drm/i915/gvt: Correct the privilege shadow batch buffer address

Once the ring buffer is copied to ring_scan_buffer and scanned,
the shadow batch buffer start address is only updated into
ring_scan_buffer, not the real ring address allocated through
intel_ring_begin in later copy_workload_to_ring_buffer.

This patch is only to set the right shadow batch buffer address
from Ring buffer, not include the shadow_wa_ctx.

v2:
- refine some comments. (Zhenyu)
v3:
- fix typo in title. (Zhenyu)
v4:
- remove the unnecessary comments. (Zhenyu)
- add comments in bb_start_cmd_va update. (Zhenyu)

Fixes: 0a53bc07f0 ("drm/i915/gvt: Separate cmd scan from request allocation")
Cc: stable@vger.kernel.org  # v4.15
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Yulei Zhang <yulei.zhang@intel.com>
Signed-off-by: fred gao <fred.gao@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

drivers/gpu/drm/i915/gvt/cmd_parser.c

@@ -471,6 +471,7 @@ struct parser_exec_state {
 	 * used when ret from 2nd level batch buffer
 	 */
 	int saved_buf_addr_type;
+	bool is_ctx_wa;
 
 	struct cmd_info *info;
 
@@ -1715,6 +1716,11 @@ static int perform_bb_shadow(struct parser_exec_state *s)
 	bb->accessing = true;
 	bb->bb_start_cmd_va = s->ip_va;
 
+	if ((s->buf_type == BATCH_BUFFER_INSTRUCTION) && (!s->is_ctx_wa))
+		bb->bb_offset = s->ip_va - s->rb_va;
+	else
+		bb->bb_offset = 0;
+
 	/*
 	 * ip_va saves the virtual address of the shadow batch buffer, while
 	 * ip_gma saves the graphics address of the original batch buffer.
@@ -2571,6 +2577,7 @@ static int scan_workload(struct intel_vgpu_workload *workload)
 	s.ring_tail = gma_tail;
 	s.rb_va = workload->shadow_ring_buffer_va;
 	s.workload = workload;
+	s.is_ctx_wa = false;
 
 	if ((bypass_scan_mask & (1 << workload->ring_id)) ||
 		gma_head == gma_tail)
@@ -2624,6 +2631,7 @@ static int scan_wa_ctx(struct intel_shadow_wa_ctx *wa_ctx)
 	s.ring_tail = gma_tail;
 	s.rb_va = wa_ctx->indirect_ctx.shadow_va;
 	s.workload = workload;
+	s.is_ctx_wa = true;
 
 	if (!intel_gvt_ggtt_validate_range(s.vgpu, s.ring_start, s.ring_size)) {
 		ret = -EINVAL;