TTM evicting same-vm bos

[Christian König]

Hi Thomas,

sorry for the delayed reply.

On 5/13/25 11:14, Hellstrom, Thomas wrote:
> Hi, Christian
> 
> During eviction we want to be able to evict bos that share the VM's
> reservation object but that are currently not bound to the VM since
> they are not part of the current working set.
> 
> TTM can't handle this situation since it's not aware of whether a bo is
> bound to a VM or not.

That's not 100% true.

We already have support for something similar for the KFD as well, see function amdgpu_ttm_bo_eviction_valuable():

        /* If bo is a KFD BO, check if the bo belongs to the current process.
         * If true, then return false as any KFD process needs all its BOs to
         * be resident to run successfully
         */
        dma_resv_for_each_fence(&resv_cursor, bo->base.resv,
                                DMA_RESV_USAGE_BOOKKEEP, f) {
                if (amdkfd_fence_check_mm(f, current->mm) &&
                    !(place->flags & TTM_PL_FLAG_CONTIGUOUS))
                        return false;
        }

But to be honest I never really liked that approach because it abuses the fact that KFD fences are bound to the struct mm.

Additional to that we have a few flags in the context object which allows to evict BOs with the same resv object during object creation.
 > Do you have a preference of how to address this? One idea would be to
> forward the operation ctx to the eviction_valuable callback. Another to
> add an "unbound" flag to the bo and an "unbound_only" flag to the
> operation ctx.

Adding the ctx to the eviction valuable callback sounds like a good approach to me.

Regards,
Christian.

> 
> Any feedback appreciated.
> Thanks,
> Thomas
> 
> 
>