On Mon, 4 Dec 2023 18:33:00 +0100
Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx> wrote:
> +static int panthor_vm_prepare_unmap_op_ctx(struct panthor_vm_op_ctx *op_ctx,
> + struct panthor_vm *vm,
> + u64 va, u64 size)
> +{
> + u32 pt_count = 0;
> + int ret;
> +
> + memset(op_ctx, 0, sizeof(*op_ctx));
> + INIT_LIST_HEAD(&op_ctx->returned_vmas);
> + op_ctx->va.range = size;
> + op_ctx->va.addr = va;
> + op_ctx->flags = DRM_PANTHOR_VM_BIND_OP_TYPE_UNMAP;
> +
> + /* Pre-allocate L3 page tables to account for the split-2M-block
> + * situation on unmap.
> + */
> + if (va != ALIGN(va, SZ_2M))
> + pt_count++;
> +
> + if (va + size != ALIGN(va + size, SZ_2M) &&
> + ALIGN(va + size, SZ_2M) != ALIGN(va, SZ_2M))
> + pt_count++;
> +
> + if (pt_count) {
> + op_ctx->rsvd_page_tables.pages = kcalloc(pt_count,
> + sizeof(*op_ctx->rsvd_page_tables.pages),
> + GFP_KERNEL);
> + if (!op_ctx->rsvd_page_tables.pages)
> + goto err_cleanup;
> +
> + ret = kmem_cache_alloc_bulk(pt_cache, GFP_KERNEL, pt_count,
> + op_ctx->rsvd_page_tables.pages);
> + if (ret != pt_count) {
> + ret = -ENOMEM;
> + goto err_cleanup;
> + }
> + op_ctx->rsvd_page_tables.count = pt_count;
> + }
We also need to allocate {prev,next}_vma objects, because partial
unmaps will call sm_step_remap(), which leads to a NULL deref if we
don't pre-allocate these objects. I'm reworking the code to have a
3-entry array of preallocated VMAs instead of having
->map.{prev,new,next}_vma fields. We can then populate this array when
preparing an op_ctx, and pick from this preallocated pool in
sm_step_[re]map().
> +
> + return 0;
> +
> +err_cleanup:
> + panthor_vm_cleanup_op_ctx(op_ctx, vm);
> + return ret;
> +}
