linux-kernel - RE: [PATCH 5.16 022/164] drm/amdgpu: check vm ready by amdgpu

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Date:   Mon, 28 Feb 2022 18:24:53 +0000
From:   "Deucher, Alexander" <Alexander.Deucher@....com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Paul Menzel <pmenzel@...gen.mpg.de>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        "Yu, Qiang" <Qiang.Yu@....com>
Subject: RE: [PATCH 5.16 022/164] drm/amdgpu: check vm ready by
 amdgpu_vm->evicting flag

[Public]

> -----Original Message-----
> From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Sent: Monday, February 28, 2022 12:23 PM
> To: linux-kernel@...r.kernel.org
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>;
> stable@...r.kernel.org; Paul Menzel <pmenzel@...gen.mpg.de>; Koenig,
> Christian <Christian.Koenig@....com>; Yu, Qiang <Qiang.Yu@....com>;
> Deucher, Alexander <Alexander.Deucher@....com>
> Subject: [PATCH 5.16 022/164] drm/amdgpu: check vm ready by
> amdgpu_vm->evicting flag
> 
> From: Qiang Yu <qiang.yu@....com>
> 
> commit c1a66c3bc425ff93774fb2f6eefa67b83170dd7e upstream.
> 
> Workstation application ANSA/META v21.1.4 get this error dmesg when
> running CI test suite provided by ANSA/META:
> [drm:amdgpu_gem_va_ioctl [amdgpu]] *ERROR* Couldn't update BO_VA (-
> 16)
> 
> This is caused by:
> 1. create a 256MB buffer in invisible VRAM 2. CPU map the buffer and access
> it causes vm_fault and try to move
>    it to visible VRAM
> 3. force visible VRAM space and traverse all VRAM bos to check if
>    evicting this bo is valuable
> 4. when checking a VM bo (in invisible VRAM), amdgpu_vm_evictable()
>    will set amdgpu_vm->evicting, but latter due to not in visible
>    VRAM, won't really evict it so not add it to amdgpu_vm->evicted 5. before
> next CS to clear the amdgpu_vm->evicting, user VM ops
>    ioctl will pass amdgpu_vm_ready() (check amdgpu_vm->evicted)
>    but fail in amdgpu_vm_bo_update_mapping() (check
>    amdgpu_vm->evicting) and get this error log
> 
> This error won't affect functionality as next CS will finish the waiting VM ops.
> But we'd better clear the error log by checking the amdgpu_vm->evicting flag
> in amdgpu_vm_ready() to stop calling
> amdgpu_vm_bo_update_mapping() later.
> 
> Another reason is amdgpu_vm->evicted list holds all BOs (both user buffer
> and page table), but only page table BOs' eviction prevent VM ops.
> amdgpu_vm->evicting flag is set only for page table BOs, so we should use
> evicting flag instead of evicted list in amdgpu_vm_ready().
> 
> The side effect of this change is: previously blocked VM op (user buffer in
> "evicted" list but no page table in it) gets done immediately.
> 
> v2: update commit comments.
> 
> Acked-by: Paul Menzel <pmenzel@...gen.mpg.de>
> Reviewed-by: Christian König <christian.koenig@....com>
> Signed-off-by: Qiang Yu <qiang.yu@....com>
> Signed-off-by: Alex Deucher <alexander.deucher@....com>
> Cc: stable@...r.kernel.org
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

A regression was reported against this patch in 5.17.  Please drop for now.

Thanks,

Alex

> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c |    9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> @@ -768,11 +768,16 @@ int amdgpu_vm_validate_pt_bos(struct amd
>   * Check if all VM PDs/PTs are ready for updates
>   *
>   * Returns:
> - * True if eviction list is empty.
> + * True if VM is not evicting.
>   */
>  bool amdgpu_vm_ready(struct amdgpu_vm *vm)  {
> -	return list_empty(&vm->evicted);
> +	bool ret;
> +
> +	amdgpu_vm_eviction_lock(vm);
> +	ret = !vm->evicting;
> +	amdgpu_vm_eviction_unlock(vm);
> +	return ret;
>  }
> 
>  /**
>