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

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Date:   Mon, 28 Feb 2022 22:33:04 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     "Deucher, Alexander" <Alexander.Deucher@....com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "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

On Mon, Feb 28, 2022 at 06:24:53PM +0000, Deucher, Alexander wrote:
> [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.

Dropped from 5.10.y, 5.15.y, and 5.16.y.  Please feel free to send it to
stable@...r.kernel.org when it is now working correctly.

thanks,

greg k-h