Re: [PATCH v2] drm/amdgpu: check vm ready by amdgpu_vm->evicting flag

From: Qiang Yu
Date: Wed Feb 23 2022 - 02:54:56 EST


On Wed, Feb 23, 2022 at 3:47 PM Paul Menzel <pmenzel@xxxxxxxxxxxxx> 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@xxxxxxx>
> > Signed-off-by: Qiang Yu <qiang.yu@xxxxxxx>
> > ---
> > 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@xxxxxxxxxxxxx>
>
Thanks, will submit with the typo fixed.

Regards,
Qiang

>
> Kind regards,
>
> Paul