We shouldn't blindly unmask the interrupt when resuming. vtd_resume()
will restore the intended state.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -2092,7 +2092,7 @@ static int adjust_vtd_irq_affinities(voi
 }
 __initcall(adjust_vtd_irq_affinities);
 
-static int __must_check init_vtd_hw(void)
+static int __must_check init_vtd_hw(bool resume)
 {
     struct acpi_drhd_unit *drhd;
     struct vtd_iommu *iommu;
@@ -2121,6 +2121,10 @@ static int __must_check init_vtd_hw(void
             disable_qinval(iommu);
         }
 
+        if ( resume )
+            /* FECTL write done by vtd_resume(). */
+            continue;
+
         spin_lock_irqsave(&iommu->register_lock, flags);
         sts = dmar_readl(iommu->reg, DMAR_FECTL_REG);
         sts &= ~DMA_FECTL_IM;
@@ -2320,7 +2324,7 @@ static int __init vtd_setup(void)
     P(iommu_hap_pt_share, "Shared EPT tables");
 #undef P
 
-    ret = init_vtd_hw();
+    ret = init_vtd_hw(false);
     if ( ret )
         goto error;
 
@@ -2590,7 +2594,7 @@ static void vtd_resume(void)
     if ( !iommu_enabled )
         return;
 
-    if ( init_vtd_hw() != 0  && force_iommu )
+    if ( init_vtd_hw(true) != 0 && force_iommu )
          panic("IOMMU setup failed, crash Xen for security purpose\n");
 
     for_each_drhd_unit ( drhd )