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

[Chris Wilson]

On Tue, Jan 26, 2016 at 01:13:36AM +0530, ankitprasad.r.sharma at intel.com wrote:
> From: Ankitprasad Sharma <ankitprasad.r.sharma at 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)
> 
> Signed-off-by: Ankitprasad Sharma <ankitprasad.r.sharma at intel.com>

Ideally this would be earlier in the sequence so that we don't introduce
the new API will a known problem.


> ---
>  drivers/gpu/drm/i915/i915_drv.h        | 11 +++++++++++
>  drivers/gpu/drm/i915/i915_gem.c        |  8 ++++++++
>  drivers/gpu/drm/i915/i915_gem_stolen.c | 14 ++++++++++++++
>  drivers/gpu/drm/i915/intel_acpi.c      | 10 ++++++++++
>  4 files changed, 43 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index d77d2ed..8037609 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1311,6 +1311,16 @@ 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 nonvolatile_stolen;
> +
>  	/* the indicator for dispatch video commands on two BSD rings */
>  	unsigned int bsd_ring_dispatch_index;
>  
> @@ -3418,6 +3428,7 @@ 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 9dcefb1..f7c9420 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.nonvolatile_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 335a1ef..4f44531 100644
> --- a/drivers/gpu/drm/i915/i915_gem_stolen.c
> +++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
> @@ -482,6 +482,20 @@ 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.nonvolatile_stolen = true;
> +#ifdef CONFIG_SUSPEND
> +	if (intel_detect_acpi_rst()) {
> +		/* BIOSes using RapidStart Technology have been reported
> +		 * to overwrite stolen across S3, not just S4.
> +		 */
> +		dev_priv->mm.nonvolatile_stolen = false;
> +	}
> +#endif
> +
>  	return 0;
>  }
>  
> diff --git a/drivers/gpu/drm/i915/intel_acpi.c b/drivers/gpu/drm/i915/intel_acpi.c
> index eb638a1..8add47d 100644
> --- a/drivers/gpu/drm/i915/intel_acpi.c
> +++ b/drivers/gpu/drm/i915/intel_acpi.c
> @@ -23,6 +23,11 @@ static const u8 intel_dsm_guid[] = {
>  	0x0f, 0x13, 0x17, 0xb0, 0x1c, 0x2c
>  };
>  
> +static const struct acpi_device_id irst_ids[] = {
> +	{"INT3392", 0},
> +	{"", 0}
> +};

Dead code (atm).

> +
>  static char *intel_dsm_port_name(u8 id)
>  {
>  	switch (id) {
> @@ -162,3 +167,8 @@ void intel_register_dsm_handler(void)
>  void intel_unregister_dsm_handler(void)
>  {
>  }
> +
> +bool intel_detect_acpi_rst(void)
> +{

/* Explain why this code is dead or else we will remove it! */
> +	return true;
> +}

-- 
Chris Wilson, Intel Open Source Technology Centre