drm/xe: NULL binding implementation

Add uAPI and implementation for NULL bindings. A NULL binding is defined
as writes dropped and read zero. A single bit in the uAPI has been added
which results in a single bit in the PTEs being set.

NULL bindings are intendedd to be used to implement VK sparse bindings,
in particular residencyNonResidentStrict property.

v2: Fix BUG_ON shown in VK testing, fix check patch warning, fix
xe_pt_scan_64K, update __gen8_pte_encode to understand NULL bindings,
remove else if vma_addr

Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Suggested-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/uapi/drm/xe_drm.h b/include/uapi/drm/xe_drm.h
index 83868af45984..6a991afc563d 100644
--- a/include/uapi/drm/xe_drm.h
+++ b/include/uapi/drm/xe_drm.h
@@ -418,6 +418,14 @@ struct drm_xe_vm_bind_op {
 	 * than differing the MAP to the page fault handler.
 	 */
 #define XE_VM_BIND_FLAG_IMMEDIATE	(0x1 << 18)
+	/*
+	 * When the NULL flag is set, the page tables are setup with a special
+	 * bit which indicates writes are dropped and all reads return zero.  In
+	 * the future, the NULL flags will only be valid for XE_VM_BIND_OP_MAP
+	 * operations, the BO handle MBZ, and the BO offset MBZ. This flag is
+	 * intended to implement VK sparse bindings.
+	 */
+#define XE_VM_BIND_FLAG_NULL		(0x1 << 19)
 
 	/** @reserved: Reserved */
 	__u64 reserved[2];