1 files changed, 34 insertions, 1 deletions

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index a8f8844b8d32..4f437dedbdf5 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -809,9 +809,40 @@ static void xen_io_delay(void)
 }
 
 #ifdef CONFIG_X86_LOCAL_APIC
+static unsigned long xen_set_apic_id(unsigned int x)
+{
+        WARN_ON(1);
+        return x;
+}
+static unsigned int xen_get_apic_id(unsigned long x)
+{
+        return ((x)>>24) & 0xFFu;
+}
 static u32 xen_apic_read(u32 reg)
 {
-        return 0;
+        struct xen_platform_op op = {
+                .cmd = XENPF_get_cpuinfo,
+                .interface_version = XENPF_INTERFACE_VERSION,
+                .u.pcpu_info.xen_cpuid = 0,
+        };
+        int ret = 0;
+
+        /* Shouldn't need this as APIC is turned off for PV, and we only
+         * get called on the bootup processor. But just in case. */
+        if (!xen_initial_domain() || smp_processor_id())
+                return 0;
+
+        if (reg == APIC_LVR)
+                return 0x10;
+
+        if (reg != APIC_ID)
+                return 0;
+
+        ret = HYPERVISOR_dom0_op(&op);
+        if (ret)
+                return 0;
+
+        return op.u.pcpu_info.apic_id << 24;
 }
 
 static void xen_apic_write(u32 reg, u32 val)
@@ -849,6 +880,8 @@ static void set_xen_basic_apic_ops(void)
         apic->icr_write = xen_apic_icr_write;
         apic->wait_icr_idle = xen_apic_wait_icr_idle;
         apic->safe_wait_icr_idle = xen_safe_apic_wait_icr_idle;
+        apic->set_apic_id = xen_set_apic_id;
+        apic->get_apic_id = xen_get_apic_id;
 }
 
 #endif