From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 15D70F94CB3 for ; Tue, 21 Apr 2026 21:44:38 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 7758C10EDCF; Tue, 21 Apr 2026 21:44:37 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (1024-bit key; unprotected) header.d=collabora.com header.i=adrian.larumbe@collabora.com header.b="El2yZryj"; dkim-atps=neutral Received: from sender4-pp-f112.zoho.com (sender4-pp-f112.zoho.com [136.143.188.112]) by gabe.freedesktop.org (Postfix) with ESMTPS id 6E09610EDC5 for ; Tue, 21 Apr 2026 21:44:36 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; t=1776807863; cv=none; d=zohomail.com; s=zohoarc; b=VvHXW+cC8x76Dmc2EmcqnZ4SFGHwvekvd2LPZqO+m4Qdn1ulPNgNqyPPJwuNw/iMGZ/Nu5O4UaNXvcsbmUhFIWNoLYNIjzB8GPEkgdO4ZtOf2bQIlF1+hUtbrX6fqcE8ib2v7syD6uZs3PzknzdgJj+9DanofGUrP4dPiAMmG64= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1776807863; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:Subject:To:To:Message-Id:Reply-To; bh=0kzwpxrJVObYPgg65A9SdreimOlhgw/OF2S/SRwAEaw=; b=mDk5WTuyRO7nPUvm6/KX9OEW1rFGcC0MxtvOAVKXJTBe+pptBf68Q9Zlqg6gEzvFBDaeyWtXjOQT3aJaIrM+T1qotv8vqeMmieXPY0Bb2azNYtajNClOhPNVNn+CKjk9Xdi3JrEwO9gfL7gxm80fF/1xgOfLkW3MJQ2mptwXlUM= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=collabora.com; spf=pass smtp.mailfrom=adrian.larumbe@collabora.com; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1776807863; s=zohomail; d=collabora.com; i=adrian.larumbe@collabora.com; h=Date:Date:From:From:To:To:Cc:Cc:Subject:Subject:Message-ID:References:MIME-Version:Content-Type:Content-Transfer-Encoding:In-Reply-To:Message-Id:Reply-To; bh=0kzwpxrJVObYPgg65A9SdreimOlhgw/OF2S/SRwAEaw=; b=El2yZryjHK4h69x7ZOtlMj/35u0me9mRnrKCS95F4nLA/cewlPnPNx/ouk2y6Tvl KMFn7fLpylUBBzDNRQsKytpbsQ33z/Y9gFnYph+2w0m9giYAOxtJbMtAQELlbUm8bt8 Pz6FkgDH7IyCjarWzSUPRoZJiK+cze6n13w/VWrI= Received: by mx.zohomail.com with SMTPS id 1776807862338322.49908759339144; Tue, 21 Apr 2026 14:44:22 -0700 (PDT) Date: Tue, 21 Apr 2026 22:44:18 +0100 From: =?utf-8?Q?Adri=C3=A1n?= Larumbe To: Boris Brezillon Cc: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Steven Price , kernel@collabora.com, Liviu Dudau , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Daniel Almeida , Alice Ryhl Subject: Re: [PATCH v8 5/6] drm/panthor: Support sparse mappings Message-ID: References: <20260416214453.112332-1-adrian.larumbe@collabora.com> <20260416214453.112332-6-adrian.larumbe@collabora.com> <20260417104023.19d5e83e@fedora> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260417104023.19d5e83e@fedora> X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 17.04.2026 10:40, Boris Brezillon wrote: > On Thu, 16 Apr 2026 22:43:51 +0100 > Adrián Larumbe wrote: > > > Allow UM to bind sparsely populated memory regions by cyclically mapping > > virtual ranges over a kernel-allocated dummy BO. This alternative is > > preferable to the old method of handling sparseness in the UMD, because it > > relied on the creation of a buffer object to the same end, despite the fact > > Vulkan sparse resources don't need to be backed by a driver BO. > > > > The choice of backing sparsely-bound regions with a Panhtor BO was made so > > as to profit from the existing shrinker reclaim code. That way no special > > treatment must be given to the dummy sparse BOs when reclaiming memory, as > > would be the case if we had chosen a raw kernel page implementation. > > > > A new dummy BO is allocated per open file context, because even though the > > Vulkan spec mandates that writes into sparsely