linux-kernel - Re: [PATCH v2] drm/amdgpu: check vm ready by amdgpu

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Date:   Wed, 23 Feb 2022 15:54:41 +0800
From:   Qiang Yu <yuq825@...il.com>
To:     Paul Menzel <pmenzel@...gen.mpg.de>
Cc:     Qiang Yu <qiang.yu@....com>, David Airlie <airlied@...ux.ie>,
        Xinhui Pan <Xinhui.Pan@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        amd-gfx@...ts.freedesktop.org,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>
Subject: Re: [PATCH v2] drm/amdgpu: check vm ready by amdgpu_vm->evicting flag

On Wed, Feb 23, 2022 at 3:47 PM Paul Menzel <pmenzel@...gen.mpg.de> wrote:
>
> Dear Qiang,
>
>
> Am 22.02.22 um 03:46 schrieb Qiang Yu:
> > 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() latter.
>
> 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
>
> this
>
> > buffer in "evicted" list but no page table in it) gets done
> > immediately.
> >
> > v2: update commit comments.
> >
> > Reviewed-by: Christian König <christian.koenig@....com>
> > Signed-off-by: Qiang Yu <qiang.yu@....com>
> > ---
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 9 +++++++--
> >   1 file changed, 7 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> > index 37acd8911168..2cd9f1a2e5fa 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> > @@ -770,11 +770,16 @@ int amdgpu_vm_validate_pt_bos(struct amdgpu_device *adev, struct amdgpu_vm *vm,
> >    * 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;
> >   }
> >
> >   /**
>
> Acked-by: Paul Menzel <pmenzel@...gen.mpg.de>
>
Thanks, will submit with the typo fixed.

Regards,
Qiang

>
> Kind regards,
>
> Paul