memory: Add RAM_PROTECTED flag to skip IOMMU mappings

Add a new RAMBlock flag to denote "protected" memory, i.e. memory that
looks and acts like RAM but is inaccessible via normal mechanisms,
including DMA.  Use the flag to skip protected memory regions when
mapping RAM for DMA in VFIO.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Yang Zhong <yang.zhong@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

4 files changed, 22 insertions, 2 deletions

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 8728d4d..1289cfa 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -562,6 +562,7 @@ static bool vfio_listener_skipped_section(MemoryRegionSection *section)
 {
     return (!memory_region_is_ram(section->mr) &&
             !memory_region_is_iommu(section->mr)) ||
+           memory_region_is_protected(section->mr) ||
            /*
             * Sizing an enabled 64-bit BAR can cause spurious mappings to
             * addresses in the upper part of the 64-bit address space.  These
diff --git a/include/exec/memory.h b/include/exec/memory.h
index c3d417d..9446874 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -190,6 +190,9 @@ typedef struct IOMMUTLBEvent {
  */
 #define RAM_NORESERVE (1 << 7)
 
+/* RAM that isn't accessible through normal means. */
+#define RAM_PROTECTED (1 << 8)
+
 static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn,
                                        IOMMUNotifierFlag flags,
                                        hwaddr start, hwaddr end,
@@ -1267,7 +1270,7 @@ void memory_region_init_ram_from_file(MemoryRegion *mr,
  * @name: the name of the region.
  * @size: size of the region.
  * @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_PMEM,
- *             RAM_NORESERVE.
+ *             RAM_NORESERVE, RAM_PROTECTED.
  * @fd: the fd to mmap.
  * @offset: offset within the file referenced by fd
  * @errp: pointer to Error*, to store an error if it happens.
@@ -1569,6 +1572,16 @@ static inline bool memory_region_is_romd(MemoryRegion *mr)
 }
 
 /**
+ * memory_region_is_protected: check whether a memory region is protected
+ *
+ * Returns %true if a memory region is protected RAM and cannot be accessed
+ * via standard mechanisms, e.g. DMA.
+ *
+ * @mr: the memory region being queried
+ */
+bool memory_region_is_protected(MemoryRegion *mr);
+
+/**
  * memory_region_get_iommu: check whether a memory region is an iommu
  *
  * Returns pointer to IOMMUMemoryRegion if a memory region is an iommu,
diff --git a/softmmu/memory.c b/softmmu/memory.c
index bfedaf9..54cd0e9 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -1811,6 +1811,11 @@ bool memory_region_is_ram_device(MemoryRegion *mr)
     return mr->ram_device;
 }
 
+bool memory_region_is_protected(MemoryRegion *mr)
+{
+    return mr->ram && (mr->ram_block->flags & RAM_PROTECTED);
+}
+
 uint8_t memory_region_get_dirty_log_mask(MemoryRegion *mr)
 {
     uint8_t mask = mr->dirty_log_mask;
diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 23e77cb..088660d 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -2055,7 +2055,8 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
     int64_t file_size, file_align;
 
     /* Just support these ram flags by now. */
-    assert((ram_flags & ~(RAM_SHARED | RAM_PMEM | RAM_NORESERVE)) == 0);
+    assert((ram_flags & ~(RAM_SHARED | RAM_PMEM | RAM_NORESERVE |
+                          RAM_PROTECTED)) == 0);
 
     if (xen_enabled()) {
         error_setg(errp, "-mem-path not supported with Xen");