From nobody Fri Dec 19 07:35:56 2025 Received: from sender3-pp-f112.zoho.com (sender3-pp-f112.zoho.com [136.143.184.112]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A46F313AA31 for ; Wed, 26 Mar 2025 02:15:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.184.112 ARC-Seal: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742955340; cv=pass; b=Qr4jXVtkwboVUuDQS76hxhu5hDEUdYYSYORIHZs4SRhj2wiC8qcslVDn0zwXE4XEYSvV/5EQMN3gRIfn45z/QvFLfnAWULInq1gcisP8jIOBc8aJJH5ddWMNsWNBG6geaZPmFMLFm7dCQIQSG7zSkjlhgEkz3G0JJEsT5wAJQv0= ARC-Message-Signature: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742955340; c=relaxed/simple; bh=m9GD4loYkS9eoifl1EJQIY3WbQjjRF/a0URtsymk1mU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=l+6PiX52sDxdQWu/3lEpDScVIgcbhiYsUZ8ulTrM2uHnZjvyf65XD6KudO/lh6qIOL+lBRawLGr8P5LhG/GRI/6mbrSYn6wUEbEr+JNbU8WaUvbYBy/nmBxUt0NH4FSB5amkjAlw8tX63yckUtjobil1yTcIW8uVHpjWTGUkZs0= ARC-Authentication-Results: i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (1024-bit key) header.d=collabora.com header.i=adrian.larumbe@collabora.com header.b=VnTfUOjy; arc=pass smtp.client-ip=136.143.184.112 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=collabora.com header.i=adrian.larumbe@collabora.com header.b="VnTfUOjy" ARC-Seal: i=1; a=rsa-sha256; t=1742955319; cv=none; d=zohomail.com; s=zohoarc; b=buHt9+8wJ2ksc9/06QreSVQ1jLvLR69XLdNhzNlGH1n+VdbQzbuUWwwOvf0kZwVPmMEkhBkDBOJYSANDple11op8JHPd9zvpQw1hU1/6VLUQSSII7Y6yjwaGw//3PbGmafz0cU2iGFPBILRDFzSrV2pp5D35LIWt9hmkBeLAjnI= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1742955319; 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=eDDJBa43wl24zfW0m/nKztfofIyTDy2Iq6m6CG3HtAk=; b=QSMSm9uIWhwqtw6WdRYV6gjbqeUEtU8pc+ID24SdLiYl/uYPRyXbrjnAHxS1cWssNF+gXlf7JtOEkLdJkNmUnN5OvQL7o2ksPoqHPM5JoAWmvax/QesyvxeeCgxp9OTrvUu2NwMstgUGo/BkBj/z9qZo62uYYkovgz4Ps6S1Uzk= 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=1742955319; s=zohomail; d=collabora.com; i=adrian.larumbe@collabora.com; h=From:From:To:To:Cc:Cc:Subject:Subject:Date:Date:Message-ID:In-Reply-To:References:MIME-Version:Content-Type:Content-Transfer-Encoding:Message-Id:Reply-To; bh=eDDJBa43wl24zfW0m/nKztfofIyTDy2Iq6m6CG3HtAk=; b=VnTfUOjyyEJaAd4e+E2GUEG9Q8ZbsX/4wbg87KRRuZ7DnBZeq14dWpyF+w0oOv6d e0abxBxVT5cw7dyBjtIrJQHkJfv5QHxnnf8+rAZDN0kxOXGToZmgS3Q5OwirmEYqtc+ 8tSKQzxRTEJdHxEzzByVlpSav5+PJKS+15KaZbLE= Received: by mx.zohomail.com with SMTPS id 1742955317701794.8257212544316; Tue, 25 Mar 2025 19:15:17 -0700 (PDT) From: =?UTF-8?q?Adri=C3=A1n=20Larumbe?= To: Andrew Morton , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Boris Brezillon , Rob Herring , Steven Price , Liviu Dudau Cc: kernel@collabora.com, =?UTF-8?q?Adri=C3=A1n=20Larumbe?= , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org Subject: [RFC PATCH v2 2/6] drm/shmem: Introduce the notion of sparse objects Date: Wed, 26 Mar 2025 02:14:22 +0000 Message-ID: <20250326021433.772196-3-adrian.larumbe@collabora.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250326021433.772196-1-adrian.larumbe@collabora.com> References: <20250326021433.772196-1-adrian.larumbe@collabora.