[Qemu-devel] [RFC PATCH 4/8] exec: introduce address_space_get_iotlb_entry()

[Jason Wang <jasowang@redhat.com>]

This patch introduces a helper to query the iotlb entry for a
possible iova. This will be used by later device IOTLB API to enable
the capability for a dataplane (e.g vhost) to query the IOTLB.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Crosthwaite <crosthwaite.peter@gmail.com>
Cc: Richard Henderson <rth@twiddle.net>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 exec.c                | 30 ++++++++++++++++++++++++++++++
 include/exec/memory.h |  7 +++++++
 2 files changed, 37 insertions(+)

diff --git a/exec.c b/exec.c
index f398d21..31fac9f 100644
--- a/exec.c
+++ b/exec.c
@@ -411,6 +411,36 @@ address_space_translate_internal(AddressSpaceDispatch *d, hwaddr addr, hwaddr *x
 }
 
 /* Called from RCU critical section */
+IOMMUTLBEntry address_space_get_iotlb_entry(AddressSpace *as, hwaddr addr,
+                                            bool is_write)
+{
+    IOMMUTLBEntry iotlb = {0};
+    MemoryRegionSection *section;
+    MemoryRegion *mr;
+    hwaddr plen;
+
+    for (;;) {
+        AddressSpaceDispatch *d = atomic_rcu_read(&as->dispatch);
+        section = address_space_translate_internal(d, addr, &addr, &plen, true);
+        mr = section->mr;
+
+        if (!mr->iommu_ops) {
+            break;
+        }
+
+        iotlb = mr->iommu_ops->translate(mr, addr, is_write);
+        if (!(iotlb.perm & (1 << is_write))) {
+            iotlb.target_as = NULL;
+            break;
+        }
+
+        as = iotlb.target_as;
+    }
+
+    return iotlb;
+}
+
+/* Called from RCU critical section */
 MemoryRegion *address_space_translate(AddressSpace *as, hwaddr addr,
                                       hwaddr *xlat, hwaddr *plen,
                                       bool is_write)
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 2de7898..0411a59 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -1310,6 +1310,13 @@ void address_space_stq(AddressSpace *as, hwaddr addr, uint64_t val,
                             MemTxAttrs attrs, MemTxResult *result);
 #endif
 
+
+/* address_space_get_iotlb_entry: translate an address into an IOTLB
+ * entry. Should be called from an RCU critical section.
+ */
+IOMMUTLBEntry address_space_get_iotlb_entry(AddressSpace *as, hwaddr addr,
+                                            bool is_write);
+
 /* address_space_translate: translate an address range into an address space
  * into a MemoryRegion and an address range into that section.  Should be
  * called from an RCU critical section, to avoid that the last reference
-- 
2.5.0