On Mon, 2022-01-24 at 17:24 +0100, Thomas Hellström wrote: > Hi, Adrian > > On 1/21/22 23:22, Adrian Larumbe wrote: > > When a flat-CCS lmem-bound BO is evicted onto smem for the first > > time, a > > separate swap gem object is created to hold the contents of the CCS > > block. > > It is assumed that, for a flat-CCS bo to be migrated back onto > > lmem, it > > should've begun its life in lmem. > > > > It also handles destruction of the swap bo when the original TTM > > object > > reaches the end of its life. > > > > Signed-off-by: Adrian Larumbe <adrian.larumbe@xxxxxxxxxxxxx> > > > While allocating a separate object for the CCS data is certainly > possible, it poses some additional difficulties that have not been > addressed here. > > The CCS object needs to share the dma_resv of the original object. > That > is because the CCS object needs to be locked and validated when we > process it, and we > can only trylock within the ttm move callback which might therefore > fail > and isn't sufficient on swapin. We'd need to create some > i915_gem_object_create_region_locked() that wraps > ttm_bo_init_reserved(). Actually that would be a function to create with a reservation object shared from another object. /Thomas
