Re: [Intel-gfx] [PATCH] drm/i915/huc: Fix error reported by I915_PARAM_HUC_STATUS

["Fosha, Robert M" <robert.m.fosha@intel.com>]

On 2/11/20 11:57 AM, Michal Wajdeczko wrote:
> On Tue, 11 Feb 2020 18:53:05 +0100, Fosha, Robert M 
> <robert.m.fosha@intel.com> wrote:
>
>>
>>
>> On 2/4/20 4:43 PM, Ye, Tony wrote:
>>>
>>>
>>> On 1/27/2020 1:41 AM, Michal Wajdeczko wrote:
>>>> On Thu, 23 Jan 2020 16:51:58 +0100, Chris Wilson 
>>>> <chris@chris-wilson.co.uk> wrote:
>>>>
>>>>> Quoting Michal Wajdeczko (2020-01-23 15:38:52)
>>>>>> On Thu, 23 Jan 2020 16:02:17 +0100, Chris Wilson
>>>>>> <chris@chris-wilson.co.uk> wrote:
>>>>>>
>>>>>> > Quoting Daniele Ceraolo Spurio (2020-01-22 23:52:33)
>>>>>> >>
>>>>>> >>
>>>>>> >> On 1/22/20 11:48 AM, Michal Wajdeczko wrote:
>>>>>> >> >  From commit 84b1ca2f0e68 ("drm/i915/uc: prefer intel_gt 
>>>>>> over i915
>>>>>> >> > in GuC/HuC paths") we stopped using HUC_STATUS error -ENODEV 
>>>>>> only
>>>>>> >> > to indicate lack of HuC hardware and we started to use this 
>>>>>> error
>>>>>> >> > also for all other cases when HuC was not in use or supported.
>>>>>> >> >
>>>>>> >> > Fix that by relying again on HAS_GT_UC macro, since currently
>>>>>> >> > used function intel_huc_is_supported() is based on HuC firmware
>>>>>> >> > support which could be unsupported also due to force disabled
>>>>>> >> > GuC firmware.
>>>>>> >> >
>>>>>> >> > Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
>>>>>> >> > Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
>>>>>> >> > Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
>>>>>> >> > Cc: Tony Ye <tony.ye@intel.com>
>>>>>> >>
>>>>>> >> Reviewed-by: Daniele Ceraolo Spurio 
>>>>>> <daniele.ceraolospurio@intel.com>
>>>>>> >
>>>>>> > Once upon a time did you (Michal) not argue we should indicate 
>>>>>> the lack
>>>>>> > of firmware in the error code? Something like
>>>>>> >
>>>>>> > if (!HAS_GT_UC(gt->i915))
>>>>>> >       return -ENODEV;
>>>>>> >
>>>>>> > if (!intel_huc_is_supported(huc))
>>>>>> >       return -ENOEXEC;
>>>>>>
>>>>>> Yes, we discussed this here [1] together with [2] but we didn't
>>>>>> conclude our discussion due to different opinions on how represent
>>>>>> some states, in particular "manually disabled" state.
>>>>>>
>>>>>> In this patch I just wanted to restore old notation.
>>>>>>
>>>>>> But we can start new discussion, here is summary:
>>>>>>
>>>>>> ------------------+----------+----------+----------
>>>>>>   HuC state        | today*   | option A | option B
>>>>>> ------------------+----------+----------+----------
>>>>>> no HuC hardware   | -ENODEV  | -ENODEV  | -ENODEV
>>>>>> GuC fw disabled   |   0      |     0    | -EOPNOTSUPP
>>>>>> HuC fw disabled   |   0      |     0    | -EOPNOTSUPP
>>>>>> HuC fw missing    |   0      | -ENOPKG  | -ENOEXEC
>>>>>> HuC fw error      |   0      | -ENOEXEC | -ENOEXEC
>>>>>> HuC fw fail       |   0      | -EACCES  |    0
>>>>>> HuC authenticated |   1      |     1    |    1
>>>>>> ------------------+----------+----------+----------
>>>>>
>>>>> By fw fail, you mean we loaded the firmware (to our knowledge)
>>>>> correctly, but HUC_STATUS is not reported as valid?
>>>>>
>>>>> If so, I support option B. I like the idea of saying
>>>>> "no HuC" (machine too old)
