On Mon, Feb 03, 2025 at 10:21:53AM +0100, Boris Brezillon wrote: > +Akash with whom we've been discussing adding a 'REPEAT' mode to > drm_gpuvm/panthor. > > On Sun, 2 Feb 2025 19:53:47 +0100 > Danilo Krummrich <dakr@xxxxxxxxxx> wrote: > > > Hi Lina, > > > > On Sun, Feb 02, 2025 at 10:34:49PM +0900, Asahi Lina wrote: > > > Some hardware requires dummy page mappings to efficiently implement > > > Vulkan sparse features. These mappings consist of the same physical > > > memory page, repeated for a large range of address space (e.g. 16GiB). > > > > > > Add support for this to drm_gpuvm. Currently, drm_gpuvm expects BO > > > ranges to correspond 1:1 to virtual memory ranges that are mapped, and > > > does math on the BO offset accordingly. To make single page mappings > > > work, we need a way to turn off that math, keeping the BO offset always > > > constant and pointing to the same page (typically BO offset 0). > > > > > > To make this work, we need to handle all the corner cases when these > > > mappings intersect with regular mappings. The rules are simply to never > > > mix or merge a "regular" mapping with a single page mapping. > > > > > > drm_gpuvm has support for a flags field in drm_gpuva objects. This is > > > normally managed by drivers directly. We can introduce a > > > DRM_GPUVA_SINGLE_PAGE flag to handle this. However, to make it work, > > > sm_map and friends need to know ahead of time whether the new mapping is > > > a single page mapping or not. Therefore, we need to add an argument to > > > these functions so drivers can provide the flags to be filled into > > > drm_gpuva.flags. > > > > > > These changes should not affect any existing drivers that use drm_gpuvm > > > other than the API change: > > > > > > - imagination: Does not use flags at all > > > - nouveau: Only uses drm_gpuva_invalidate(), which is only called on > > > existing drm_gpuva objects (after the map steps) > > > - panthor: Does not use flags at all > > > - xe: Does not use drm_gpuva_init_from_op() or > > > drm_gpuva_remap()/drm_gpuva_map() (which call it). This means that the > > > flags field of the gpuva object is managed by the driver only, so these > > > changes cannot clobber it. > > > > > > Note that the way this is implemented, drm_gpuvm does not need to know > > > the GPU page size. It only has to never do math on the BO offset to meet > > > the requirements. > > > > > > I suspect that after this change there could be some cleanup possible in > > > the xe driver (which right now passes flags around in various > > > driver-specific ways from the map step through to drm_gpuva objects), > > > but I'll leave that to the Xe folks. > > > > > > Signed-off-by: Asahi Lina <lina@xxxxxxxxxxxxx> > > > --- > > > Asahi Lina (4): > > > drm/gpuvm: Add a flags argument to drm_gpuvm_sm_map[_*] > > > drm/gpuvm: Plumb through flags into drm_gpuva_op_map > > > drm/gpuvm: Add DRM_GPUVA_SINGLE_PAGE flag and logic > > > drm/gpuvm: Plumb through flags into drm_gpuva_init > > > > Without looking into any details yet: > > > > This is a bit of tricky one, since we're not even close to having a user for > > this new feature upstream yet, are we? > > Actually, we would be interesting in having this feature hooked up in > panthor. One use case we have is Vulkan sparse bindings, of course. But > we also have cases where we need to map a dummy page repeatedly on the > FW side. The approach we've been considering is slightly different: > pass a DRM_GPUVA_REPEAT_FLAG along with GEM range, so we can repeat a > range of the GEM (see the below diff, which is completely untested by > the way), but I think we'd be fine with this SINGLE_PAGE flag. Unless I've misunderstood the intent completely, it looks like Xe also wants something similar although they call it CPU_ADDR_MIRROR for some reason: https://lore.kernel.org/r/20250129195212.745731-9-matthew.brost@xxxxxxxxx Best regards, Liviu > > --->8--- > diff --git a/drivers/gpu/drm/drm_gpuvm.c b/drivers/gpu/drm/drm_gpuvm.c > index f9eb56f24bef..ea61f3ffaddf 100644 > --- a/drivers/gpu/drm/drm_gpuvm.c > +++ b/drivers/gpu/drm/drm_gpuvm.c > @@ -2053,16 +2053,17 @@ EXPORT_SYMBOL_GPL(drm_gpuva_unmap); > > static int > op_map_cb(const struct drm_gpuvm_ops *fn, void *priv, > - u64 addr, u64 range, > - struct drm_gem_object *obj, u64 offset) > + u64 addr, u64 va_range, > + struct drm_gem_object *obj, u64 offset, u64 gem_range) > { > struct drm_gpuva_op op = {}; > > op.op = DRM_GPUVA_OP_MAP; > op.map.va.addr = addr; > - op.map.va.range = range; > + op.map.va.range = va_range; > op.map.gem.obj = obj; > op.map.gem.offset = offset; > + op.map.gem.range = gem_range; > > return fn->sm_step_map(&op, priv); > } > @@ -2102,7 +2103,8 @@ static int > __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm, > const struct drm_gpuvm_ops *ops, void *priv, > u64 req_addr, u64 req_range, > - struct drm_gem_object *req_obj, u64 req_offset) > + struct drm_gem_object *req_obj, > + u64 req_offset, u64 req_gem_range) > { > struct drm_gpuva *va, *next; > u64 req_end = req_addr + req_range; > @@ -2237,7 +2239,7 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm, > > return op_map_cb(ops, priv, > req_addr, req_range, > - req_obj, req_offset); > + req_obj, req_offset, req_gem_range); > } > > static int > @@ -2344,10 +2346,43 @@ drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm, void *priv, > > return __drm_gpuvm_sm_map(gpuvm, ops, priv, > req_addr, req_range, > - req_obj, req_offset); > + req_obj, req_offset, 0); > } > EXPORT_SYMBOL_GPL(drm_gpuvm_sm_map); > > +/** > + * drm_gpuvm_sm_map_repeat() - repeatedly maps a GEM range over a VA range > + * @gpuvm: the &drm_gpuvm representing the GPU VA space > + * @priv: pointer to a driver private data structure > + * @req_addr: the start address of the new mapping > + * @req_range: the range of the new mapping > + * @req_obj: the &drm_gem_object to map > + * @req_offset: the offset within the &drm_gem_object > + * @req_gem_range: the offset within the &drm_gem_object > + * > + * Same as drm_gpuvm_sm_map() except it repeats a GEM range over a VA range > + * > + * Returns: 0 on success or a negative error code > + */ > +int > +drm_gpuvm_sm_map_repeat(struct drm_gpuvm *gpuvm, void *priv, > + u64 req_addr, u64 req_range, > + struct drm_gem_object *req_obj, > + u64 req_offset, u64 req_gem_range) > +{ > + const struct drm_gpuvm_ops *ops = gpuvm->ops; > + > + if (unlikely(!(ops && ops->sm_step_map && > + ops->sm_step_remap && > + ops->sm_step_unmap))) > + return -EINVAL; > + > + return __drm_gpuvm_sm_map(gpuvm, ops, priv, > + req_addr, req_range, > + req_obj, req_offset, req_gem_range); > +} > +EXPORT_SYMBOL_GPL(drm_gpuvm_sm_map_repeat); > + > /** > * drm_gpuvm_sm_unmap() - creates the &drm_gpuva_ops to split on unmap > * @gpuvm: the &drm_gpuvm representing the GPU VA space > @@ -2536,7 +2571,7 @@ drm_gpuvm_sm_map_ops_create(struct drm_gpuvm *gpuvm, > > ret = __drm_gpuvm_sm_map(gpuvm, &gpuvm_list_ops, &args, > req_addr, req_range, > - req_obj, req_offset); > + req_obj, req_offset, 0); > if (ret) > goto err_free_ops; > > diff --git a/include/drm/drm_gpuvm.h b/include/drm/drm_gpuvm.h > index 00d4e43b76b6..8157ede365d1 100644 > --- a/include/drm/drm_gpuvm.h > +++ b/include/drm/drm_gpuvm.h > @@ -846,6 +846,14 @@ struct drm_gpuva_op_map { > */ > u64 offset; > > + /** > + * @gem.range: the range of the GEM to map > + * > + * If smaller than va.range, the GEM range should be mapped > + * multiple times over the VA range. > + */ > + u64 range; > + > /** > * @gem.obj: the &drm_gem_object to map > */ > @@ -1203,6 +1211,11 @@ int drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm, void *priv, > u64 addr, u64 range, > struct drm_gem_object *obj, u64 offset); > > +int drm_gpuvm_sm_map_repeat(struct drm_gpuvm *gpuvm, void *priv, > + u64 addr, u64 range, > + struct drm_gem_object *obj, > + u64 offset, u64 gem_range); > + > int drm_gpuvm_sm_unmap(struct drm_gpuvm *gpuvm, void *priv, > u64 addr, u64 range); -- ==================== | I would like to | | fix the world, | | but they're not | | giving me the | \ source code! / --------------- ¯\_(ツ)_/¯
