[PATCH 2/6] x86/pass-through: no locking around pt_irq_{create,destroy}_bind()

[Jan Beulich <jbeulich@xxxxxxxx>]

The questionable use of pcidevs_lock() there was discussed more than once.
It really is pointless: The functions synchronize primarily via the per-
domain event lock. They also may already be called with the global PCI
devices lock not held: See hvm/vmsi.c:vpci_msi_update(),
hvm/vmsi.c:vpci_msi_arch_update(), and hvm/vmsi.c:vpci_msi_disable().

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

--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -636,10 +636,7 @@ long arch_do_domctl(
             ret = -EPERM;
         else if ( is_iommu_enabled(d) )
         {
-            pcidevs_lock();
             ret = pt_irq_create_bind(d, bind);
-            pcidevs_unlock();
-
             if ( ret < 0 )
                 printk(XENLOG_G_ERR "pt_irq_create_bind failed (%ld) for 
%pd\n",
                        ret, d);
@@ -670,10 +667,7 @@ long arch_do_domctl(
             ret = -EPERM;
         else if ( is_iommu_enabled(d) )
         {
-            pcidevs_lock();
             ret = pt_irq_destroy_bind(d, bind);
-            pcidevs_unlock();
-
             if ( ret < 0 )
                 printk(XENLOG_G_ERR "pt_irq_destroy_bind failed (%ld) for 
%pd\n",
                        ret, d);
--- a/xen/arch/x86/hvm/vioapic.c
+++ b/xen/arch/x86/hvm/vioapic.c
@@ -197,7 +197,6 @@ static int vioapic_hwdom_map_gsi(unsigne
         return ret;
     }
 
-    pcidevs_lock();
     ret = pt_irq_create_bind(currd, &pt_irq_bind);
     if ( ret )
     {
@@ -207,7 +206,6 @@ static int vioapic_hwdom_map_gsi(unsigne
         unmap_domain_pirq(currd, pirq);
         write_unlock(&currd->event_lock);
     }
-    pcidevs_unlock();
 
     return ret;
 }