata = {
 void __init xen_smp_init(void)
 {
         smp_ops = xen_smp_ops;
+        xen_fill_possible_map();
         xen_init_spinlocks();
 }