[Xen-devel] [PATCH v5 1/4] VT-d PI: track the number of vcpus on pi blocking list

[Chao Gao <chao.gao@xxxxxxxxx>]

This patch adds a field, counter, in struct vmx_pi_blocking_vcpu to track
how many entries are on the pi blocking list.

Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
---
v5:
 - introduce two functions for adding or removing vcpus from pi blocking list.
 - check the sanity of vcpu count on pi blocking list
v4:
 - non-trace part of Patch 1 in v3

---
 xen/arch/x86/hvm/vmx/vmx.c | 42 ++++++++++++++++++++++++++++++++----------
 1 file changed, 32 insertions(+), 10 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 67fc85b..bf17988 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -83,6 +83,7 @@ static int vmx_vmfunc_intercept(struct cpu_user_regs *regs);
 struct vmx_pi_blocking_vcpu {
     struct list_head     list;
     spinlock_t           lock;
+    unsigned int         counter;
 };
 
 /*
@@ -100,6 +101,24 @@ void vmx_pi_per_cpu_init(unsigned int cpu)
     spin_lock_init(&per_cpu(vmx_pi_blocking, cpu).lock);
 }
 
+static void vmx_pi_add_vcpu(struct pi_blocking_vcpu *pbv,
+                            struct vmx_pi_blocking_vcpu *vpbv)
+{
+    ASSERT(spin_is_locked(&vpbv->lock));
+    add_sized(&vpbv->counter, 1);
+    ASSERT(read_atomic(&vpbv->counter));
+    list_add_tail(&pbv->list, &vpbv->list);
+}
+
+static void vmx_pi_del_vcpu(struct pi_blocking_vcpu *pbv,
+                            struct vmx_pi_blocking_vcpu *vpbv)
+{
+    ASSERT(spin_is_locked(&vpbv->lock));
+    ASSERT(read_atomic(&vpbv->counter));
+    list_del(&pbv->list);
+    add_sized(&vpbv->counter, -1);
+}
+
 static void vmx_vcpu_block(struct vcpu *v)
 {
     unsigned long flags;
@@ -120,8 +139,8 @@ static void vmx_vcpu_block(struct vcpu *v)
      */
     ASSERT(old_lock == NULL);
 
-    list_add_tail(&v->arch.hvm_vmx.pi_blocking.list,
-                  &per_cpu(vmx_pi_blocking, v->processor).list);
+    vmx_pi_add_vcpu(&v->arch.hvm_vmx.pi_blocking,
+                    &per_cpu(vmx_pi_blocking, v->processor));
     spin_unlock_irqrestore(pi_blocking_list_lock, flags);
 
     ASSERT(!pi_test_sn(pi_desc));
@@ -186,7 +205,9 @@ static void vmx_pi_unblock_vcpu(struct vcpu *v)
     if ( v->arch.hvm_vmx.pi_blocking.lock != NULL )
     {
         ASSERT(v->arch.hvm_vmx.pi_blocking.lock == pi_blocking_list_lock);
-        list_del(&v->arch.hvm_vmx.pi_blocking.list);
+        vmx_pi_del_vcpu(&v->arch.hvm_vmx.pi_blocking,
+                        container_of(pi_blocking_list_lock,
+                                     struct vmx_pi_blocking_vcpu, lock));
         v->arch.hvm_vmx.pi_blocking.lock = NULL;
     }
 
@@ -234,7 +255,7 @@ void vmx_pi_desc_fixup(unsigned int cpu)
          */
         if ( pi_test_on(&vmx->pi_desc) )
         {
-            list_del(&vmx->pi_blocking.list);
+            vmx_pi_del_vcpu(&vmx->pi_blocking, &per_cpu(vmx_pi_blocking, cpu));
             vmx->pi_blocking.lock = NULL;
             vcpu_unblock(container_of(vmx, struct vcpu, arch.hvm_vmx));
         }
@@ -257,8 +278,9 @@ void vmx_pi_desc_fixup(unsigned int cpu)
             write_atomic(&vmx->pi_desc.ndst,
                          x2apic_enabled ? dest : MASK_INSR(dest, 
PI_xAPIC_NDST_MASK));
 
-            list_move(&vmx->pi_blocking.list,
-                      &per_cpu(vmx_pi_blocking, new_cpu).list);
+            vmx_pi_del_vcpu(&vmx->pi_blocking, &per_cpu(vmx_pi_blocking, cpu));
+            vmx_pi_add_vcpu(&vmx->pi_blocking, &per_cpu(vmx_pi_blocking,
+                                                        new_cpu));
             vmx->pi_blocking.lock = new_lock;
 
             spin_unlock(new_lock);
@@ -2351,9 +2373,9 @@ static struct hvm_function_table __initdata 
vmx_function_table = {
 static void pi_wakeup_interrupt(struct cpu_user_regs *regs)
 {
     struct arch_vmx_struct *vmx, *tmp;
-    spinlock_t *lock = &per_cpu(vmx_pi_blocking, smp_processor_id()).lock;
-    struct list_head *blocked_vcpus =
-               &per_cpu(vmx_pi_blocking, smp_processor_id()).list;
+    unsigned int cpu = smp_processor_id();
+    spinlock_t *lock = &per_cpu(vmx_pi_blocking, cpu).lock;
+    struct list_head *blocked_vcpus = &per_cpu(vmx_pi_blocking, cpu).list;
 
     ack_APIC_irq();
     this_cpu(irq_count)++;
@@ -2369,7 +2391,7 @@ static void pi_wakeup_interrupt(struct cpu_user_regs 
*regs)
     {
         if ( pi_test_on(&vmx->pi_desc) )
         {
-            list_del(&vmx->pi_blocking.list);
+            vmx_pi_del_vcpu(&vmx->pi_blocking, &per_cpu(vmx_pi_blocking, cpu));
             ASSERT(vmx->pi_blocking.lock == lock);
             vmx->pi_blocking.lock = NULL;
             vcpu_unblock(container_of(vmx, struct vcpu, arch.hvm_vmx));
-- 
1.8.3.1


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