On Sat, Jun 11, 2016 at 09:21:11AM +0100, Chris Wilson wrote:
> One of the first steps in triaging memory corruption on module load is
> to disable stolen. (It helps reduce the impact of the BIOS clobbering
> our memory since we allocate our ringbuffers and initial objects from
> stolen, if they are clobbered we get an immediate hang and garbage on
> screen.) Rather than requesting bug reporters patch their kernel to test
> the theory, allow us to disable stolen through a module option.
Just a quick drive-by observation, intelfb_alloc() calls
i915_gem_object_create_stolen() and if I follow the call chain
in that function it seems to me that dev_priv->mm.stolen_base == 0
isn't checked anywhere, so this looks like something that might break
with i915.enable_stolen=0. But probably that's what you meant with
"secondary effects".
Best regards,
Lukas
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_gem_stolen.c | 5 +++++
> drivers/gpu/drm/i915/i915_params.c | 6 ++++++
> drivers/gpu/drm/i915/i915_params.h | 1 +
> 3 files changed, 12 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
> index e9cd82290408..bb8567b1d6a4 100644
> --- a/drivers/gpu/drm/i915/i915_gem_stolen.c
> +++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
> @@ -411,6 +411,11 @@ int i915_gem_init_stolen(struct drm_device *dev)
> }
> #endif
>
> + if (!i915.enable_stolen) {
> + DRM_INFO("Disabling use of stolen memory at user request.\n");
> + return 0;
> + }
> +
> if (ggtt->stolen_size == 0)
> return 0;
>
> diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
> index 573e78723fc5..511528199aec 100644
> --- a/drivers/gpu/drm/i915/i915_params.c
> +++ b/drivers/gpu/drm/i915/i915_params.c
> @@ -60,6 +60,7 @@ struct i915_params i915 __read_mostly = {
> .enable_dp_mst = true,
> .inject_load_failure = 0,
> .enable_dpcd_backlight = false,
> + .enable_stolen = true,
> };
>
> module_param_named(modeset, i915.modeset, int, 0400);
> @@ -119,6 +120,11 @@ MODULE_PARM_DESC(enable_hangcheck,
> "WARNING: Disabling this can cause system wide hangs. "
> "(default: true)");
>
> +module_param_named(enable_stolen, i915.enable_stolen, bool, 0400);
> +MODULE_PARM_DESC(enable_stolen,
> + "Enable use of memory reserved (stolen) by the BIOS for graphics. "
> + "(default: true)");
> +
> module_param_named_unsafe(enable_ppgtt, i915.enable_ppgtt, int, 0400);
> MODULE_PARM_DESC(enable_ppgtt,
> "Override PPGTT usage. "
> diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
> index 1323261a0cdd..f126decae848 100644
> --- a/drivers/gpu/drm/i915/i915_params.h
> +++ b/drivers/gpu/drm/i915/i915_params.h
> @@ -63,6 +63,7 @@ struct i915_params {
> bool nuclear_pageflip;
> bool enable_dp_mst;
> bool enable_dpcd_backlight;
> + bool enable_stolen;
> };
>
> extern struct i915_params i915 __read_mostly;
> --
> 2.8.1
>
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