[Xen-devel] [PATCH 5/5] x86: place non-parked CPUs into wait-for-SIPI state after offlining

["Jan Beulich" <JBeulich@xxxxxxxx>]

This is presumably more power efficient than keeping them in a HLT loop,
and I supposed also the state in which they're being handed off by
firmware.

Split off from wakeup_secondary_cpu() the code to assert/deassert INIT
(and in turn also recurring wait-for-send-completion code), and re-use
it from __cpu_die(). Take the opportunity and add the previously
missing apic_wait_icr_idle() at the start of the sequence.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -415,10 +415,25 @@ void start_secondary(void *unused)
 
 extern void *stack_start;
 
-static int wakeup_secondary_cpu(int phys_apicid, unsigned long start_eip)
+static unsigned int wait_send(void)
 {
-    unsigned long send_status = 0, accept_status = 0;
-    int maxlvt, timeout, i;
+    unsigned int send_status, timeout = 0;
+
+    Dprintk("Waiting for send to finish...\n");
+    do {
+        Dprintk("+");
+        udelay(100);
+        send_status = apic_read(APIC_ICR) & APIC_ICR_BUSY;
+    } while ( send_status && (timeout++ < 1000) );
+
+    return send_status;
+}
+
+static unsigned int init_secondary_cpu(unsigned int phys_apicid)
+{
+    unsigned int send_status = 0;
+
+    apic_wait_icr_idle();
 
     /*
      * Be paranoid about clearing APIC errors.
@@ -436,13 +451,7 @@ static int wakeup_secondary_cpu(int phys
 
     if ( !x2apic_enabled )
     {
-        Dprintk("Waiting for send to finish...\n");
-        timeout = 0;
-        do {
-            Dprintk("+");
-            udelay(100);
-            send_status = apic_read(APIC_ICR) & APIC_ICR_BUSY;
-        } while ( send_status && (timeout++ < 1000) );
+        send_status = wait_send();
 
         mdelay(10);
 
@@ -450,13 +459,7 @@ static int wakeup_secondary_cpu(int phys
 
         apic_icr_write(APIC_INT_LEVELTRIG | APIC_DM_INIT, phys_apicid);
 
-        Dprintk("Waiting for send to finish...\n");
-        timeout = 0;
-        do {
-            Dprintk("+");
-            udelay(100);
-            send_status = apic_read(APIC_ICR) & APIC_ICR_BUSY;
-        } while ( send_status && (timeout++ < 1000) );
+        send_status = wait_send();
     }
     else if ( tboot_in_measured_env() )
     {
@@ -471,7 +474,16 @@ static int wakeup_secondary_cpu(int phys
         udelay(10);
     }
 
-    maxlvt = get_maxlvt();
+    return send_status;
+}
+
+static unsigned int wakeup_secondary_cpu(unsigned int phys_apicid,
+                                         unsigned int start_eip)
+{
+    unsigned int send_status, accept_status = 0;
+    unsigned int maxlvt = get_maxlvt(), i;
+
+    send_status = init_secondary_cpu(phys_apicid);
 
     for ( i = 0; i < 2; i++ )
     {
@@ -491,15 +503,9 @@ static int wakeup_secondary_cpu(int phys
             /* Give the other CPU some time to accept the IPI. */
             udelay(300);
 
-            Dprintk("Startup point 1.\n");
+            Dprintk("Startup point %u.\n", i + 1);
 
-            Dprintk("Waiting for send to finish...\n");
-            timeout = 0;
-            do {
-                Dprintk("+");
-                udelay(100);
-                send_status = apic_read(APIC_ICR) & APIC_ICR_BUSY;
-            } while ( send_status && (timeout++ < 1000) );
+            send_status = wait_send();
 
             /* Give the other CPU some time to accept the IPI. */
             udelay(200);
@@ -519,7 +525,7 @@ static int wakeup_secondary_cpu(int phys
     if ( send_status )
         printk("APIC never delivered???\n");
     if ( accept_status )
-        printk("APIC delivery error (%lx).\n", accept_status);
+        printk("APIC delivery error (%x).\n", accept_status);
 
     return (send_status | accept_status);
 }
@@ -1238,6 +1244,9 @@ void __cpu_die(unsigned int cpu)
         if ( (++i % 10) == 0 )
             printk(KERN_ERR "CPU %u still not dead...\n", cpu);
     }
+
+    if ( !park_offline_cpus )
+        init_secondary_cpu(x86_cpu_to_apicid[cpu]);
 }
 
 int cpu_add(uint32_t apic_id, uint32_t acpi_id, uint32_t pxm)




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