y86/vmx: dump PIR and vIRR before ASSERT()

Commit c7bdecae42 ("x86/apicv: fix RTC periodic timer and apicv issue") has
added a assertion that intack.vector is the highest priority vector. But
according to the osstest, the assertion failed sometimes. More discussion can
be found in the thread
(https://lists.xenproject.org/archives/html/xen-devel/2017-01/msg01019.html).

The assertion failure is hard to reproduce. In order to root cause issue, this
patch is to add logs to dump PIR and vIRR when failure takes place. It should
be reverted once the root cause is found.

Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>

xen/arch/x86/hvm/vmx/intr.c

@@ -23,6 +23,7 @@
 #include <xen/errno.h>
 #include <xen/trace.h>
 #include <xen/event.h>
+#include <asm/apicdef.h>
 #include <asm/current.h>
 #include <asm/cpufeature.h>
 #include <asm/processor.h>
@@ -318,6 +319,45 @@ void vmx_intr_assist(void)
         */
         if ( pt_vector != -1 )
         {
+            /*
+             * We assert that intack.vector is the highest priority vector for
+             * only an interrupt from vlapic can reach this point and the
+             * highest vector is chosen in hvm_vcpu_has_pending_irq().
+             * But, in fact, the assertion failed sometimes. It is suspected
+             * that PIR is not synced to vIRR which makes pt_vector is left in
+             * PIR. In order to verify this suspicion, dump some information
+             * when the assertion fails.
+             */
+            if ( unlikely(intack.vector < pt_vector) )
+            {
+                const struct vlapic *vlapic;
+                const struct pi_desc *pi_desc;
+                const uint32_t *word;
+                unsigned int i;
+
+                printk(XENLOG_ERR "%pv: intack: %02x:%u pt: %02x\n",
+                       current, intack.source, intack.vector, pt_vector);
+
+                vlapic = vcpu_vlapic(v);
+                if ( vlapic && vlapic->regs->data )
+                {
+                    word = (const void *)&vlapic->regs->data[APIC_IRR];
+                    printk(XENLOG_ERR "vIRR:");
+                    for ( i = NR_VECTORS / 32; i-- ; )
+                        printk(" %08x", word[i*4]);
+                    printk("\n");
+                }
+
+                pi_desc = &v->arch.hvm_vmx.pi_desc;
+                if ( pi_desc && pi_desc->pir )
+                {
+                    word = (const void *)&pi_desc->pir;
+                    printk(XENLOG_ERR " PIR:");
+                    for ( i = NR_VECTORS / 32; i-- ; )
+                        printk(" %08x", word[i]);
+                    printk("\n");
+                }
+            }
             ASSERT(intack.vector >= pt_vector);
             vmx_set_eoi_exit_bitmap(v, intack.vector);
         }