Re: [PATCH] drm/amdgpu: csa_vaddr should not larger than AMDGPU_GMC_HOLE_START

["Koenig, Christian" <Christian.Koenig-5C7GfCeVMHo@public.gmane.org>]

Am 15.01.19 um 07:19 schrieb Liu, Monk:
> The max_pfn is now 1'0000'0000'0000'0000 (bytes) which is above 48 bit now, and it with AMDGPU_GMC_HOLE_MASK make it to zero ....
>
> And in code "amdgpu_driver_open_kms()" I saw @Zhu, Rex write the code as :
>
> "csa_addr = amdgpu_csa_vadr(adev) & AMDGPU_GMC_HOLE_MASK", I think this is wrong since you intentionally place the csa above GMC hole, right ?

The fix is just completely incorrect since min(adev->vm_manager.max_pfn 
<< AMDGPU_GPU_PAGE_SHIFT, AMDGPU_GMC_HOLE_START) still gives you 0 when 
we shift max_pfn to much to the left.

The correct solution is to substract the reserved size first and then 
shift. E.g.:

addr = (max_pfn - (AMDGPU_VA_RESERVED_SIZE >> AMDGPU_PAGE_SHIFT)) << 
AMDGPU_PAGE_SHIFT;

Regards,
Christian.

>
> Looks like  we should modify this place
>
> /Monk
>
> -----Original Message-----
> From: amd-gfx <amd-gfx-bounces@lists.freedesktop.org> On Behalf Of Christian K?nig
> Sent: Monday, January 14, 2019 9:05 PM
> To: Lou, Wentao <Wentao.Lou@amd.com>; amd-gfx@lists.freedesktop.org
> Subject: Re: [PATCH] drm/amdgpu: csa_vaddr should not larger than AMDGPU_GMC_HOLE_START
>
> Am 14.01.19 um 09:40 schrieb wentalou:
>> After removing unnecessary VM size calculations, vm_manager.max_pfn
>> would reach 0x10,0000,0000 max_pfn << AMDGPU_GPU_PAGE_SHIFT exceeding
>> AMDGPU_GMC_HOLE_START would caused GPU reset.
>>
>> Change-Id: I47ad0be2b0bd9fb7490c4e1d7bb7bdacf71132cb
>> Signed-off-by: wentalou <Wentao.Lou@amd.com>
> NAK, that is incorrect. We intentionally place the csa above the GMC hole.
>
> Regards,
> Christian.
>
>> ---
>>    drivers/gpu/drm/amd/amdgpu/amdgpu_csa.c | 3 ++-
>>    1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_csa.c
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_csa.c
>> index 7e22be7..dd3bd01 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_csa.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_csa.c
>> @@ -26,7 +26,8 @@
>>    
>>    uint64_t amdgpu_csa_vaddr(struct amdgpu_device *adev)
>>    {
>> -	uint64_t addr = adev->vm_manager.max_pfn << AMDGPU_GPU_PAGE_SHIFT;
>> +	uint64_t addr = min(adev->vm_manager.max_pfn << AMDGPU_GPU_PAGE_SHIFT,
>> +				AMDGPU_GMC_HOLE_START);
>>    
>>    	addr -= AMDGPU_VA_RESERVED_SIZE;
>>    	addr = amdgpu_gmc_sign_extend(addr);
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