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Sparse DRM objects will store their backing pages in an xarray, to avoid the overhead of preallocating a huge struct page pointer array when only a very small range of indices might be assigned. For now, only the definition of a sparse object as a union alternative to a 'dense' object is provided, with functions that exploit it being part of later commits. Signed-off-by: Adri=C3=A1n Larumbe --- drivers/gpu/drm/drm_gem_shmem_helper.c | 68 +++++++++++++++++++++++++- include/drm/drm_gem_shmem_helper.h | 23 ++++++++- 2 files changed, 88 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_g= em_shmem_helper.c index d99dee67353a..5f75eb1230f6 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -128,6 +128,31 @@ struct drm_gem_shmem_object *drm_gem_shmem_create(stru= ct drm_device *dev, size_t } EXPORT_SYMBOL_GPL(drm_gem_shmem_create); =20 +/** + * drm_gem_shmem_create_sparse - Allocate a sparse object with the given s= ize + * @dev: DRM device + * @size: Size of the sparse object to allocate + * + * This function creates a sparse shmem GEM object. + * + * Returns: + * A struct drm_gem_shmem_object * on success or an ERR_PTR()-encoded nega= tive + * error code on failure. + */ +struct drm_gem_shmem_object *drm_gem_shmem_create_sparse(struct drm_device= *dev, size_t size) +{ + struct drm_gem_shmem_object *shmem =3D + __drm_gem_shmem_create(dev, size, false, NULL); + + if (!IS_ERR(shmem)) { + shmem->sparse =3D true; + xa_init_flags(&shmem->xapages, XA_FLAGS_ALLOC); + } + + return shmem; +} +EXPORT_SYMBOL_GPL(drm_gem_shmem_create_sparse); + /** * drm_gem_shmem_create_with_mnt - Allocate an object with the given size = in a * given mountpoint @@ -173,8 +198,8 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *sh= mem) sg_free_table(shmem->sgt); kfree(shmem->sgt); } - if (shmem->pages) - drm_gem_shmem_put_pages(shmem); + + drm_gem_shmem_put_pages(shmem); =20 drm_WARN_ON(obj->dev, shmem->pages_use_count); =20 @@ -196,6 +221,12 @@ static int drm_gem_shmem_get_pages(struct drm_gem_shme= m_object *shmem) if (shmem->pages_use_count++ > 0) return 0; =20 + /* We only allow increasing the user count in the case of + * sparse shmem objects with some backed pages for now + */ + if (shmem->sparse && xa_empty(&shmem->xapages)) + return -EINVAL; + pages =3D drm_gem_get_pages(obj); if (IS_ERR(pages)) { drm_dbg_kms(obj->dev, "Failed to get pages (%ld)\n", @@ -231,6 +262,14 @@ void drm_gem_shmem_put_pages(struct drm_gem_shmem_obje= ct *shmem) =20 dma_resv_assert_held(shmem->base.resv); =20 + if (!shmem->sparse) { + if (!shmem->pages) + return; + } else { + /* Not implemented yet */ + return; + } + if (drm_WARN_ON_ONCE(obj->dev, !shmem->pages_use_count)) return; =20 @@ -404,8 +443,15 @@ void drm_gem_shmem_vunmap(struct drm_gem_shmem_object = *shmem, { struct drm_gem_object *obj =3D &shmem->base; =20 + if (shmem->sparse) { + drm_err(obj->dev, "UM unmapping of sparse shmem objects not implemented\= n"); + return; + } + if (drm_gem_is_imported(obj)) { dma_buf_vunmap(obj->dma_buf, map); + } else if (obj->import_attach) { + dma_buf_vunmap(obj->import_attach->dmabuf, map); } else { dma_resv_assert_held(shmem->base.resv); =20 @@ -541,6 +587,12 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault = *vmf) struct page *page; pgoff_t page_offset; =20 + /* TODO: Implement UM mapping of sparse shmem objects */ + if (drm_WARN_ON(obj->dev, shmem->sparse)) { + drm_err(obj->dev, "UM mapping of sparse shmem objects