[RFC V1 02/12] iommufd: no DMA to BARs

[Steve Sistare <steven.sistare@oracle.com>]

Do not map VFIO PCI BARs for DMA.  This stops a raft of warnings of the
following form at QEMU start time when using -object iommufd:

qemu-kvm: warning: IOMMU_IOAS_MAP failed: Bad address, PCI BAR?
qemu-kvm: vfio_container_dma_map(0x555558282db0, 0x8800010000, 0x4000, 0x7ffff7ff0000) = -14 (Bad address)

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
---
 hw/vfio/common.c      | 3 ++-
 hw/vfio/helpers.c     | 1 +
 include/exec/memory.h | 1 +
 3 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index da2e0ec..403d45a 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -248,7 +248,8 @@ static bool vfio_listener_skipped_section(MemoryRegionSection *section)
             * are never accessed by the CPU and beyond the address width of
             * some IOMMU hardware.  TODO: VFIO should tell us the IOMMU width.
             */
-           section->offset_within_address_space & (1ULL << 63);
+           section->offset_within_address_space & (1ULL << 63) ||
+           section->mr->no_dma;
 }
 
 /* Called with rcu_read_lock held.  */
diff --git a/hw/vfio/helpers.c b/hw/vfio/helpers.c
index b14edd4..e4cfdd2 100644
--- a/hw/vfio/helpers.c
+++ b/hw/vfio/helpers.c
@@ -435,6 +435,7 @@ int vfio_region_mmap(VFIORegion *region)
                                           memory_region_owner(region->mem),
                                           name, region->mmaps[i].size,
                                           region->mmaps[i].mmap);
+        region->mmaps[i].mem.no_dma = true;
         g_free(name);
         memory_region_add_subregion(region->mem, region->mmaps[i].offset,
                                     &region->mmaps[i].mem);
diff --git a/include/exec/memory.h b/include/exec/memory.h
index ea03ef2..850cc8c 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -794,6 +794,7 @@ struct MemoryRegion {
     bool unmergeable;
     uint8_t dirty_log_mask;
     bool is_iommu;
+    bool no_dma;
     RAMBlock *ram_block;
     Object *owner;
     /* owner as TYPE_DEVICE. Used for re-entrancy checks in MR access hotpath */
-- 
1.8.3.1