[PATCH 2/3] x86/smpboot: Allow making an INIT IPI conditional

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

A subsequent change is going to introduce SKINIT support, wherein the APs will
be already be in the wait-for-SIPI state, and an INIT must not be sent.

Introduce a send_INIT boolean, so we can control sending an INIT IPI
separately from sending SIPIs.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Marek Kasiewicz <marek.kasiewicz@xxxxxxxxx>
CC: Norbert Kamiński <norbert.kaminski@xxxxxxxxx>
CC: Michal Zygowski <michal.zygowski@xxxxxxxxx>
CC: Piotr Krol <piotr.krol@xxxxxxxx>
CC: Krystian Hebel <krystian.hebel@xxxxxxxxx>
CC: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
CC: Rich Persaud <persaur@xxxxxxxxx>
CC: Christopher Clark <christopher.w.clark@xxxxxxxxx>
---
 xen/arch/x86/smpboot.c | 78 ++++++++++++++++++++++++++------------------------
 1 file changed, 41 insertions(+), 37 deletions(-)

diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 9eca452ce1..195e3681b4 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -424,6 +424,7 @@ static int wakeup_secondary_cpu(int phys_apicid, unsigned 
long start_eip)
 {
     unsigned long send_status = 0, accept_status = 0;
     int maxlvt, timeout, i;
+    bool send_INIT = true;
 
     /*
      * Some versions of tboot might be able to handle the entire wake sequence
@@ -438,49 +439,52 @@ static int wakeup_secondary_cpu(int phys_apicid, unsigned 
long start_eip)
     apic_write(APIC_ESR, 0);
     apic_read(APIC_ESR);
 
-    Dprintk("Asserting INIT.\n");
+    if ( send_INIT )
+    {
+        Dprintk("Asserting INIT.\n");
 
-    /*
-     * Turn INIT on target chip via IPI
-     */
-    apic_icr_write(APIC_INT_LEVELTRIG | APIC_INT_ASSERT | APIC_DM_INIT,
-                   phys_apicid);
+        /*
+         * Turn INIT on target chip via IPI
+         */
+        apic_icr_write(APIC_INT_LEVELTRIG | APIC_INT_ASSERT | APIC_DM_INIT,
+                       phys_apicid);
 
-    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) );
+        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) );
 
-        mdelay(10);
+            mdelay(10);
 
-        Dprintk("Deasserting INIT.\n");
+            Dprintk("Deasserting INIT.\n");
 
-        apic_icr_write(APIC_INT_LEVELTRIG | APIC_DM_INIT, phys_apicid);
+            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) );
-    }
-    else if ( tboot_in_measured_env() )
-    {
-        /*
-         * With tboot AP is actually spinning in a mini-guest before
-         * receiving INIT. Upon receiving INIT ipi, AP need time to VMExit,
-         * update VMCS to tracking SIPIs and VMResume.
-         *
-         * While AP is in root mode handling the INIT the CPU will drop
-         * any SIPIs
-         */
-        udelay(10);
+            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) );
+        }
+        else if ( tboot_in_measured_env() )
+        {
+            /*
+             * With tboot AP is actually spinning in a mini-guest before
+             * receiving INIT. Upon receiving INIT ipi, AP need time to VMExit,
+             * update VMCS to tracking SIPIs and VMResume.
+             *
+             * While AP is in root mode handling the INIT the CPU will drop
+             * any SIPIs
+             */
+            udelay(10);
+        }
     }
 
     maxlvt = get_maxlvt();
-- 
2.11.0