Re: [PATCH 3/3] drm/amdgpu: more descriptive message if HMM not enabled

["Yang, Philip" <Philip.Yang-5C7GfCeVMHo@public.gmane.org>]

On 2019-03-06 4:05 a.m., Michel Dänzer wrote:
> On 2019-03-05 7:09 p.m., Yang, Philip wrote:
>> If using old kernel config file, CONFIG_ZONE_DEVICE is not selected,
>> so CONFIG_HMM and CONFIG_HMM_MIRROR is not enabled, the current driver
>> error message "Failed to register MMU notifier" is not clear. Inform
>> user with more descriptive message on how to fix the missing kernel
>> config option.
>>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109808
>>
>> Change-Id: Idfebaeababa4c37c1ef093c2b91a26910a167585
>> Signed-off-by: Philip Yang <Philip.Yang@amd.com>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_mn.h | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.h
>> index 4803e216e174..b155cac52aca 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.h
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.h
>> @@ -53,6 +53,8 @@ static inline struct amdgpu_mn *amdgpu_mn_get(struct amdgpu_device *adev,
>>   }
>>   static inline int amdgpu_mn_register(struct amdgpu_bo *bo, unsigned long addr)
>>   {
>> +	DRM_ERROR("HMM_MIRROR kernel config option is not enabled\n");
>> +	DRM_ERROR("add CONFIG_ZONE_DEVICE=y in config file to fix this\n");
>>   	return -ENODEV;
>>   }
>>   static inline void amdgpu_mn_unregister(struct amdgpu_bo *bo) {}
>>
> 
> amdgpu_gem_userptr_ioctl calls amdgpu_mn_register if userspace sets the
> AMDGPU_GEM_USERPTR_REGISTER flag, so buggy/malicious userspace could
> spam dmesg with these errors. I'm afraid a different solution is needed.
> 
> The error message is inside dummy function amdgpu_mn_register, it only 
shows if kernel config option HMM is not enabled. Driver does need HMM 
kernel option to support userptr. We want to provide obvious message to 
users to update kernel config file from old kernel, otherwise all 
userptr related functions are broken. I will change this to WARN_ONCE to 
avoid spam dmesg.

Regards,
Philip
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