x86: vMSI: Fix msi irq affinity issue for hvm guest.

There is a race between guest setting new vector and doing EOI on old
vector.  Once guest sets new vector before its doing EOI on vector,
when guest does eoi, hypervisor may fail to find the related pirq, and
hypervisor may miss to EOI real vector and leads to system hang.  We
may need to add a timer for each pirq interrupt source to avoid host
hang, but this is another topic, and will be addressed later.

Signed-off-by: Xiantao Zhang <xiantao.zhang@intel.com>

xen/arch/x86/hvm/vmsi.c

@@ -92,8 +92,11 @@ int vmsi_deliver(struct domain *d, int pirq)
     case dest_LowestPrio:
     {
         target = vlapic_lowest_prio(d, NULL, 0, dest, dest_mode);
-        if ( target != NULL )
+        if ( target != NULL ) {
             vmsi_inj_irq(d, target, vector, trig_mode, delivery_mode);
+            hvm_irq_dpci->mirq[pirq].gmsi.old_gvec =
+                                    hvm_irq_dpci->mirq[pirq].gmsi.gvec;
+        }
         else
             HVM_DBG_LOG(DBG_LEVEL_IOAPIC, "null round robin: "
                         "vector=%x delivery_mode=%x\n",
@@ -106,9 +109,12 @@ int vmsi_deliver(struct domain *d, int pirq)
     {
         for_each_vcpu ( d, v )
             if ( vlapic_match_dest(vcpu_vlapic(v), NULL,
-                                   0, dest, dest_mode) )
+                                   0, dest, dest_mode) ) {
                 vmsi_inj_irq(d, vcpu_vlapic(v),
                              vector, trig_mode, delivery_mode);
+                hvm_irq_dpci->mirq[pirq].gmsi.old_gvec =
+                                    hvm_irq_dpci->mirq[pirq].gmsi.gvec;
+            }
         break;
     }
 

xen/drivers/passthrough/io.c

@@ -164,7 +164,9 @@ int pt_irq_create_bind_vtd(
         {
             hvm_irq_dpci->mirq[pirq].flags = HVM_IRQ_DPCI_MACH_MSI |
                                              HVM_IRQ_DPCI_GUEST_MSI;
+            hvm_irq_dpci->mirq[pirq].gmsi.old_gvec = pt_irq_bind->u.msi.gvec;
             hvm_irq_dpci->mirq[pirq].gmsi.gvec = pt_irq_bind->u.msi.gvec;
+            hvm_irq_dpci->mirq[pirq].gmsi.old_gflags = pt_irq_bind->u.msi.gflags;
             hvm_irq_dpci->mirq[pirq].gmsi.gflags = pt_irq_bind->u.msi.gflags;
             /* bind after hvm_irq_dpci is setup to avoid race with irq handler*/
             rc = pirq_guest_bind(d->vcpu[0], pirq, 0);
@@ -178,6 +180,8 @@ int pt_irq_create_bind_vtd(
             {
                 hvm_irq_dpci->mirq[pirq].gmsi.gflags = 0;
                 hvm_irq_dpci->mirq[pirq].gmsi.gvec = 0;
+                hvm_irq_dpci->mirq[pirq].gmsi.old_gvec = 0;
+                hvm_irq_dpci->mirq[pirq].gmsi.old_gflags = 0;
                 hvm_irq_dpci->mirq[pirq].flags = 0;
                 clear_bit(pirq, hvm_irq_dpci->mapping);
                 spin_unlock(&d->event_lock);
@@ -195,8 +199,14 @@ int pt_irq_create_bind_vtd(
             }
  
             /* if pirq is already mapped as vmsi, update the guest data/addr */
-            hvm_irq_dpci->mirq[pirq].gmsi.gvec = pt_irq_bind->u.msi.gvec;
-            hvm_irq_dpci->mirq[pirq].gmsi.gflags = pt_irq_bind->u.msi.gflags;
+            if ( hvm_irq_dpci->mirq[pirq].gmsi.gvec != pt_irq_bind->u.msi.gvec ) {
+                hvm_irq_dpci->mirq[pirq].gmsi.old_gvec =
+                                    hvm_irq_dpci->mirq[pirq].gmsi.gvec;
+                hvm_irq_dpci->mirq[pirq].gmsi.old_gflags =
+                                    hvm_irq_dpci->mirq[pirq].gmsi.gflags;
+                hvm_irq_dpci->mirq[pirq].gmsi.gvec = pt_irq_bind->u.msi.gvec;
+                hvm_irq_dpci->mirq[pirq].gmsi.gflags = pt_irq_bind->u.msi.gflags;
+            }
         }
         /* Caculate dest_vcpu_id for MSI-type pirq migration */
         dest = hvm_irq_dpci->mirq[pirq].gmsi.gflags & VMSI_DEST_ID_MASK;
@@ -424,14 +434,21 @@ void hvm_dpci_msi_eoi(struct domain *d, int vector)
           pirq = find_next_bit(hvm_irq_dpci->mapping, d->nr_pirqs, pirq + 1) )
     {
         if ( (!(hvm_irq_dpci->mirq[pirq].flags & HVM_IRQ_DPCI_MACH_MSI)) ||
-                (hvm_irq_dpci->mirq[pirq].gmsi.gvec != vector) )
+                (hvm_irq_dpci->mirq[pirq].gmsi.gvec != vector &&
+                 hvm_irq_dpci->mirq[pirq].gmsi.old_gvec != vector) )
             continue;
 
-        dest = hvm_irq_dpci->mirq[pirq].gmsi.gflags & VMSI_DEST_ID_MASK;
-        dest_mode = !!(hvm_irq_dpci->mirq[pirq].gmsi.gflags & VMSI_DM_MASK);
+        if ( hvm_irq_dpci->mirq[pirq].gmsi.gvec == vector ) {
+            dest = hvm_irq_dpci->mirq[pirq].gmsi.gflags & VMSI_DEST_ID_MASK;
+            dest_mode = !!(hvm_irq_dpci->mirq[pirq].gmsi.gflags & VMSI_DM_MASK);
+        } else {
+            dest = hvm_irq_dpci->mirq[pirq].gmsi.old_gflags & VMSI_DEST_ID_MASK;
+            dest_mode = !!(hvm_irq_dpci->mirq[pirq].gmsi.old_gflags & VMSI_DM_MASK);
+        }
         if ( vlapic_match_dest(vcpu_vlapic(current), NULL, 0, dest, dest_mode) )
             break;
     }
+
     if ( pirq < d->nr_pirqs )
         __msi_pirq_eoi(d, pirq);
     spin_unlock(&d->event_lock);

xen/include/xen/hvm/irq.h

@@ -58,8 +58,10 @@ struct dev_intx_gsi_link {
 #define GLFAGS_SHIFT_TRG_MODE       15
 
 struct hvm_gmsi_info {
-    uint32_t gvec;
+    uint16_t gvec;
+    uint16_t old_gvec;
     uint32_t gflags;
+    uint32_t old_gflags;
     int dest_vcpu_id; /* -1 :multi-dest, non-negative: dest_vcpu_id */
 };