bound regions must be > > discarded, our implementation is still a workaround over the fact Mali CSF > > GPUs cannot support this behaviour on the hardware level, so writes still > > make it into the backing BO. If we had a global one, then it could be a > > venue for information leaks between file contexts, which should never > > happen in DRM. > > > > Signed-off-by: Adrián Larumbe > > Just a few minor things, but it looks good overall. Once addressed, > this is > > Reviewed-by: Boris Brezillon > > > --- > > drivers/gpu/drm/panthor/panthor_gem.c | 18 +++ > > drivers/gpu/drm/panthor/panthor_gem.h | 2 + > > drivers/gpu/drm/panthor/panthor_mmu.c | 160 ++++++++++++++++++++++---- > > include/uapi/drm/panthor_drm.h | 12 ++ > > 4 files changed, 170 insertions(+), 22 deletions(-) > > > > diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c > > index 69cef05b6ef7..833153c2b080 100644 > > --- a/drivers/gpu/drm/panthor/panthor_gem.c > > +++ b/drivers/gpu/drm/panthor/panthor_gem.c > > @@ -1345,6 +1345,24 @@ panthor_kernel_bo_create(struct panthor_device *ptdev, struct panthor_vm *vm, > > return ERR_PTR(ret); > > } > > > > +/** > > + * panthor_dummy_bo_create() - Create a Panthor BO meant to back sparse bindings. > > + * @ptdev: Device. > > + * > > + * Return: A valid pointer in case of success, an ERR_PTR() otherwise. > > + */ > > +struct panthor_gem_object * > > +panthor_dummy_bo_create(struct panthor_device *ptdev) > > +{ > > + /* Since even when the DRM device's mount point has enabled THP we have no guarantee > > + * that drm_gem_get_pages() will return a single 2MiB PMD, and also we cannot be sure > > + * that the 2MiB won't be reclaimed and re-allocated later on as 4KiB chunks, it doesn't > > + * make sense to pre-populate this object's page array, nor to fall back on a BO size > > + * of 4KiB. Sticking to a dummy object size of 2MiB lets us keep things simple for now. > > + */ > > + return panthor_gem_create(&ptdev->base, SZ_2M, DRM_PANTHOR_BO_NO_MMAP, NULL, 0); > > +} > > + > > static bool can_swap(void) > > { > > return get_nr_swap_pages() > 0; > > diff --git a/drivers/gpu/drm/panthor/panthor_gem.h b/drivers/gpu/drm/panthor/panthor_gem.h > > index ae0491d0b121..8639c2fa08e6 100644 > > --- a/drivers/gpu/drm/panthor/panthor_gem.h > > +++ b/drivers/gpu/drm/panthor/panthor_gem.h > > @@ -315,6 +315,8 @@ panthor_kernel_bo_create(struct panthor_device *ptdev, struct panthor_vm *vm, > > > > void panthor_kernel_bo_destroy(struct panthor_kernel_bo *bo); > > > > +struct panthor_gem_object *panthor_dummy_bo_create(struct panthor_device *ptdev); > > + > > #ifdef CONFIG_DEBUG_FS > > void panthor_gem_debugfs_init(struct drm_minor *minor); > > #endif > > diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c > > index 54f7f7a8d44f..8b4470d4bf85 100644 > > --- a/drivers/gpu/drm/panthor/panthor_mmu.c > > +++ b/drivers/gpu/drm/panthor/panthor_mmu.c > > @@ -112,6 +112,18 @@ struct panthor_mmu { > > struct panthor_vm_pool { > > /** @xa: Array used for VM handle tracking. */ > > struct xarray xa; > > + > > + /** > > + * @dummy: Dummy object used for sparse mappings > > + * > > + * Sparse bindings map virtual address ranges onto a dummy > > + * BO in a modulo fashion. Even though sparse writes are meant > > + * to be discarded and reads undefined, writes are still reflected > > + * in the dummy buffer. That means we must keep a dummy object per > > + * file context, to avoid data leaks between them. > > + * > > nit: drop the extra blank line. > > > + */ > > + struct panthor_gem_object *dummy; > > }; > > > > /** > > @@ -391,6 +403,16 @@ struct panthor_vm { > > */ > > struct list_head lru_node; > > } reclaim; > > + > > + /** > > + * @dummy: Dummy object used for sparse mappings. > > + * > > + * VM's must keep a reference to the file context-wide dummy BO because > > + * they can outlive the file context, which includes the VM pool holding > > + * the original dummy BO reference. > > + * > > + */ > > + struct panthor_gem_object *dummy; > > }; > > > > /** > > @@ -1020,6 +1042,45 @@ panthor_vm_map_pages(struct panthor_vm *vm, u64 iova, int prot, > > return 0; > > } > > > > +static int > > +panthor_vm_map_sparse(struct panthor_vm *vm, u64 iova, int prot, > > + struct sg_table *sgt, u64 size) > > +{ > > + u64 start_iova = iova; > > + int ret; > > + > > + if (iova & (SZ_2M - 1)) { > > + u64 unaligned_size = min(ALIGN(iova, SZ_2M) - iova, size); > > + > > + ret = panthor_vm_map_pages(vm, iova, prot, sgt, > > + 0, unaligned_size); > > + if (ret) > > + return ret; > > + > > + size -= unaligned_size; > > + iova += unaligned_size; > > + } > > + > > + /* TODO: we should probably optimize this at the io_pgtable level. */ > > + while (size > 0) { > > + u64 next_size = min(size, sg_dma_len(sgt->sgl)); > > + > > + ret = panthor_vm_map_pages(vm, iova, prot, > > + sgt, 0, next_size); > > + if (ret) > > + goto err_unmap; > > + > > + size -= next_size; > > + iova += next_size; > > + } > > + > > + return 0; > > + > > +err_unmap: > > + panthor_vm_unmap_pages(vm, start_iova, iova - start_iova); > > + return ret; > > +} > > + > > static int flags_to_prot(u32 flags) > > { > > int prot = 0; > > @@ -1262,6 +1323,7 @@ static int panthor_vm_op_ctx_prealloc_pts(struct panthor_vm_op_ctx *op_ctx) > > (DRM_PANTHOR_VM_BIND_OP_MAP_READONLY | \ > > DRM_PANTHOR_VM_BIND_OP_MAP_NOEXEC | \ > > DRM_PANTHOR_VM_BIND_OP_MAP_UNCACHED | \ > > + DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE | \ > > DRM_PANTHOR_VM_BIND_OP_TYPE_MASK) > > > > static int panthor_vm_prepare_map_op_ctx(struct panthor_vm_op_ctx *op_ctx, > > @@ -1269,6 +1331,7 @@ static int panthor_vm_prepare_map_op_ctx(struct panthor_vm_op_ctx *op_ctx, > > struct panthor_gem_object *bo, > > const struct drm_panthor_vm_bind_op *op) > > { > > + bool is_sparse = op->flags & DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE; > > struct drm_gpuvm_bo *preallocated_vm_bo; > > struct sg_table *sgt = NULL; > > int ret; > > @@ -1277,11 +1340,14 @@ static int panthor_vm_prepare_map_op_ctx(struct panthor_vm_op_ctx *op_ctx, > > return -EINVAL; > > > > if ((op->flags & ~PANTHOR_VM_BIND_OP_MAP_FLAGS) || > > - (op->flags & DRM_PANTHOR_VM_BIND_OP_TYPE_MASK) != DRM_PANTHOR_VM_BIND_OP_TYPE_MAP) > > + (op->flags & DRM_PANTHOR_VM_BIND_OP_TYPE_MASK) != DRM_PANTHOR_VM_BIND_OP_TYPE_MAP || > > + (is_sparse && !(op->flags & DRM_PANTHOR_VM_BIND_OP_MAP_NOEXEC))) > > Can we move that to a separate if (), maybe with a comment explaining > why. > > > return -EINVAL; > > > > /* Make sure the VA and size are in-bounds. */ > > - if (op->size > bo->base.size || op->bo_offset > bo->base.size - op->size) > > + if (!is_sparse && (op->size > bo->base.size || op->bo_offset > bo->base.size - op->size)) > > + return -EINVAL; > > + else if (is_sparse && (op->bo_handle || op->bo_offset)) > > return -EINVAL; > > I would just make it a separate if() and let the compile optimize it. > > /* For non-sparse, make sure the VA and size are in-bounds. > * For sparse, this is not applicable, because the dummy BO is > * repeatedly mapped over a potentially wider VA