>>>>> "no firmware" (user action, or lack thereof)
>>>>> 0 (fw unhappy)
>>>>> 1 (fw reports success)
>>>>>
>>>>> In between states for failures in fw loading? Not so sure. But I 
>>>>> can see
>>>>> the nicety in distinguishing between lack of firmware and some random
>>>>> failure in loading the firmware (the former being user action 
>>>>> required
>>>>> to rectify, command line parameter whatever and the latter being the
>>>>> firmware file is either invalid or a stray neutrino prevented 
>>>>> loading).
>>>>>
>>>>> Imo the error messages should be about why we cannot probe/trust the
>>>>> HUC_STATUS register. If everything is setup correctly then the 
>>>>> returned
>>>>> value should be from reading the register. I dislike only 
>>>>> returning 1 if
>>>>> supported, and converting a valid read of 0 into another error.
>>>>>
>>>>> So Option B :)
>>>>
>>>> But I'm not sure that option B is consistent in error reporting, as
>>>> "fw unhappy" is definitely an serious error but is represented as 
>>>> plain
>>>> non-error "0" status, while "fw disabled" (user action) is treated 
>>>> as error
>>>>
>>>> ------------------+----------
>>>>    HuC state       | option B
>>>> ------------------+----------
>>>> no HuC hardware   | -ENODEV
>>>> GuC fw disabled   | -EOPNOTSUPP -> user decision, why error?
>>>> HuC fw disabled   | -EOPNOTSUPP -> user decision, why error?
>>>> HuC fw missing    | -ENOEXEC
>>>> HuC fw error      | -ENOEXEC
>>>> HuC fw fail       |    0        -> unlikely, but still fw/hw error
>>>> HuC authenticated |    1
>>>> ------------------+----------
>>>>
>>>> On other hand, option A treats all error conditions as errors, leaving
>>>> status codes only for normal operations: disabled(0)/authenticated(1):
>>>>
>>>> ------------------+----------
>>>>    HuC state       | option A
>>>> ------------------+----------
>>>> no HuC hardware   | -ENODEV  -> you shouldn't ask
>>>> GuC fw disabled   |     0    -> user decision, not an error
>>>> HuC fw disabled   |     0    -> user decision, not an error
>>>> HuC fw missing    | -ENOPKG  -> fw not installed correctly
>>>> HuC fw error      | -ENOEXEC -> bad/wrong fw
>>>> HuC fw fail       | -EACCES  -> fw/hw error
>>>> HuC authenticated |     1
>>>> ------------------+----------
>>>
>>> Vote for Option A.
>>>
>>> Regards,
>>> Tony
>>>
>>
>> Are we ok to move forward on this? Michal, are you working on 
>> updating the patch?
>
> I can update the patch, but I don't know which option to implement:
> Tony votes for Option A, Chris for Option B, what's your choice?
>
> Michal
>

I don't have a preference and would trust both Tony and Chris over 
myself. However, if Tony is using HuC more I would vote for his prefered 
option.

-Rob

>>
>> -Rob
>>
>>>>
>>>> But since I'm not an active HuC user, will leave final decision to 
>>>> others.
>>>>
>>>> /Michal
>>>>
>>>>
>>>>>
>>>>>> Note that all above should be compatible with media driver,
>>>>>> which explicitly looks for no error and value 1
>>>>>
>>>>> Cool.
>>>>> -Chris
>>> _______________________________________________
>>> Intel-gfx mailing list
>>> Intel-gfx@lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

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