not implemented\n"= ); + return VM_FAULT_SIGBUS; + } + /* We don't use vmf->pgoff since that has the fake offset */ page_offset =3D (vmf->address - vma->vm_start) >> PAGE_SHIFT; =20 @@ -566,8 +618,14 @@ static void drm_gem_shmem_vm_open(struct vm_area_struc= t *vma) struct drm_gem_object *obj =3D vma->vm_private_data; struct drm_gem_shmem_object *shmem =3D to_drm_gem_shmem_obj(obj); =20 + /* TODO: Implement UM mapping of sparse shmem objects */ + if (drm_WARN_ON(obj->dev, shmem->sparse)) + return; + drm_WARN_ON(obj->dev, drm_gem_is_imported(obj)); =20 + drm_WARN_ON(obj->dev, obj->import_attach); + dma_resv_lock(shmem->base.resv, NULL); =20 /* @@ -690,6 +748,9 @@ struct sg_table *drm_gem_shmem_get_sg_table(struct drm_= gem_shmem_object *shmem) { struct drm_gem_object *obj =3D &shmem->base; =20 + if (drm_WARN_ON(obj->dev, shmem->sparse)) + return ERR_PTR(-EINVAL); + drm_WARN_ON(obj->dev, drm_gem_is_imported(obj)); =20 return drm_prime_pages_to_sg(obj->dev, shmem->pages, obj->size >> PAGE_SH= IFT); @@ -702,6 +763,9 @@ static struct sg_table *drm_gem_shmem_get_pages_sgt_loc= ked(struct drm_gem_shmem_ int ret; struct sg_table *sgt; =20 + if (drm_WARN_ON(obj->dev, shmem->sparse)) + return ERR_PTR(-EINVAL); + if (shmem->sgt) return shmem->sgt; =20 diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem= _helper.h index cef5a6b5a4d6..00e47512b30f 100644 --- a/include/drm/drm_gem_shmem_helper.h +++ b/include/drm/drm_gem_shmem_helper.h @@ -6,6 +6,7 @@ #include #include #include +#include =20 #include #include @@ -29,7 +30,10 @@ struct drm_gem_shmem_object { /** * @pages: Page table */ - struct page **pages; + union { + struct page **pages; + struct xarray xapages; + }; =20 /** * @pages_use_count: @@ -91,12 +95,18 @@ struct drm_gem_shmem_object { * @map_wc: map object write-combined (instead of using shmem defaults). */ bool map_wc : 1; + + /** + * @sparse: the object is only partially backed by pages + */ + bool sparse : 1; }; =20 #define to_drm_gem_shmem_obj(obj) \ container_of(obj, struct drm_gem_shmem_object, base) =20 struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, = size_t size); +struct drm_gem_shmem_object *drm_gem_shmem_create_sparse(struct drm_device= *dev, size_t size); struct drm_gem_shmem_object *drm_gem_shmem_create_with_mnt(struct drm_devi= ce *dev, size_t size, struct vfsmount *gemfs); @@ -210,6 +220,10 @@ static inline struct sg_table *drm_gem_shmem_object_ge= t_sg_table(struct drm_gem_ { struct drm_gem_shmem_object *shmem =3D to_drm_gem_shmem_obj(obj); =20 + /* Use the specific sparse shmem get_sg_table function instead */ + if (WARN_ON(shmem->sparse)) + return ERR_PTR(-EINVAL); + return drm_gem_shmem_get_sg_table(shmem); } =20 @@ -229,6 +243,10 @@ static inline int drm_gem_shmem_object_vmap(struct drm= _gem_object *obj, { struct drm_gem_shmem_object *shmem =3D to_drm_gem_shmem_obj(obj); =20 + /* TODO: Implement kernel mapping of sparse shmem objects */ + if (WARN_ON(shmem->sparse)) + return -EACCES; + return drm_gem_shmem_vmap(shmem, map); } =20 @@ -263,6 +281,9 @@ static inline int drm_gem_shmem_object_mmap(struct drm_= gem_object *obj, struct v { struct drm_gem_shmem_object *shmem =3D to_drm_gem_shmem_obj(obj); =20 + if (shmem->sparse) + return -EACCES; + return drm_gem_shmem_mmap(shmem, vma); } =20 --=20 2.48.1