[xen master] x86/pass-through: alter locking around pt_irq_{create,destroy}_bind()

[patchbot@xxxxxxx]

commit d70db94288f0cbf739c424292f75e2e05669d45d
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Oct 29 09:08:45 2026 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Oct 29 09:08:45 2026 +0100

    x86/pass-through: alter locking around pt_irq_{create,destroy}_bind()
    
    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().
    
    It's merely msixtbl_pt_{,un}register() which require the global or per-
    domain PCI lock held. Switch to using the latter, which is also sufficient
    to acquire in read mode. While strictly speaking this is needed only for
    PT_IRQ_TYPE_MSI, keep it being unconditional. In vioapic_hwdom_map_gsi()
    also unlock earlier.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger@xxxxxxxxxxxxxx>
---
 xen/arch/x86/domctl.c      | 8 ++++----
 xen/arch/x86/hvm/vioapic.c | 4 ++--
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
index 51d62617bb..1e00510702 100644
--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -636,9 +636,9 @@ long arch_do_domctl(
             ret = -EPERM;
         else if ( is_iommu_enabled(d) )
         {
-            pcidevs_lock();
+            read_lock(&d->pci_lock);
             ret = pt_irq_create_bind(d, bind);
-            pcidevs_unlock();
+            read_unlock(&d->pci_lock);
 
             if ( ret < 0 )
                 printk(XENLOG_G_ERR "pt_irq_create_bind failed (%ld) for 
%pd\n",
@@ -670,9 +670,9 @@ long arch_do_domctl(
             ret = -EPERM;
         else if ( is_iommu_enabled(d) )
         {
-            pcidevs_lock();
+            read_lock(&d->pci_lock);
             ret = pt_irq_destroy_bind(d, bind);
-            pcidevs_unlock();
+            read_unlock(&d->pci_lock);
 
             if ( ret < 0 )
                 printk(XENLOG_G_ERR "pt_irq_destroy_bind failed (%ld) for 
%pd\n",
diff --git a/xen/arch/x86/hvm/vioapic.c b/xen/arch/x86/hvm/vioapic.c
index 222e59e2c2..b633f15232 100644
--- a/xen/arch/x86/hvm/vioapic.c
+++ b/xen/arch/x86/hvm/vioapic.c
@@ -197,7 +197,7 @@ static int vioapic_hwdom_map_gsi(unsigned int gsi, unsigned 
int trig,
         return ret;
     }
 
-    pcidevs_lock();
+    read_lock(&currd->pci_lock);
     ret = pt_irq_create_bind(currd, &pt_irq_bind);
     if ( ret )
     {
@@ -207,7 +207,7 @@ static int vioapic_hwdom_map_gsi(unsigned int gsi, unsigned 
int trig,
         unmap_domain_pirq(currd, pirq);
         write_unlock(&currd->event_lock);
     }
-    pcidevs_unlock();
+    read_unlock(&currd->pci_lock);
 
     return ret;
 }
--
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