[Xen-devel] [PATCH 4/4] VT-d PI: Don't add vCPU to PI blocking list for a case

[Chao Gao <chao.gao@xxxxxxxxx>]

Currently, blocked vCPUs are added to PI blocking list if its
domain has assign devices. Actually, some blocked vCPUs will not
be woken up by wakeup interrupt generated by VT-d hardware. They
may be woken up by IPIs or other interrupts from emulated devices.
For these vCPUs we don't add them to PI blocking list.

If a vCPU is blocked prior to its getting bound with a IRTE, we need
adding this vCPU to blocking list when we bind a vCPU with a IRTE.
In that case, arch_vcpu_block() may be called from another vCPU which
the current implementation can't handle. This patch expands the
arch_vcpu_block(), removing some restrictions expressed by
assertions and handling the target vCPU according to its state and
its PI blocking list lock (v->arch.hvm_vmx.pi_blocking.lock).

Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
---
 xen/arch/x86/hvm/vmx/vmx.c             | 21 ++++++++++++++-------
 xen/drivers/passthrough/vtd/intremap.c | 19 +++++++++++++++++++
 2 files changed, 33 insertions(+), 7 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 76cb421..ae16f39 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -125,6 +125,14 @@ static void vmx_vcpu_block(struct vcpu *v)
     struct pi_desc *pi_desc = &v->arch.hvm_vmx.pi_desc;
     spinlock_t *pi_blocking_list_lock;
 
+    /* If no IRTE refers to 'pi_desc', no further operation needs */
+    if ( v->domain->arch.hvm_domain.pi_ops.in_use &&
+         !v->domain->arch.hvm_domain.pi_ops.in_use(v) )
+        return;
+
+    if ( !test_bit(_VPF_blocked, &v->pause_flags) )
+        return;
+
     /*
      * After pCPU goes down, the per-cpu PI blocking list is cleared.
      * To make sure the parameter vCPU is added to the chosen pCPU's
@@ -144,13 +152,8 @@ static void vmx_vcpu_block(struct vcpu *v)
 
     old_lock = cmpxchg(&v->arch.hvm_vmx.pi_blocking.lock, NULL,
                        pi_blocking_list_lock);
-
-    /*
-     * 'v->arch.hvm_vmx.pi_blocking.lock' should be NULL before
-     * being assigned to a new value, since the vCPU is currently
-     * running and it cannot be on any blocking list.
-     */
-    ASSERT(old_lock == NULL);
+    if ( old_lock )
+        goto out;
 
     atomic_inc(&per_cpu(vmx_pi_blocking, dest_cpu).counter);
     HVMTRACE_4D(VT_D_PI_BLOCK, v->domain->domain_id, v->vcpu_id, dest_cpu,
@@ -171,6 +174,10 @@ static void vmx_vcpu_block(struct vcpu *v)
     write_atomic(&pi_desc->nv, pi_wakeup_vector);
     write_atomic(&pi_desc->ndst,
                  (x2apic_enabled ? dest : MASK_INSR(dest, 
PI_xAPIC_NDST_MASK)));
+    return;
+
+ out:
+    spin_unlock_irqrestore(pi_blocking_list_lock, flags);
 }
 
 static void vmx_pi_switch_from(struct vcpu *v)
diff --git a/xen/drivers/passthrough/vtd/intremap.c 
b/xen/drivers/passthrough/vtd/intremap.c
index 99f1cce..c43cfa2 100644
--- a/xen/drivers/passthrough/vtd/intremap.c
+++ b/xen/drivers/passthrough/vtd/intremap.c
@@ -30,6 +30,7 @@
 #include "extern.h"
 
 #include <asm/apic.h>
+#include <asm/hvm/hvm.h>
 #include <asm/io_apic.h>
 #define nr_ioapic_entries(i)  nr_ioapic_entries[i]
 
@@ -622,6 +623,20 @@ static void pi_put_ref(struct pi_desc *pi_desc)
         v->domain->arch.hvm_domain.pi_ops.put_ref(v);
 }
 
+static bool pi_in_use(struct pi_desc *pi_desc)
+{
+    struct vcpu *v;
+
+    if ( !pi_desc )
+        return 0;
+
+    v = pi_desc_to_vcpu(pi_desc);
+    ASSERT(is_hvm_domain(v->domain));
+    if ( v->domain->arch.hvm_domain.pi_ops.in_use )
+        return v->domain->arch.hvm_domain.pi_ops.in_use(v);
+    return 0;
+}
+
 static int msi_msg_to_remap_entry(
     struct iommu *iommu, struct pci_dev *pdev,
     struct msi_desc *msi_desc, struct msi_msg *msg)
@@ -996,6 +1011,7 @@ int pi_update_irte(struct pi_desc *pi_desc, const struct 
pirq *pirq,
     struct msi_desc *msi_desc;
     struct pi_desc *old_pi_desc;
     int rc;
+    bool first_ref;
 
     desc = pirq_spin_lock_irq_desc(pirq, NULL);
     if ( !desc )
@@ -1009,7 +1025,10 @@ int pi_update_irte(struct pi_desc *pi_desc, const struct 
pirq *pirq,
     }
     old_pi_desc = msi_desc->pi_desc;
 
+    first_ref = !pi_in_use(pi_desc);
     pi_get_ref(pi_desc);
+    if ( pi_desc && first_ref )
+        arch_vcpu_block(pi_desc_to_vcpu(pi_desc));
     msi_desc->pi_desc = pi_desc;
     msi_desc->gvec = gvec;
 
-- 
1.8.3.1


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