[PATCH V3] drm/i915/gvt: Allow zero out HWSP addr on hws_pga_write

[Colin Xu]

Guest driver may reset HWSP to 0 as init value during D3->D0:
The full sequence is:
 - Boot ->D0
 - Update HWSP
 - D0->D3
 - ...In D3 state...
 - D3->D0
 - DMLR reset.
 - Set engine HWSP to 0.
 - Set engine ring mode to 0.
 - Set engine HWSP to correct value.
 - Set engine ring mode to correct value.
Ring mode is masked register so set 0 won't take effect.
However HWPS addr 0 is considered as invalid GGTT address which will
report error like:
gvt: vgpu 1: write invalid HWSP address, reg:0x2080, value:0x0
gvt: vgpu 1: fail to emulate MMIO write 00002080 len 4
Detected your guest driver doesn't support GVT-g.
Now vgpu 2 will enter failsafe mode.

Zero out HWSP addr is considered as a valid setting from device driver
so don't treat it as invalid HWSP addr.

V2:
Treat HWSP addr 0 as valid. (zhenyu)

V3:
Change patch title.

Signed-off-by: Colin Xu <colin.xu at intel.com>
---
 drivers/gpu/drm/i915/gvt/handlers.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gvt/handlers.c b/drivers/gpu/drm/i915/gvt/handlers.c
index 3be37e6fe33d..809429a35ec2 100644
--- a/drivers/gpu/drm/i915/gvt/handlers.c
+++ b/drivers/gpu/drm/i915/gvt/handlers.c
@@ -1489,7 +1489,8 @@ static int hws_pga_write(struct intel_vgpu *vgpu, unsigned int offset,
 	const struct intel_engine_cs *engine =
 		intel_gvt_render_mmio_to_engine(vgpu->gvt, offset);
 
-	if (!intel_gvt_ggtt_validate_range(vgpu, value, I915_GTT_PAGE_SIZE)) {
+	if (value != 0 &&
+	    !intel_gvt_ggtt_validate_range(vgpu, value, I915_GTT_PAGE_SIZE)) {
 		gvt_vgpu_err("write invalid HWSP address, reg:0x%x, value:0x%x\n",
 			      offset, value);
 		return -EINVAL;
-- 
2.28.0