[Intel-gfx] [RFC PATCH v3 1/1] i915/drm: Split out x86/arm64 for run_as_guest

[Jani Nikula]

On Tue, 22 Mar 2022, Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com> wrote:
> On 22/03/2022 14:49, Jani Nikula wrote:
>> On Tue, 22 Mar 2022, Lucas De Marchi <lucas.demarchi at intel.com> wrote:
>>> On Tue, Mar 22, 2022 at 12:21:59PM +0200, Jani Nikula wrote:
>>>> On Mon, 21 Mar 2022, Lucas De Marchi <lucas.demarchi at intel.com> wrote:
>>>>> On Mon, Mar 21, 2022 at 04:34:49PM -0700, Casey Bowman wrote:
>>>>>> Wanted to ping this older thread to find out where we stand with this patch,
>>>>>> Are we OK with the current state of these changes?
>>>>>>
>>>>>> With more recent information gathered from feedback on other patches, would
>>>>>> we prefer changing this to a more arch-neutral control flow?
>>>>>>
>>>>>> e.g.
>>>>>> #if IS_ENABLED(CONFIG_X86)
>>>>>> ...
>>>>>> #else
>>>>>> ...
>>>>>> #endif
>>>>>>
>>>>>> Would we also prefer this RFC series be merged or would it be preferred to
>>>>>> create a new series instead?
>>>>>
>>>>> for this specific function, that is used in only 2 places I think it's
>>>>> ok to do:
>>>>>
>>>>> 	static inline bool run_as_guest(void)
>>>>> 	{
>>>>> 	#if IS_ENABLED(CONFIG_X86)
>>>>> 		return !hypervisor_is_type(X86_HYPER_NATIVE);
>>>>> 	#else	
>>>>> 		/* Not supported yet */
>>>>> 		return false;	
>>>>> 	#endif
>>>>> 	}
>>>>>
>>>>> For PCH it doesn't really matter as we don't execute that function
>>>>> for discrete. For intel_vtd_active() I figure anything other than
>>>>> x86 would be fine with false here.
>>>>>
>>>>> Jani, that this look good to you?
>>>>
>>>> It's more important to me to get this out of i915_drv.h, which is not
>>>> supposed to be a collection of random stuff anymore. I've sent patches
>>>> to this effect but they've stalled a bit.
>>>
>>> do you have a patch moving this particular one? got a link?
>> 
>> Yeah, but it was basically shot down by Tvrtko [1], and I stalled there.
>> 
>> I'd just like to get all this cruft out of i915_drv.h. Whenever we have
>> a file where the name isn't super specific, we seem to have a tendency
>> of turning it into a dumping ground for random crap. So I'd really like
>> to move this out of there *before* expanding on it.
>
> Sounds like we had agreement on what tweaks to make and I conceded to 
> live for now with the IMO wrongly named intel_vtd_run_as_guest.
>
> (I mean I really disagree with file name being trumps, which I think 
> this example illustrates - this is i915 asking whether the kernel is 
> running as guest so intel_vtd_ prefix is just wrong. Intel VT-d is the 
> iommu thingy so it makes no sense when called from PCH detection. But I 
> have no better ideas at the moment. We can call it i915_run_as_guest, to 
> signify function belongs to i915, but then we lose the first parameter 
> names the function rule.)

I think the "first parameter names the function" rule has backfired in
gem/gt land, because it's pretty difficult to figure out *where* you'd
expect to find or place functions.

BR,
Jani.

>
> But in any case I don't see that I created any blockers in this thread. 
> AFAICS just a respin with intel_vtd_active taking struct device is 
> needed and job done.
>
> Regards,
>
> Tvrtko

-- 
Jani Nikula, Intel Open Source Graphics Center