Add extended coherence memory flag

Add support for new flag for memory allocation that will provide
system-scope coherent atomics

Change-Id: I426d66223e8d2b570f69b4c0e61145ce9b2290d2

include/linux/kfd_ioctl.h

@@ -1027,6 +1027,7 @@ struct kfd_ioctl_acquire_vm_args {
 #define KFD_IOC_ALLOC_MEM_FLAGS_AQL_QUEUE_MEM	(1 << 27)
 #define KFD_IOC_ALLOC_MEM_FLAGS_COHERENT	(1 << 26)
 #define KFD_IOC_ALLOC_MEM_FLAGS_UNCACHED	(1 << 25)
+#define KFD_IOC_ALLOC_MEM_FLAGS_EXT_COHERENT	(1 << 24)
 
 /* Allocate memory for later SVM (shared virtual memory) mapping.
  *
@@ -1375,6 +1376,8 @@ struct kfd_ioctl_cross_memory_copy_args {
 #define KFD_IOCTL_SVM_FLAG_GPU_READ_MOSTLY     0x00000020
 /* Keep GPU memory mapping always valid as if XNACK is disable */
 #define KFD_IOCTL_SVM_FLAG_GPU_ALWAYS_MAPPED   0x00000040
+/* Fine grained coherency between all devices using device-scope atomics */
+#define KFD_IOCTL_SVM_FLAG_EXT_COHERENT        0x00000080
 
 /**
  * kfd_ioctl_svm_op - SVM ioctl operations