[Xen-devel] [PATCH v3] x86/mm: don't needlessly veto migration

[Jan Beulich <jbeulich@xxxxxxxx>]

From: Paul Durrant <paul.durrant@xxxxxxxxxx>

Now that xl.cfg has an option to explicitly enable IOMMU mappings for a
domain, migration may be needlessly vetoed due to the check of
is_iommu_enabled() in paging_log_dirty_enable().
There is actually no need to prevent logdirty from being enabled unless
devices are assigned to a domain.

NOTE: While in the neighbourhood, the bool_t parameter type in
      paging_log_dirty_enable() is replaced with a bool and the format
      of the comment in assign_device() is fixed.

Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Release-acked-by: Juergen Gross <jgross@xxxxxxxx>
---
v3:
 - reduce to iommu_use_hap_pt()-less variant
v2:
 - expand commit comment

--- a/xen/arch/x86/mm/hap/hap.c
+++ b/xen/arch/x86/mm/hap/hap.c
@@ -71,7 +71,7 @@ int hap_track_dirty_vram(struct domain *
 
         if ( !paging_mode_log_dirty(d) )
         {
-            rc = paging_log_dirty_enable(d, 0);
+            rc = paging_log_dirty_enable(d, false);
             if ( rc )
                 goto out;
         }
--- a/xen/arch/x86/mm/paging.c
+++ b/xen/arch/x86/mm/paging.c
@@ -209,15 +209,15 @@ static int paging_free_log_dirty_bitmap(
     return rc;
 }
 
-int paging_log_dirty_enable(struct domain *d, bool_t log_global)
+int paging_log_dirty_enable(struct domain *d, bool log_global)
 {
     int ret;
 
-    if ( is_iommu_enabled(d) && log_global )
+    if ( has_arch_pdevs(d) && log_global )
     {
         /*
          * Refuse to turn on global log-dirty mode
-         * if the domain is using the IOMMU.
+         * if the domain is sharing the P2M with the IOMMU.
          */
         return -EINVAL;
     }
@@ -727,7 +727,7 @@ int paging_domctl(struct domain *d, stru
             break;
         /* Else fall through... */
     case XEN_DOMCTL_SHADOW_OP_ENABLE_LOGDIRTY:
-        return paging_log_dirty_enable(d, 1);
+        return paging_log_dirty_enable(d, true);
 
     case XEN_DOMCTL_SHADOW_OP_OFF:
         if ( (rc = paging_log_dirty_disable(d, resuming)) != 0 )
--- a/xen/include/asm-x86/paging.h
+++ b/xen/include/asm-x86/paging.h
@@ -157,7 +157,7 @@ void paging_log_dirty_range(struct domai
                             uint8_t *dirty_bitmap);
 
 /* enable log dirty */
-int paging_log_dirty_enable(struct domain *d, bool_t log_global);
+int paging_log_dirty_enable(struct domain *d, bool log_global);
 
 /* log dirty initialization */
 void paging_log_dirty_init(struct domain *d, const struct log_dirty_ops *ops);

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