Return vIOMMU attribute to caller. e.g. VFIO call via PCI layer.

Cc: Kevin Tian <kevin.tian@intel.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Yi Sun <yi.y.sun@linux.intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
---
 hw/i386/intel_iommu.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index 4b22910..a8b7627 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -3436,6 +3436,28 @@ VTDAddressSpace *vtd_find_add_as(IntelIOMMUState *s, PCIBus *bus, int devfn)
     return vtd_dev_as;
 }
 
+static int vtd_dev_get_iommu_attr(PCIBus *bus, void *opaque, int32_t devfn,
+                                   IOMMUAttr attr, void *data)
+{
+    int ret = 0;
+
+    assert(0 <= devfn && devfn < PCI_DEVFN_MAX);
+
+    switch (attr) {
+    case IOMMU_WANT_NESTING:
+    {
+        bool *pdata = data;
+
+        /* return false until vSVA is ready */
+        *pdata = false;
+        break;
+    }
+    default:
+        ret = -ENOENT;
+    }
+    return ret;
+}
+
 static uint64_t get_naturally_aligned_size(uint64_t start,
                                            uint64_t size, int gaw)
 {
@@ -3731,6 +3753,7 @@ static AddressSpace *vtd_host_dma_iommu(PCIBus *bus, void *opaque, int devfn)
 
 static PCIIOMMUOps vtd_iommu_ops = {
     .get_address_space = vtd_host_dma_iommu,
+    .get_iommu_attr = vtd_dev_get_iommu_attr,
 };
 
 static bool vtd_decide_config(IntelIOMMUState *s, Error **errp)
-- 
2.7.4