On Mon Jul 7, 2025 at 7:04 PM CEST, Caterina Shablia wrote:
> diff --git a/drivers/gpu/drm/drm_gpuvm.c b/drivers/gpu/drm/drm_gpuvm.c
> index 05978c5c38b1..dc3c2f906400 100644
> --- a/drivers/gpu/drm/drm_gpuvm.c
> +++ b/drivers/gpu/drm/drm_gpuvm.c
> @@ -2098,12 +2098,48 @@ op_unmap_cb(const struct drm_gpuvm_ops *fn, void
> *priv,
> return fn->sm_step_unmap(&op, priv);
> }
>
> +static bool can_merge(struct drm_gpuvm *gpuvm, const struct drm_gpuva *a,
> + const struct drm_gpuva *b)
> +{
> + /* Only GEM-based mappings can be merged, and they must point to
> + * the same GEM object.
> + */
> + if (a->gem.obj != b->gem.obj || !a->gem.obj)
> + return false;
> +
> + /* Let's keep things simple for now and force all flags to match. */
> + if (a->flags != b->flags)
> + return false;
> +
> + /* Order VAs for the rest of the checks. */
> + if (a->va.addr > b->va.addr)
> + swap(a, b);
> +
> + /* We assume the caller already checked that VAs overlap or are
> + * contiguous.
> + */
> + if (drm_WARN_ON(gpuvm->drm, b->va.addr > a->va.addr + a->va.range))
> + return false;
> +
> + /* We intentionally ignore u64 underflows because all we care about
> + * here is whether the VA diff matches the GEM offset diff.
> + */
> + return b->va.addr - a->va.addr == b->gem.offset - a->gem.offset;
> +}
> +
> static int
> __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm,
> const struct drm_gpuvm_ops *ops, void *priv,
> const struct drm_gpuvm_map_req *req)
> {
> struct drm_gpuva *va, *next;
> + struct drm_gpuva reqva = {
> + .va.addr = req->va.addr,
> + .va.range = req->va.range,
> + .gem.offset = req->gem.offset,
> + .gem.obj = req->gem.obj,
> + .flags = req->flags,
Huh? Where does req->flags come from? I don't remember that this flag exists in
struct drm_gpuvm_map_req in the preceding patch?
> + };
> u64 req_end = req->va.addr + req->va.range;
> int ret;
>
> @@ -2116,12 +2152,9 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm,
> u64 addr = va->va.addr;
> u64 range = va->va.range;
> u64 end = addr + range;
> - bool merge = !!va->gem.obj;
> + bool merge = can_merge(gpuvm, va, &reqva);
I know you want to do the swap() trick above, but I don't like creating a
temporary struct drm_gpuva with all the other uninitialized fields.
If you really want this, can we please limit the scope? Maybe the following
helper:
static bool can_merge(struct drm_gpuvm *gpuvm,
const struct drm_gpuva *va,
struct drm_gpuvm_map_req *req)
{
struct drm_gpuva reqva = { ... };
return __can_merge(gpuvm, va, reqva);
}
