From: Xiaolin Zhang <xiaolin.zhang@intel.com>
Date: Fri, 23 Aug 2019 14:57:31 +0800
Subject: drm/i915: to make vgpu ppgtt notificaiton as atomic operation
Git-commit: 9e77f5001b9833a6bdd3940df245053c2212a32b
Patch-mainline: 5.4-rc1
No-fix: 52988009843160c5b366b4082ed6df48041c655c
References: bnc#1151927 5.3.6

vgpu ppgtt notification was split into 2 steps, the first step is to
update PVINFO's pdp register and then write PVINFO's g2v_notify register
with action code to tirgger ppgtt notification to GVT side.

currently these steps were not atomic operations due to no any protection,
so it is easy to enter race condition state during the MTBF, stress and
IGT test to cause GPU hang.

the solution is to add a lock to make vgpu ppgtt notication as atomic
operation.

Cc: stable@vger.kernel.org
Signed-off-by: Xiaolin Zhang <xiaolin.zhang@intel.com>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/1566543451-13955-1-git-send-email-xiaolin.zhang@intel.com
(cherry picked from commit 52988009843160c5b366b4082ed6df48041c655c)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/gpu/drm/i915/i915_drv.h     |    1 +
 drivers/gpu/drm/i915/i915_gem_gtt.c |   12 +++++++-----
 drivers/gpu/drm/i915/i915_vgpu.c    |    1 +
 3 files changed, 9 insertions(+), 5 deletions(-)

--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1075,6 +1075,7 @@ struct i915_frontbuffer_tracking {
 };
 
 struct i915_virtual_gpu {
+	struct mutex lock; /* serialises sending of g2v_notify command pkts */
 	bool active;
 	u32 caps;
 };
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -830,10 +830,9 @@ static void mark_tlbs_dirty(struct i915_
 	ppgtt->pd_dirty_engines = ALL_ENGINES;
 }
 
-static int gen8_ppgtt_notify_vgt(struct i915_ppgtt *ppgtt, bool create)
+static void gen8_ppgtt_notify_vgt(struct i915_ppgtt *ppgtt, bool create)
 {
-	struct i915_address_space *vm = &ppgtt->vm;
-	struct drm_i915_private *dev_priv = vm->i915;
+	struct drm_i915_private *dev_priv = ppgtt->vm.i915;
 	enum vgt_g2v_type msg;
 	int i;
 
@@ -842,7 +841,9 @@ static int gen8_ppgtt_notify_vgt(struct
 	else
 		atomic_dec(px_used(ppgtt->pd));
 
-	if (i915_vm_is_4lvl(vm)) {
+	mutex_lock(&dev_priv->vgpu.lock);
+
+	if (i915_vm_is_4lvl(&ppgtt->vm)) {
 		const u64 daddr = px_dma(ppgtt->pd);
 
 		I915_WRITE(vgtif_reg(pdp[0].lo), lower_32_bits(daddr));
@@ -862,9 +863,10 @@ static int gen8_ppgtt_notify_vgt(struct
 				VGT_G2V_PPGTT_L3_PAGE_TABLE_DESTROY);
 	}
 
+	/* g2v_notify atomically (via hv trap) consumes the message packet. */
 	I915_WRITE(vgtif_reg(g2v_notify), msg);
 
-	return 0;
+	mutex_unlock(&dev_priv->vgpu.lock);
 }
 
 /* Index shifts into the pagetable are offset by GEN8_PTE_SHIFT [12] */
--- a/drivers/gpu/drm/i915/i915_vgpu.c
+++ b/drivers/gpu/drm/i915/i915_vgpu.c
@@ -95,6 +95,7 @@ void i915_detect_vgpu(struct drm_i915_pr
 	dev_priv->vgpu.caps = readl(shared_area + vgtif_offset(vgt_caps));
 
 	dev_priv->vgpu.active = true;
+	mutex_init(&dev_priv->vgpu.lock);
 	DRM_INFO("Virtual GPU for Intel GVT-g detected.\n");
 
 out: