Re: [PATCH 1/2] drm/amdgpu: increase the reserved VM size to 2MB

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Am 14.10.20 um 10:26 schrieb Chauhan, Madhav:
> [AMD Public Use]
>
> -----Original Message-----
> From: Christian König <ckoenig.leichtzumerken@gmail.com>
> Sent: Tuesday, October 13, 2020 10:38 PM
> To: amd-gfx@lists.freedesktop.org
> Cc: Chauhan, Madhav <Madhav.Chauhan@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>
> Subject: [PATCH 1/2] drm/amdgpu: increase the reserved VM size to 2MB
>
> Ideally this should be a multiple of the VM block size.
> 2MB should at least fit for Vega/Navi.
>
> Signed-off-by: Christian König <christian.koenig@amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> index 7c46937c1c0e..81ccd0a0c3db 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> @@ -112,8 +112,8 @@ struct amdgpu_bo_list_entry;
>   #define AMDGPU_MMHUB_0				1
>   #define AMDGPU_MMHUB_1				2
>   
> -/* hardcode that limit for now */
> -#define AMDGPU_VA_RESERVED_SIZE			(1ULL << 20)
> +/* Reserve 2MB at top/bottom of address space for kernel use */
> +#define AMDGPU_VA_RESERVED_SIZE			(2ULL << 20)
>
> Looks fine to me: Reviewed-by: Madhav Chauhan <madhav.chauhan@amd.com>
> Clarification on comment:
> We check va_address < AMDGPU_VA_RESERVED_SIZE for invalid reservations, shouldn’t this be "bottom"instead of "top/bottom" of address space??

In amdgpu_info_ioctl() we report AMDGPU_VA_RESERVED_SIZE as start of the 
usable address space and vm_size - AMDGPU_VA_RESERVED_SIZE as end.

Could be that we don't check if the address in the reserved hole at the 
end of the address space. That would be a bug and should probably be fixed.

Christian.

>
> Regards,
> Madhav
>   
>   /* max vmids dedicated for process */
>   #define AMDGPU_VM_MAX_RESERVED_VMID	1

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