[Xen-devel] [PATCH v3 6/6] VMX: Fixup PI descritpor when cpu is offline

[Feng Wu <feng.wu@xxxxxxxxx>]

When cpu is offline, we need to move all the vcpus in its blocking
list to another online cpu, this patch handles it.

Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
---
 xen/arch/x86/hvm/vmx/vmcs.c       |  1 +
 xen/arch/x86/hvm/vmx/vmx.c        | 54 +++++++++++++++++++++++++++++++++++++++
 xen/include/asm-x86/hvm/vmx/vmx.h |  1 +
 3 files changed, 56 insertions(+)

diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index 1bd875a..f554d4c 100644
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -578,6 +578,7 @@ void vmx_cpu_dead(unsigned int cpu)
     vmx_free_vmcs(per_cpu(vmxon_region, cpu));
     per_cpu(vmxon_region, cpu) = 0;
     nvmx_cpu_dead(cpu);
+    vmx_pi_desc_fixup(cpu);
 }
 
 int vmx_cpu_up(void)
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 071c063..5f428b7 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -211,6 +211,60 @@ static void vmx_pi_blocking_cleanup(struct vcpu *v)
     vmx_pi_remove_vcpu_from_blocking_list(v);
 }
 
+void vmx_pi_desc_fixup(int cpu)
+{
+    unsigned int new_cpu, dest;
+    unsigned long flags;
+    struct arch_vmx_struct *vmx, *tmp;
+    spinlock_t *new_lock, *old_lock = &per_cpu(vmx_pi_blocking, cpu).lock;
+    struct list_head *blocked_vcpus = &per_cpu(vmx_pi_blocking, cpu).list;
+
+    if ( !iommu_intpost )
+        return;
+
+    spin_lock_irqsave(old_lock, flags);
+
+    list_for_each_entry_safe(vmx, tmp, blocked_vcpus, pi_blocking.list)
+    {
+        /*
+         * We need to find an online cpu as the NDST of the PI descriptor, it
+         * doesn't matter whether it is within the cpupool of the domain or
+         * not. As long as it is online, the vCPU will be woken up once the
+         * notification event arrives.
+         */
+restart:
+        new_cpu = cpumask_any(&cpu_online_map);
+        new_lock = &per_cpu(vmx_pi_blocking, new_cpu).lock;
+
+        spin_lock(new_lock);
+
+        /*
+         * If the new_cpu is not online, that means it became offline between
+         * we got 'new_cpu' and acquiring its lock above, we need to find
+         * another online cpu instead. Such as, this fucntion is being called
+         * on 'new_cpu' at the same time. Can this happen??
+         */
+        if ( !cpu_online(new_cpu) )
+        {
+            spin_unlock(new_lock);
+            goto restart;
+        }
+
+        ASSERT(vmx->pi_blocking.lock == old_lock);
+
+        dest = cpu_physical_id(new_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_blocking.lock = new_lock;
+        spin_unlock(new_lock);
+    }
+
+    spin_unlock_irqrestore(old_lock, flags);
+}
+
 /* This function is called when pcidevs_lock is held */
 void vmx_pi_hooks_assign(struct domain *d)
 {
diff --git a/xen/include/asm-x86/hvm/vmx/vmx.h 
b/xen/include/asm-x86/hvm/vmx/vmx.h
index 4cdd9b1..9783c70 100644
--- a/xen/include/asm-x86/hvm/vmx/vmx.h
+++ b/xen/include/asm-x86/hvm/vmx/vmx.h
@@ -569,6 +569,7 @@ void free_p2m_hap_data(struct p2m_domain *p2m);
 void p2m_init_hap_data(struct p2m_domain *p2m);
 
 void vmx_pi_per_cpu_init(unsigned int cpu);
+void vmx_pi_desc_fixup(int cpu);
 
 void vmx_pi_hooks_assign(struct domain *d);
 void vmx_pi_hooks_deassign(struct domain *d);
-- 
2.1.0


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