range. > */ > if (!is_sparse && (op->size > bo->base.size || op->bo_offset > bo->base.size - op->size)) > return -EINVAL; > > /* For sparse, we don't expect any user BO, the BO we get passed > * is the dummy BO attached to the VM pool. > */ > if (is_sparse && (op->bo_handle || op->bo_offset)) > return -EINVAL; > > > > > /* If the BO has an exclusive VM attached, it can't be mapped to other VMs. */ > > @@ -1543,6 +1609,9 @@ int panthor_vm_pool_create_vm(struct panthor_device *ptdev, > > return ret; > > } > > > > + drm_gem_object_get(&pool->dummy->base); > > + vm->dummy = pool->dummy; > > + > > args->user_va_range = kernel_va_start; > > return id; > > } > > @@ -1634,6 +1703,7 @@ void panthor_vm_pool_destroy(struct panthor_file *pfile) > > xa_for_each(&pfile->vms->xa, i, vm) > > panthor_vm_destroy(vm); > > > > + drm_gem_object_put(&pfile->vms->dummy->base); > > xa_destroy(&pfile->vms->xa); > > kfree(pfile->vms); > > } > > @@ -1651,6 +1721,11 @@ int panthor_vm_pool_create(struct panthor_file *pfile) > > return -ENOMEM; > > > > xa_init_flags(&pfile->vms->xa, XA_FLAGS_ALLOC1); > > + > > + pfile->vms->dummy = panthor_dummy_bo_create(pfile->ptdev); > > + if (IS_ERR(pfile->vms->dummy)) > > + return PTR_ERR(pfile->vms->dummy); > > + > > return 0; > > } > > > > @@ -1968,6 +2043,9 @@ static void panthor_vm_free(struct drm_gpuvm *gpuvm) > > > > free_io_pgtable_ops(vm->pgtbl_ops); > > > > + if (vm->dummy) > > + drm_gem_object_put(&vm->dummy->base); > > + > > drm_mm_takedown(&vm->mm); > > kfree(vm); > > } > > @@ -2127,7 +2205,23 @@ static void panthor_vma_init(struct panthor_vma *vma, u32 flags) > > #define PANTHOR_VM_MAP_FLAGS \ > > (DRM_PANTHOR_VM_BIND_OP_MAP_READONLY | \ > > DRM_PANTHOR_VM_BIND_OP_MAP_NOEXEC | \ > > - DRM_PANTHOR_VM_BIND_OP_MAP_UNCACHED) > > + DRM_PANTHOR_VM_BIND_OP_MAP_UNCACHED | \ > > + DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE) > > + > > +static int > > +panthor_vm_exec_map_op(struct panthor_vm *vm, u32 flags, > > + const struct drm_gpuva_op_map *op) > > +{ > > + struct panthor_gem_object *bo = to_panthor_bo(op->gem.obj); > > + int prot = flags_to_prot(flags); > > + > > + if (flags & DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE) > > + return panthor_vm_map_sparse(vm, op->va.addr, prot, > > + bo->dmap.sgt, op->va.range); > > + > > + return panthor_vm_map_pages(vm, op->va.addr, prot, bo->dmap.sgt, > > + op->gem.offset, op->va.range); > > +} > > > > static int panthor_gpuva_sm_step_map(struct drm_gpuva_op *op, void *priv) > > { > > @@ -2141,9 +2235,7 @@ static int panthor_gpuva_sm_step_map(struct drm_gpuva_op *op, void *priv) > > > > panthor_vma_init(vma, op_ctx->flags & PANTHOR_VM_MAP_FLAGS); > > > > - ret = panthor_vm_map_pages(vm, op->map.va.addr, flags_to_prot(vma->flags), > > - op_ctx->map.bo->dmap.sgt, op->map.gem.offset, > > - op->map.va.range); > > + ret = panthor_vm_exec_map_op(vm, vma->flags, &op->map); > > if (ret) { > > panthor_vm_op_ctx_return_vma(op_ctx, vma); > > return ret; > > @@ -2159,13 +2251,13 @@ static int panthor_gpuva_sm_step_map(struct drm_gpuva_op *op, void *priv) > > } > > > > static bool > > -iova_mapped_as_huge_page(struct drm_gpuva_op_map *op, u64 addr) > > +iova_mapped_as_huge_page(struct drm_gpuva_op_map *op, u64 addr, bool is_sparse) > > { > > struct panthor_gem_object *bo = to_panthor_bo(op->gem.obj); > > const struct page *pg; > > pgoff_t bo_offset; > > > > Maybe add a comment here explaining why zero is picked for sparse mappings > (the dummy BO is 2M, so checking if the first page is 2M large is