x86/IOMMU: don't restrict IRQ affinities to online CPUs

In line with "x86/IRQ: desc->affinity should strictly represent the
requested value" the internally used IRQ(s) also shouldn't be restricted
to online ones. Make set_desc_affinity() (set_msi_affinity() then does
by implication) cope with a NULL mask being passed (just like
assign_irq_vector() does), and have IOMMU code pass NULL instead of
&cpu_online_map (when, for VT-d, there's no NUMA node information
available).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
v4: New.

--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -796,18 +796,26 @@ unsigned int set_desc_affinity(struct ir
     unsigned long flags;
     cpumask_t dest_mask;
 
-    if (!cpumask_intersects(mask, &cpu_online_map))
+    if ( mask && !cpumask_intersects(mask, &cpu_online_map) )
         return BAD_APICID;
 
     spin_lock_irqsave(&vector_lock, flags);
-    ret = _assign_irq_vector(desc, mask);
+    ret = _assign_irq_vector(desc, mask ?: TARGET_CPUS);
     spin_unlock_irqrestore(&vector_lock, flags);
 
-    if (ret < 0)
+    if ( ret < 0 )
         return BAD_APICID;
 
-    cpumask_copy(desc->affinity, mask);
-    cpumask_and(&dest_mask, mask, desc->arch.cpu_mask);
+    if ( mask )
+    {
+        cpumask_copy(desc->affinity, mask);
+        cpumask_and(&dest_mask, mask, desc->arch.cpu_mask);
+    }
+    else
+    {
+        cpumask_setall(desc->affinity);
+        cpumask_copy(&dest_mask, desc->arch.cpu_mask);
+    }
     cpumask_and(&dest_mask, &dest_mask, &cpu_online_map);
 
     return cpu_mask_to_apicid(&dest_mask);
--- a/xen/drivers/passthrough/amd/iommu_init.c
+++ b/xen/drivers/passthrough/amd/iommu_init.c
@@ -888,7 +888,7 @@ static void enable_iommu(struct amd_iomm
 
     desc = irq_to_desc(iommu->msi.irq);
     spin_lock(&desc->lock);
-    set_msi_affinity(desc, &cpu_online_map);
+    set_msi_affinity(desc, NULL);
     spin_unlock(&desc->lock);
 
     amd_iommu_msi_enable(iommu, IOMMU_CONTROL_ENABLED);
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -2133,11 +2133,11 @@ static void adjust_irq_affinity(struct a
     const struct acpi_rhsa_unit *rhsa = drhd_to_rhsa(drhd);
     unsigned int node = rhsa ? pxm_to_node(rhsa->proximity_domain)
                              : NUMA_NO_NODE;
-    const cpumask_t *cpumask = &cpu_online_map;
+    const cpumask_t *cpumask = NULL;
     struct irq_desc *desc;
 
     if ( node < MAX_NUMNODES && node_online(node) &&
-         cpumask_intersects(&node_to_cpumask(node), cpumask) )
+         cpumask_intersects(&node_to_cpumask(node), &cpu_online_map) )
         cpumask = &node_to_cpumask(node);
 
     desc = irq_to_desc(drhd->iommu->msi.irq);