xen/vcpu: Handle xen_vcpu_setup() failure in hotplug

[karo-tx-linux.git] / arch / x86 / xen / enlighten.c

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 276cc21619ec057edb8abc7c222f72224d06eb85..0e7ef69e853151207c985d5306927c09d335acdc 100644 (file)
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -106,8 +106,10 @@ int xen_cpuhp_setup(int (*cpu_up_prepare_cb)(unsigned int),
        return rc >= 0 ? 0 : rc;
 }
 
-static void xen_vcpu_setup_restore(int cpu)
+static int xen_vcpu_setup_restore(int cpu)
 {
+       int rc = 0;
+
        /* Any per_cpu(xen_vcpu) is stale, so reset it */
        xen_vcpu_info_reset(cpu);
 
@@ -117,8 +119,10 @@ static void xen_vcpu_setup_restore(int cpu)
         */
        if (xen_pv_domain() ||
            (xen_hvm_domain() && cpu_online(cpu))) {
-               xen_vcpu_setup(cpu);
+               rc = xen_vcpu_setup(cpu);
        }
+
+       return rc;
 }
 
 /*
@@ -128,7 +132,7 @@ static void xen_vcpu_setup_restore(int cpu)
  */
 void xen_vcpu_restore(void)
 {
-       int cpu;
+       int cpu, rc;
 
        for_each_possible_cpu(cpu) {
                bool other_cpu = (cpu != smp_processor_id());
@@ -148,22 +152,25 @@ void xen_vcpu_restore(void)
                if (xen_pv_domain() || xen_feature(XENFEAT_hvm_safe_pvclock))
                        xen_setup_runstate_info(cpu);
 
-               xen_vcpu_setup_restore(cpu);
-
-               if (other_cpu && is_up &&
+               rc = xen_vcpu_setup_restore(cpu);
+               if (rc)
+                       pr_emerg_once("vcpu restore failed for cpu=%d err=%d. "
+                                       "System will hang.\n", cpu, rc);
+               /*
+                * In case xen_vcpu_setup_restore() fails, do not bring up the
+                * VCPU. This helps us avoid the resulting OOPS when the VCPU
+                * accesses pvclock_vcpu_time via xen_vcpu (which is NULL.)
+                * Note that this does not improve the situation much -- now the
+                * VM hangs instead of OOPSing -- with the VCPUs that did not
+                * fail, spinning in stop_machine(), waiting for the failed
+                * VCPUs to come up.
+                */
+               if (other_cpu && is_up && (rc == 0) &&
                    HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL))
                        BUG();
        }
 }
 
-static void clamp_max_cpus(void)
-{
-#ifdef CONFIG_SMP
-       if (setup_max_cpus > MAX_VIRT_CPUS)
-               setup_max_cpus = MAX_VIRT_CPUS;
-#endif
-}
-
 void xen_vcpu_info_reset(int cpu)
 {
        if (xen_vcpu_nr(cpu) < MAX_VIRT_CPUS) {
@@ -175,7 +182,7 @@ void xen_vcpu_info_reset(int cpu)
        }
 }
 
-void xen_vcpu_setup(int cpu)
+int xen_vcpu_setup(int cpu)
 {
        struct vcpu_register_vcpu_info info;
        int err;
@@ -196,7 +203,7 @@ void xen_vcpu_setup(int cpu)
         */
        if (xen_hvm_domain()) {
                if (per_cpu(xen_vcpu, cpu) == &per_cpu(xen_vcpu_info, cpu))
-                       return;
+                       return 0;
        }
 
        if (xen_have_vcpu_info_placement) {
@@ -230,11 +237,10 @@ void xen_vcpu_setup(int cpu)
                }
        }
 
-       if (!xen_have_vcpu_info_placement) {
-               if (cpu >= MAX_VIRT_CPUS)
-                       clamp_max_cpus();
+       if (!xen_have_vcpu_info_placement)
                xen_vcpu_info_reset(cpu);
-       }
+
+       return ((per_cpu(xen_vcpu, cpu) == NULL) ? -ENODEV : 0);
 }
 
 void xen_reboot(int reason)