[PATCH 10/10] drm/i915: Disable use of stolen area by User when Intel RST is present

[ankitprasad.r.sharma@intel.com]

From: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>

The BIOS RapidStartTechnology may corrupt the stolen memory across S3
suspend due to unalarmed hibernation, in which case we will not be able
to preserve the User data stored in the stolen region. Hence this patch
tries to identify presence of the RST device on the ACPI bus, and
disables use of stolen memory (for persistent data) if found.

v2: Updated comment, updated/corrected new functions private to driver
(Chris/Tvrtko)

v3: Disabling stolen by default, wait till required acpi changes to
detect device presence are pulled in (Ankit)

v4: Enabled stolen by default as required acpi changes are merged
(Ankit)

v5: renamed variable, is IS_ENABLED() in place of #ifdef, use char*
instead of structures (Lukas)

v6: Return CREATE_VERSION as 1 if stolen memory is volatile due
to presence of Intel RST (CI testing)

Signed-off-by: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
Cc: Lukas Wunner <lukas@wunner.de>
---
 drivers/gpu/drm/i915/i915_dma.c        |  5 ++++-
 drivers/gpu/drm/i915/i915_drv.h        | 11 +++++++++++
 drivers/gpu/drm/i915/i915_gem.c        |  8 ++++++++
 drivers/gpu/drm/i915/i915_gem_stolen.c | 12 ++++++++++++
 drivers/gpu/drm/i915/intel_acpi.c      |  7 +++++++
 5 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 2ae460e..6f8d971 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -173,7 +173,10 @@ static int i915_getparam(struct drm_device *dev, void *data,
 		value = 1;
 		break;
 	case I915_PARAM_CREATE_VERSION:
-		value = 2;
+		if (dev_priv->mm.volatile_stolen)
+			value = 1;
+		else
+			value = 2;
 		break;
 	default:
 		DRM_DEBUG("Unknown parameter %d\n", param->param);
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index f9c580e..50ed31e 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1301,6 +1301,16 @@ struct i915_gem_mm {
 	 */
 	bool busy;
 
+	/**
+	 * Stolen will be lost upon hibernate (as the memory is unpowered).
+	 * Across resume, we expect stolen to be intact - however, it may
+	 * also be utililised by third parties (e.g. Intel RapidStart
+	 * Technology) and if so we have to assume that any data stored in
+	 * stolen across resume is lost and we set this flag to indicate that
+	 * the stolen memory is volatile.
+	 */
+	bool volatile_stolen;
+
 	/* the indicator for dispatch video commands on two BSD rings */
 	unsigned int bsd_ring_dispatch_index;
 
@@ -3427,6 +3437,7 @@ intel_opregion_notify_adapter(struct drm_device *dev, pci_power_t state)
 #endif
 
 /* intel_acpi.c */
+bool intel_detect_acpi_rst(void);
 #ifdef CONFIG_ACPI
 extern void intel_register_dsm_handler(void);
 extern void intel_unregister_dsm_handler(void);
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index e96975a..ddc0d5f 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -396,8 +396,16 @@ static struct drm_i915_gem_object *
 i915_gem_alloc_object_stolen(struct drm_device *dev, size_t size)
 {
 	struct drm_i915_gem_object *obj;
+	struct drm_i915_private *dev_priv = dev->dev_private;
 	int ret;
 
+	if (dev_priv->mm.volatile_stolen) {
+		/* Stolen may be overwritten by external parties
+		 * so unsuitable for persistent user data.
+		 */
+		return ERR_PTR(-ENODEV);
+	}
+
 	mutex_lock(&dev->struct_mutex);
 	obj = i915_gem_object_create_stolen(dev, size);
 	if (IS_ERR(obj))
diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
index 6244dae..9238a79 100644
--- a/drivers/gpu/drm/i915/i915_gem_stolen.c
+++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
@@ -485,6 +485,18 @@ int i915_gem_init_stolen(struct drm_device *dev)
 	 */
 	drm_mm_init(&dev_priv->mm.stolen, 0, dev_priv->gtt.stolen_usable_size);
 
+	/* If the stolen region can be modified behind our backs upon suspend,
+	 * then we cannot use it to store nonvolatile contents (i.e user data)
+	 * as it will be corrupted upon resume.
+	 */
+	dev_priv->mm.volatile_stolen = false;
+	if (IS_ENABLED(CONFIG_SUSPEND)) {
+		/* BIOSes using RapidStart Technology have been reported
+		 * to overwrite stolen across S3, not just S4.
+		 */
+		dev_priv->mm.volatile_stolen = intel_detect_acpi_rst();
+	}
+
 	return 0;
 }
 
diff --git a/drivers/gpu/drm/i915/intel_acpi.c b/drivers/gpu/drm/i915/intel_acpi.c
index eb638a1..05fd67f 100644
--- a/drivers/gpu/drm/i915/intel_acpi.c
+++ b/drivers/gpu/drm/i915/intel_acpi.c
@@ -23,6 +23,8 @@ static const u8 intel_dsm_guid[] = {
 	0x0f, 0x13, 0x17, 0xb0, 0x1c, 0x2c
 };
 
+static const char *irst_id = "INT3392";
+
 static char *intel_dsm_port_name(u8 id)
 {
 	switch (id) {
@@ -162,3 +164,8 @@ void intel_register_dsm_handler(void)
 void intel_unregister_dsm_handler(void)
 {
 }
+
+bool intel_detect_acpi_rst(void)
+{
+	return acpi_dev_present(irst_id);
+}
-- 
1.9.1

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