Let GVT-g VM read the CSB and CSB write pointer from virtual HWSP, not all
the host support this feature, need to check the BIT(3) of caps in PVINFO.

v3 : Remove unnecessary comments.
v4 : Separate VM enable patch with GVT-g implementation patch due to code
dependency

Signed-off-by: Weinan Li <weinan.z...@intel.com>
Cc: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahti...@linux.intel.com>
---
 drivers/gpu/drm/i915/i915_pvinfo.h     | 1 +
 drivers/gpu/drm/i915/i915_vgpu.c       | 5 +++++
 drivers/gpu/drm/i915/i915_vgpu.h       | 1 +
 drivers/gpu/drm/i915/intel_engine_cs.c | 8 ++++----
 drivers/gpu/drm/i915/intel_lrc.c       | 1 -
 5 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_pvinfo.h 
b/drivers/gpu/drm/i915/i915_pvinfo.h
index 0679a58..195203f 100644
--- a/drivers/gpu/drm/i915/i915_pvinfo.h
+++ b/drivers/gpu/drm/i915/i915_pvinfo.h
@@ -53,6 +53,7 @@ enum vgt_g2v_type {
  * VGT capabilities type
  */
 #define VGT_CAPS_FULL_48BIT_PPGTT      BIT(2)
+#define VGT_CAPS_HWSP_EMULATION                BIT(3)
 
 struct vgt_if {
        u64 magic;              /* VGT_MAGIC */
diff --git a/drivers/gpu/drm/i915/i915_vgpu.c b/drivers/gpu/drm/i915/i915_vgpu.c
index 5fe9f3f..6f713c5 100644
--- a/drivers/gpu/drm/i915/i915_vgpu.c
+++ b/drivers/gpu/drm/i915/i915_vgpu.c
@@ -86,6 +86,11 @@ bool intel_vgpu_has_full_48bit_ppgtt(struct drm_i915_private 
*dev_priv)
        return dev_priv->vgpu.caps & VGT_CAPS_FULL_48BIT_PPGTT;
 }
 
+bool intel_vgpu_has_hwsp_emulation(struct drm_i915_private *dev_priv)
+{
+       return dev_priv->vgpu.caps & VGT_CAPS_HWSP_EMULATION;
+}
+
 struct _balloon_info_ {
        /*
         * There are up to 2 regions per mappable/unmappable graphic
diff --git a/drivers/gpu/drm/i915/i915_vgpu.h b/drivers/gpu/drm/i915/i915_vgpu.h
index b72bd29..cec0ec1 100644
--- a/drivers/gpu/drm/i915/i915_vgpu.h
+++ b/drivers/gpu/drm/i915/i915_vgpu.h
@@ -29,6 +29,7 @@
 void i915_check_vgpu(struct drm_i915_private *dev_priv);
 
 bool intel_vgpu_has_full_48bit_ppgtt(struct drm_i915_private *dev_priv);
+bool intel_vgpu_has_hwsp_emulation(struct drm_i915_private *dev_priv);
 
 int intel_vgt_balloon(struct drm_i915_private *dev_priv);
 void intel_vgt_deballoon(struct drm_i915_private *dev_priv);
diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c 
b/drivers/gpu/drm/i915/intel_engine_cs.c
index a59b2a3..457ebe0 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -25,6 +25,7 @@
 #include <drm/drm_print.h>
 
 #include "i915_drv.h"
+#include "i915_vgpu.h"
 #include "intel_ringbuffer.h"
 #include "intel_lrc.h"
 
@@ -386,10 +387,6 @@ static void intel_engine_init_timeline(struct 
intel_engine_cs *engine)
 
 static bool csb_force_mmio(struct drm_i915_private *i915)
 {
-       /* GVT emulation depends upon intercepting CSB mmio */
-       if (intel_vgpu_active(i915))
-               return true;
-
        /*
         * IOMMU adds unpredictable latency causing the CSB write (from the
         * GPU into the HWSP) to only be visible some time after the interrupt
@@ -398,6 +395,9 @@ static bool csb_force_mmio(struct drm_i915_private *i915)
        if (intel_vtd_active())
                return true;
 
+       if (intel_vgpu_active(i915) && !intel_vgpu_has_hwsp_emulation(i915))
+               return true;
+
        return false;
 }
 
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index fbfcf88..766552f 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -793,7 +793,6 @@ static void intel_lrc_irq_handler(unsigned long data)
                        &engine->status_page.page_addr[I915_HWS_CSB_BUF0_INDEX];
                unsigned int head, tail;
 
-               /* However GVT emulation depends upon intercepting CSB mmio */
                if (unlikely(execlists->csb_use_mmio)) {
                        buf = (u32 * __force)
                                (dev_priv->regs + 
i915_mmio_reg_offset(RING_CONTEXT_STATUS_BUF_LO(engine, 0)));
-- 
1.9.1

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