enough). > > > - bo_offset = addr - op->va.addr + op->gem.offset; > > + bo_offset = !is_sparse ? addr - op->va.addr + op->gem.offset : 0; > > pg = bo->backing.pages[bo_offset >> PAGE_SHIFT]; > > > > return folio_size(page_folio(pg)) >= SZ_2M; > > @@ -2175,6 +2267,8 @@ static void > > unmap_hugepage_align(const struct drm_gpuva_op_remap *op, > > u64 *unmap_start, u64 *unmap_range) > > { > > + struct panthor_vma *unmap_vma = container_of(op->unmap->va, struct panthor_vma, base); > > + bool is_sparse = unmap_vma->flags & DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE; > > u64 aligned_unmap_start, aligned_unmap_end, unmap_end; > > > > unmap_end = *unmap_start + *unmap_range; > > @@ -2186,7 +2280,7 @@ unmap_hugepage_align(const struct drm_gpuva_op_remap *op, > > */ > > if (op->prev && aligned_unmap_start < *unmap_start && > > op->prev->va.addr <= aligned_unmap_start && > > - iova_mapped_as_huge_page(op->prev, *unmap_start)) { > > + (iova_mapped_as_huge_page(op->prev, *unmap_start, is_sparse))) { > > *unmap_range += *unmap_start - aligned_unmap_start; > > *unmap_start = aligned_unmap_start; > > } > > @@ -2196,7 +2290,7 @@ unmap_hugepage_align(const struct drm_gpuva_op_remap *op, > > */ > > if (op->next && aligned_unmap_end > unmap_end && > > op->next->va.addr + op->next->va.range >= aligned_unmap_end && > > - iova_mapped_as_huge_page(op->next, unmap_end - 1)) { > > + (iova_mapped_as_huge_page(op->next, *unmap_start, is_sparse))) { > > *unmap_range += aligned_unmap_end - unmap_end; > > } > > } > > @@ -2231,15 +2325,27 @@ static int panthor_gpuva_sm_step_remap(struct drm_gpuva_op *op, > > panthor_vm_unmap_pages(vm, unmap_start, unmap_range); > > } > > > > + /* In the following two branches, neither remap::unmap::offset nor remap::unmap::keep > > + * can be trusted to contain legitimate values in the case of sparse mappings, because > > + * the drm_gpuvm core calculates them on the assumption that a VM_BIND operation's > > + * range is always less than the target BO. That doesn't hold in the case of sparse > > + * bindings, but we don't care to adjust the BO offset of new VA's spawned by a remap > > + * operation because we ignore them altogether when sparse-mapping pages on a HW level > > + * just further below. If we ever wanted to make use of remap::unmap::keep, then this > > + * logic would have to be reworked. > > + */ > > if (op->remap.prev) { > > - struct panthor_gem_object *bo = to_panthor_bo(op->remap.prev->gem.obj); > > u64 offset = op->remap.prev->gem.offset + unmap_start - op->remap.prev->va.addr; > > u64 size = op->remap.prev->va.addr + op->remap.prev->va.range - unmap_start; > > + const struct drm_gpuva_op_map map_op = { > > + .va.addr = unmap_start, > > + .va.range = size, > > + .gem.obj = op->remap.prev->gem.obj, > > + .gem.offset = offset, > > + }; > > > > - if (!unmap_vma->evicted) { > > - ret = panthor_vm_map_pages(vm, unmap_start, > > - flags_to_prot(unmap_vma->flags), > > - bo->dmap.sgt, offset, size); > > + if (!unmap_vma->evicted && size > 0) { > > + ret = panthor_vm_exec_map_op(vm, unmap_vma->flags, &map_op); > > if (ret) > > return ret; > > } > > @@ -2250,14 +2356,17 @@ static int panthor_gpuva_sm_step_remap(struct drm_gpuva_op *op, > > } > > > > if (op->remap.next) { > > - struct panthor_gem_object *bo = to_panthor_bo(op->remap.next->gem.obj); > > u64 addr = op->remap.next->va.addr; > > u64 size = unmap_start + unmap_range - op->remap.next->va.addr; > > + const struct drm_gpuva_op_map map_op = { > > + .va.addr = addr, > > + .va.range = size, > > + .gem.obj = op->remap.next->gem.obj, > > + .gem.offset = op->remap.next->gem.offset, > > + }; > > > > - if (!unmap_vma->evicted) { > > - ret = panthor_vm_map_pages(vm, addr, flags_to_prot(unmap_vma->flags), > > - bo->dmap.sgt, op->remap.next->gem.offset, > > - size); > > + if (!unmap_vma->evicted && size > 0) { > > + ret = panthor_vm_exec_map_op(vm, unmap_vma->flags, &map_op); > > if (ret) > > return ret; > > } > > @@ -2817,11 +2926,15 @@ panthor_vm_bind_prepare_op_ctx(struct drm_file *file, > > > > switch (op->flags & DRM_PANTHOR_VM_BIND_OP_TYPE_MASK) { > > case DRM_PANTHOR_VM_BIND_OP_TYPE_MAP: > > - gem = drm_gem_object_lookup(file, op->bo_handle); > > + if (!(op->flags & DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE)) > > + gem = drm_gem_object_lookup(file, op->bo_handle); > > + else > > + gem = &vm->dummy->base; > > nit: blank line here. > > Also, how about we do a > > gem = drm_gem_object_get(&vm->dummy->base) I'm afraid drm_gem_object_get() doesn't return a pointer to the same object. Other drivers work around this by defining their own refcnt macro like: static inline struct xe_bo *xe_bo_get(struct xe_bo *bo) { if (bo) drm_gem_object_get(&bo->ttm.base); return bo; } However, this is meant to operate on the driver-specific bo rather than a generic DRM one. We could also do this: if (!(op->flags & DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE)) gem = drm_gem_object_lookup(file, op->bo_handle); else drm_gem_object_get(gem = &vm->dummy->base); although I think this is usually frowned upon, but I've noticed 'checkpatch.pl --strict' doesn't report it. > here so we can unconditionally call drm_gem_object_put() after > panthor_vm_prepare_map_op_ctx(), like we did so far. > > > ret = panthor_vm_prepare_map_op_ctx(op_ctx, vm, > > gem ? to_panthor_bo(gem) : NULL, > > op); > > - drm_gem_object_put(gem); > > + if (!(op->flags & DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE)) > > + drm_gem_object_put(gem); > > nit: blank line here. > > > return ret; > > > > case DRM_PANTHOR_VM_BIND_OP_TYPE_UNMAP: > > @@ -3025,6 +3138,9 @@ int panthor_vm_map_bo_range(struct panthor_vm *vm, struct panthor_gem_object *bo > > struct panthor_vm_op_ctx op_ctx; > > int ret; > > > > + if (drm_WARN_ON(&vm->ptdev->base, flags & DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE)) > > + return -EINVAL; > > + > > ret = panthor_vm_prepare_map_op_ctx(&op_ctx, vm, bo, &op); > > if (ret) > > return ret; > > diff --git a/include/uapi/drm/panthor_drm.h b/include/uapi/drm/panthor_drm.h > > index 42c901ebdb7a..1490a2223766 100644 > > --- a/include/uapi/drm/panthor_drm.h > > +++ b/include/uapi/drm/panthor_drm.h > > @@ -614,6 +614,18 @@ enum drm_panthor_vm_bind_op_flags { > > */ > > DRM_PANTHOR_VM_BIND_OP_MAP_UNCACHED = 1 << 2, > > > > + /** > > + * @DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE: Sparsely map a virtual memory range > > + * > > + * Only valid with DRM_PANTHOR_VM_BIND_OP_TYPE_MAP. > > + * > > + * When this flag is set, the whole vm_bind range is mapped over a dummy object in a cyclic > > + * fashion, and all GPU reads from addresses in the range return undefined values. This flag > > + * being set means drm_panthor_vm_bind_op:offset and drm_panthor_vm_bind_op::handle must > > + * both be set to 0. DRM_PANTHOR_VM_BIND_OP_MAP_NOEXEC must also be set. > > + */ > > + DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE = 1 << 3, > > + > > /** > > * @DRM_PANTHOR_VM_BIND_OP_TYPE_MASK: Mask used to determine the type of operation. > > */ Adrian Larumbe