[Qemu-devel] [PATCH v2 4/7] memory: provide a MemoryRegion for IOMMUs to log faults

[Avi Kivity <avi@redhat.com>]

Accesses which do not translate will hit the fault region, which
can then log the access.

Signed-off-by: Avi Kivity <avi@redhat.com>
---
 memory.c | 9 ++++++---
 memory.h | 4 ++++
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/memory.c b/memory.c
index ba2d4a0..d6b46fd 100644
--- a/memory.c
+++ b/memory.c
@@ -778,7 +778,9 @@ static void memory_region_destructor_rom_device(MemoryRegion *mr)
 static void memory_region_destructor_iommu(MemoryRegion *mr)
 {
     address_space_destroy(mr->iommu_target_as);
+    address_space_destroy(mr->iommu_fault_as);
     g_free(mr->iommu_target_as);
+    g_free(mr->iommu_fault_as);
 }
 
 static bool memory_region_wrong_endianness(MemoryRegion *mr)
@@ -1001,9 +1003,7 @@ static void memory_region_iommu_rw(MemoryRegion *iommu, hwaddr addr,
             xlat = (tlb.translated_addr & ~tlb.addr_mask) | (addr & tlb.addr_mask);
             address_space_rw(iommu->iommu_target_as, xlat, buf, clen, is_write);
         } else {
-            if (!is_write) {
-                memset(buf, 0xff, clen);
-            }
+            address_space_rw(iommu->iommu_fault_as, addr, buf, clen, is_write);
         }
         buf += clen;
         addr += clen;
@@ -1068,6 +1068,7 @@ static void memory_region_iommu_write(void *opaque, hwaddr addr,
 void memory_region_init_iommu(MemoryRegion *mr,
                               MemoryRegionIOMMUOps *ops,
                               MemoryRegion *target,
+                              MemoryRegion *fault,
                               const char *name,
                               uint64_t size)
 {
@@ -1079,6 +1080,8 @@ void memory_region_init_iommu(MemoryRegion *mr,
     mr->destructor = memory_region_destructor_iommu;
     mr->iommu_target_as = g_new(AddressSpace, 1);
     address_space_init(mr->iommu_target_as, target);
+    mr->iommu_fault_as = g_new(AddressSpace, 1);
+    address_space_init(mr->iommu_fault_as, fault);
 }
 
 static uint64_t invalid_read(void *opaque, hwaddr addr,
diff --git a/memory.h b/memory.h
index 47362c9..6312197 100644
--- a/memory.h
+++ b/memory.h
@@ -162,6 +162,7 @@ struct MemoryRegion {
     unsigned ioeventfd_nb;
     MemoryRegionIoeventfd *ioeventfds;
     struct AddressSpace *iommu_target_as;
+    struct AddressSpace *iommu_fault_as;
 };
 
 struct MemoryRegionPortio {
@@ -361,12 +362,15 @@ void memory_region_init_reservation(MemoryRegion *mr,
  * @ops: a function that translates addresses into the @target region
  * @target: a #MemoryRegion that will be used to satisfy accesses to translated
  *          addresses
+ * @fault: a #MemoryRegion for servicing failed translations; accessed with
+ *         untranslated addresses
  * @name: used for debugging; not visible to the user or ABI
  * @size: size of the region.
  */
 void memory_region_init_iommu(MemoryRegion *mr,
                               MemoryRegionIOMMUOps *ops,
                               MemoryRegion *target,
+                              MemoryRegion *fault,
                               const char *name,
                               uint64_t size);
 
-- 
1.7.12