[V2 1/1] drm/amdgpu/gfx8: add support kernel interface queue(KIQ)

[Christian König]

Am 04.01.2017 um 14:26 schrieb Yu, Xiangliang:
>>>> Am 28.12.2016 um 03:59 schrieb Yu, Xiangliang:
>>>>>> -----Original Message-----
>>>>>> From: amd-gfx [mailto:amd-gfx-bounces at lists.freedesktop.org] On
>>>>>> Behalf Of zhoucm1
>>>>>> Sent: Wednesday, December 28, 2016 10:32 AM
>>>>>> To: Yu, Xiangliang <Xiangliang.Yu at amd.com>; amd-
>>>>>> gfx at lists.freedesktop.org
>>>>>> Cc: Liu, Monk <Monk.Liu at amd.com>
>>>>>> Subject: Re: [V2 1/1] drm/amdgpu/gfx8: add support kernel interface
>>>>>> queue(KIQ)
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 2016年12月28日 10:27, Yu, Xiangliang wrote:
>>>>>>> +
>>>>>>>> +	amdgpu_bo_kunmap(kiq->eop_obj);
>>>>>>>> +
>>>>>> I see it is in many places, which is don't need I think,
>>>>>> amdgpu_bo_free_kernel will handle it if I'm correct.
>>>>> Memory kmap should be free ASAP from memory management point.
>>>> No, that is completely unnecessary as long as you don't run a 32bit
>>>> system with tight address space.
>>> We can't decide what OS to use.  I agree with monk's comment that better
>> to unmap it if cpu don't use.
>>
>> No it isn't. As I said this is only necessary on 32bit systems with tight address
>> space. In other words we simply don't really support that configuration any
>> more.
>>
>> If you don't need it then why do you want to kmap it in the first place?
>>
> In my patch, first get mqd address to fill out mqd context through kmap, then setup compute queue with kiq ring.
>
> And I see there are lot of similar usage in amdgpu, for example, gfx_v8_0_rlc_init function. Could you help to explain it?

Ah! So you only map it initially to fill in some data structure during 
initialization? Yeah, in this case just map the BO temporary, fill in 
the data and unmap it again.

Sorry, judging from the comments I thought that you map/unmap the BO 
multiple times on each IOCTL. That is really something we should try to 
avoid.

Just make sure that you don't store the pointer returned by kmap 
anywhere, it is only valid temporarily.

Regards,
Christian.

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