[Xen-changelog] [xen master] VMX: properly handle pi when all the assigned devices are removed

[patchbot@xxxxxxx]

commit 9152b5f8d917cccd811846d5dd48ade70fbae284
Author:     Feng Wu <feng.wu@xxxxxxxxx>
AuthorDate: Fri Mar 3 17:07:08 2017 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Mar 3 17:07:08 2017 +0100

    VMX: properly handle pi when all the assigned devices are removed
    
    This patch handles some corner cases when the last assigned device
    is removed from the domain. In this case we should carefully handle
    pi descriptor and the per-cpu blocking list, to make sure:
    - all the PI descriptor are in the right state when next time a
    devices is assigned to the domain again.
    - No remaining vcpus of the domain in the per-cpu blocking list.
    
    Here we call vmx_pi_unblock_vcpu() to remove the vCPU from the blocking list
    if it is on the list. However, this could happen when vmx_vcpu_block() is
    being called, hence we might incorrectly add the vCPU to the blocking list
    while the last devcie is detached from the domain. Consider that the 
situation
    can only occur when detaching the last device from the domain and it is not
    a frequent operation, so we use domain_pause before that, which is 
considered
    as an clean and maintainable solution for the situation.
    
    Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
    Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>
---
 xen/arch/x86/hvm/vmx/vmx.c | 29 +++++++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index fe27997..894d7d4 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -154,14 +154,12 @@ static void vmx_pi_switch_to(struct vcpu *v)
     pi_clear_sn(pi_desc);
 }
 
-static void vmx_pi_do_resume(struct vcpu *v)
+static void vmx_pi_unblock_vcpu(struct vcpu *v)
 {
     unsigned long flags;
     spinlock_t *pi_blocking_list_lock;
     struct pi_desc *pi_desc = &v->arch.hvm_vmx.pi_desc;
 
-    ASSERT(!test_bit(_VPF_blocked, &v->pause_flags));
-
     /*
      * Set 'NV' field back to posted_intr_vector, so the
      * Posted-Interrupts can be delivered to the vCPU when
@@ -169,12 +167,12 @@ static void vmx_pi_do_resume(struct vcpu *v)
      */
     write_atomic(&pi_desc->nv, posted_intr_vector);
 
-    /* The vCPU is not on any blocking list. */
     pi_blocking_list_lock = v->arch.hvm_vmx.pi_blocking.lock;
 
     /* Prevent the compiler from eliminating the local variable.*/
     smp_rmb();
 
+    /* The vCPU is not on any blocking list. */
     if ( pi_blocking_list_lock == NULL )
         return;
 
@@ -194,6 +192,13 @@ static void vmx_pi_do_resume(struct vcpu *v)
     spin_unlock_irqrestore(pi_blocking_list_lock, flags);
 }
 
+static void vmx_pi_do_resume(struct vcpu *v)
+{
+    ASSERT(!test_bit(_VPF_blocked, &v->pause_flags));
+
+    vmx_pi_unblock_vcpu(v);
+}
+
 /*
  * To handle posted interrupts correctly, we need to set the following
  * state:
@@ -279,12 +284,23 @@ void vmx_pi_hooks_assign(struct domain *d)
 /* This function is called when pcidevs_lock is held */
 void vmx_pi_hooks_deassign(struct domain *d)
 {
+    struct vcpu *v;
+
     if ( !iommu_intpost || !has_hvm_container_domain(d) )
         return;
 
     ASSERT(d->arch.hvm_domain.pi_ops.vcpu_block);
 
     /*
+     * Pausing the domain can make sure the vCPUs are not
+     * running and hence not calling the hooks simultaneously
+     * when deassigning the PI hooks and removing the vCPU
+     * from the blocking list.
+     */
+    ASSERT(current->domain != d);
+    domain_pause(d);
+
+    /*
      * Note that we don't set 'd->arch.hvm_domain.pi_ops.switch_to' to NULL
      * here. If we deassign the hooks while the vCPU is runnable in the
      * runqueue with 'SN' set, all the future notification event will be
@@ -301,6 +317,11 @@ void vmx_pi_hooks_deassign(struct domain *d)
     d->arch.hvm_domain.pi_ops.vcpu_block = NULL;
     d->arch.hvm_domain.pi_ops.switch_from = NULL;
     d->arch.hvm_domain.pi_ops.do_resume = NULL;
+
+    for_each_vcpu ( d, v )
+        vmx_pi_unblock_vcpu(v);
+
+    domain_unpause(d);
 }
 
 static int vmx_domain_initialise(struct domain *d)
--
generated by git-patchbot for /home/xen/git/xen.git#master

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