Re: [PATCH] drm/i915: Quietly reject attempts to create non-pagealigned stolen objects

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 10 Dec 2014, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Wed, Dec 10, 2014 at 08:17:11AM +0000, Chris Wilson wrote:
>> This added as a BUG_ON as it considered that no one would ever request
>> an unaligned object. However, it turns out that some BIOSes will
>> allocate a scanout that is offset from 0 and not aligned to a page
>> boundary, and we were passing this through and hitting the BUG_ON during
>> boot.
>> 
>> Quietly reject such a request to reserve the unaligned stolen object and
>> let the boot continue, restoring previous behaviour (i.e. no BIOS
>> framebuffer preservation).
>> 
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=86883
>> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
>> Cc: stable@vger.kernel.org
>> ---
>>  drivers/gpu/drm/i915/i915_gem_stolen.c | 10 ++++++----
>>  1 file changed, 6 insertions(+), 4 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
>> index 5c616ec2c5c8..a3bc0fa07c6c 100644
>> --- a/drivers/gpu/drm/i915/i915_gem_stolen.c
>> +++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
>> @@ -646,13 +646,15 @@ i915_gem_object_create_stolen_for_preallocated(struct drm_device *dev,
>>  	DRM_DEBUG_KMS("creating preallocated stolen object: stolen_offset=%x, gtt_offset=%x, size=%x\n",
>>  			stolen_offset, gtt_offset, size);
>>  
>> -	/* KISS and expect everything to be page-aligned */
>> -	BUG_ON(stolen_offset & 4095);
>> -	BUG_ON(size & 4095);
>> -
>>  	if (WARN_ON(size == 0))
>>  		return NULL;
>>  
>> +	/* KISS and expect everything to be GTT page-aligned */
>> +	if ((stolen_offset | size) & 4095) {
>
> Imo we should stil WARN_ON and fixup up the takeover code to align things
> properly ...

Can we fix the regression with Chris' patch and do proper stuff when we
figure out what we want to do?

BR,
Jani.


> -daniel
>
>> +		DRM_DEBUG_KMS("request for unaligned stolen object, denied\n");
>> +		return NULL;
>> +	}
>> +
>>  	stolen = kzalloc(sizeof(*stolen), GFP_KERNEL);
>>  	if (!stolen)
>>  		return NULL;
>> -- 
>> 2.1.3
>> 
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>
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Jani Nikula, Intel Open Source Technology Center
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