[xen staging] x86/smpboot: Allow making an INIT IPI conditional

[patchbot@xxxxxxx]

commit f31029cc73d94dcfdf02c879176e8105d37643da
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Mon Jan 11 15:54:38 2021 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Fri Jan 29 11:59:54 2021 +0000

    x86/smpboot: Allow making an INIT IPI conditional
    
    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>
    Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 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 f5aba3c555..61ce923189 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();
--
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