[PATCH 2 of 2] x86/mm: Make iommu passthrough and mem paging/sharing mutually exclusive

[Andres Lagar-Cavilla <andres@lagarcavilla.org>]

 xen/arch/x86/mm/mem_event.c     |  4 ++++
 xen/arch/x86/mm/mem_sharing.c   |  5 ++++-
 xen/drivers/passthrough/iommu.c |  7 +++++++
 3 files changed, 15 insertions(+), 1 deletions(-)


Regardless of table sharing or processor vendor, these features cannot coexist
since iommu's don't expect gfn->mfn mappings to change, and sharing and paging
depend on trapping all accesses.

Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>

diff -r 92eaf393cad3 -r 1bf42bfcdd45 xen/arch/x86/mm/mem_event.c
--- a/xen/arch/x86/mm/mem_event.c
+++ b/xen/arch/x86/mm/mem_event.c
@@ -567,7 +567,11 @@ int mem_event_domctl(struct domain *d, x
             if ( boot_cpu_data.x86_vendor != X86_VENDOR_INTEL )
                 break;
 
+            /* No paging if iommu is used */
             rc = -EXDEV;
+            if ( unlikely(need_iommu(d)) )
+                break;
+
             /* Disallow paging in a PoD guest */
             if ( p2m->pod.entry_count )
                 break;
diff -r 92eaf393cad3 -r 1bf42bfcdd45 xen/arch/x86/mm/mem_sharing.c
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -1205,8 +1205,11 @@ int mem_sharing_domctl(struct domain *d,
     {
         case XEN_DOMCTL_MEM_SHARING_CONTROL:
         {
-            d->arch.hvm_domain.mem_sharing_enabled = mec->u.enable;
             rc = 0;
+            if ( unlikely(need_iommu(d) && mec->u.enable) )
+                rc = -EXDEV;
+            else
+                d->arch.hvm_domain.mem_sharing_enabled = mec->u.enable;
         }
         break;
 
diff -r 92eaf393cad3 -r 1bf42bfcdd45 xen/drivers/passthrough/iommu.c
--- a/xen/drivers/passthrough/iommu.c
+++ b/xen/drivers/passthrough/iommu.c
@@ -207,6 +207,13 @@ static int assign_device(struct domain *
     if ( !iommu_enabled || !hd->platform_ops )
         return 0;
 
+    /* Prevent device assign if mem paging or mem sharing have been 
+     * enabled for this domain */
+    if ( unlikely(!need_iommu(d) &&
+            (d->arch.hvm_domain.mem_sharing_enabled ||
+             d->mem_event->paging.ring_page)) )
+        return -EXDEV;
+
     spin_lock(&pcidevs_lock);
     if ( (rc = hd->platform_ops->assign_device(d, seg, bus, devfn)) )
         goto done;