x86/smp: check APIC ID on AP bringup

Check that the processor to be woken up APIC ID is addressable in the
current APIC mode.

Note that in practice systems with APIC IDs > 255 should already have
x2APIC enabled by the firmware, and hence this is mostly a safety
belt.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index fa691b6ba0637e4b2c5fb4481a676f94c48681e2..e4398458027d5512a5c6fae0cf1947504c2dc328 100644 (file)
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -1317,6 +1317,14 @@ int __cpu_up(unsigned int cpu)
     if ( (apicid = x86_cpu_to_apicid[cpu]) == BAD_APICID )
         return -ENODEV;
 
+    if ( (!x2apic_enabled && apicid >= APIC_ALL_CPUS) ||
+         (!iommu_intremap && (apicid >> 8)) )
+    {
+        printk("Unsupported: APIC ID %#x in xAPIC mode w/o interrupt remapping\n",
+               apicid);
+        return -EINVAL;
+    }
+
     if ( (ret = do_boot_cpu(apicid, cpu)) != 0 )
         return ret;