On Thu, 2022-04-21 at 17:08 +0530, Ramalingam C wrote: > Capture the eviction details for Flat-CCS capable lmem only objects > and > lmem objects with smem residency. This also captures the impact of > eviction on object's memory residency and Flat-CCS compression > state. > > Signed-off-by: Ramalingam C <ramalingam.c@xxxxxxxxx> > --- > drivers/gpu/drm/i915/gt/intel_migrate.c | 36 ++++++++++++++++++----- > -- > 1 file changed, 27 insertions(+), 9 deletions(-) > > diff --git a/drivers/gpu/drm/i915/gt/intel_migrate.c > b/drivers/gpu/drm/i915/gt/intel_migrate.c > index 463a6a14b5f9..9d0d18950e76 100644 > --- a/drivers/gpu/drm/i915/gt/intel_migrate.c > +++ b/drivers/gpu/drm/i915/gt/intel_migrate.c > @@ -485,16 +485,34 @@ static bool wa_1209644611_applies(int ver, u32 > size) > * And CCS data can be copied in and out of CCS region through > * XY_CTRL_SURF_COPY_BLT. CPU can't access the CCS data directly. > * > - * When we exhaust the lmem, if the object's placements support > smem, then we can > - * directly decompress the compressed lmem object into smem and > start using it > - * from smem itself. > + * when we exhaust the lmem, we need to handle two types of flat-ccs > capable > + * objects for its eviction. > + * 1) lmem only objects > + * 2) lmem objects with smem residency option > * > - * But when we need to swapout the compressed lmem object into a > smem region > - * though objects' placement doesn't support smem, then we copy the > lmem content > - * as it is into smem region along with ccs data (using > XY_CTRL_SURF_COPY_BLT). > - * When the object is referred, lmem content will be swaped in along > with > - * restoration of the CCS data (using XY_CTRL_SURF_COPY_BLT) at > corresponding > - * location. > + * 1) lmem only objects: > + * > + * lmem backing memory can be temporarily evicted to smem, along > with the > + * auxiliary CCS state, where it can be potentially swapped-out at a > later point, > + * if required. If userspace later touches the evicted pages, then > we always move > + * the backing memory back to lmem, which includes restoring the > saved CCS state, > + * and potentially performing any required swap-in. > + * > + * In this scenario, objects' backing memory class and Flat-CCS > state doesn't > + * change. > + * > + * 2) lmem objects with smem residency option > + * > + * Lmem object with smem region in it's placement list, will be > migrated into > + * smem by decompressing the content. I915 doesn't handle this kind > of > + * migration for Flat-CCS compressed objects yet. > + * > + * In this scenario, objects' backing memory class and Flat-CCS > state changed, > + * and userspace is not aware of it. > + * > + * In summary, when a userspace wants to be sure about the objects > memory > + * residency and flat-ccs compression state, then placement list > can't have > + * the lmem and smem together. Instead, object has to be lmem > resident only. For 2) I was under the impression that with flat CCS, these objects need to be always uncompressed, since the kernel doesn't have the needed information to decompress / compress. Or has this been changed recently? /Thomas > */ > > static inline u32 *i915_flush_dw(u32 *cmd, u32 flags)
