memory/iommu: Add get_attr()

This adds get_attr() to IOMMUMemoryRegionClass, like
iommu_ops::domain_get_attr in the Linux kernel.

This defines the first attribute - IOMMU_ATTR_SPAPR_TCE_FD - which
will be used between the pSeries machine and VFIO-PCI.
Signed-off-by: NAlexey Kardashevskiy <aik@ozlabs.ru>
Acked-by: NPaolo Bonzini <pbonzini@redhat.com>
Acked-by: NDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: NAlex Williamson <alex.williamson@redhat.com>

include/exec/memory.h

@@ -190,6 +190,10 @@ struct MemoryRegionOps {
     const MemoryRegionMmio old_mmio;
 };
 
+enum IOMMUMemoryRegionAttr {
+    IOMMU_ATTR_SPAPR_TCE_FD
+};
+
 typedef struct IOMMUMemoryRegionClass {
     /* private */
     struct DeviceClass parent_class;
@@ -210,6 +214,10 @@ typedef struct IOMMUMemoryRegionClass {
                                 IOMMUNotifierFlag new_flags);
     /* Set this up to provide customized IOMMU replay function */
     void (*replay)(IOMMUMemoryRegion *iommu, IOMMUNotifier *notifier);
+
+    /* Get IOMMU misc attributes */
+    int (*get_attr)(IOMMUMemoryRegion *iommu, enum IOMMUMemoryRegionAttr,
+                    void *data);
 } IOMMUMemoryRegionClass;
 
 typedef struct CoalescedMemoryRange CoalescedMemoryRange;
@@ -926,6 +934,20 @@ void memory_region_iommu_replay_all(IOMMUMemoryRegion *iommu_mr);
 void memory_region_unregister_iommu_notifier(MemoryRegion *mr,
                                              IOMMUNotifier *n);
 
+/**
+ * memory_region_iommu_get_attr: return an IOMMU attr if get_attr() is
+ * defined on the IOMMU.
+ *
+ * Returns 0 if succeded, error code otherwise.
+ *
+ * @iommu_mr: the memory region
+ * @attr: the requested attribute
+ * @data: a pointer to the requested attribute data
+ */
+int memory_region_iommu_get_attr(IOMMUMemoryRegion *iommu_mr,
+                                 enum IOMMUMemoryRegionAttr attr,
+                                 void *data);
+
 /**
  * memory_region_name: get a memory region's name
  *

memory.c

@@ -1922,6 +1922,19 @@ void memory_region_notify_iommu(IOMMUMemoryRegion *iommu_mr,
     }
 }
 
+int memory_region_iommu_get_attr(IOMMUMemoryRegion *iommu_mr,
+                                 enum IOMMUMemoryRegionAttr attr,
+                                 void *data)
+{
+    IOMMUMemoryRegionClass *imrc = IOMMU_MEMORY_REGION_GET_CLASS(iommu_mr);
+
+    if (!imrc->get_attr) {
+        return -EINVAL;
+    }
+
+    return imrc->get_attr(iommu_mr, attr, data);
+}
+
 void memory_region_set_log(MemoryRegion *mr, bool log, unsigned client)
 {
     uint8_t mask = 1 << client;