From nobody Tue Feb 10 00:00:20 2026 Received: from sender4-pp-f112.zoho.com (sender4-pp-f112.zoho.com [136.143.188.112]) (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 628A91DE2B3 for ; Tue, 18 Feb 2025 23:29:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.188.112 ARC-Seal: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739921359; cv=pass; b=tA3d2Wy0es15a/b1J9009qE5RnkTrnWxv+wYLNImdk5l5J5nxA/LQQ0KBM8kNTZzmgkCSer6HCRB4tc6La/29dyBi4PoOwf2w///CHvDW+aUgnznhs35aSfYpo4gfqwKL85Mv+GZPNK86HbeEQMHhk3mPhTunRCfMYu21n0nlU0= ARC-Message-Signature: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739921359; c=relaxed/simple; bh=i0FZfSuI/Yogq5ZsgNJT9DTD0EEseJKrkDj2sfB+ECc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=a+rDApF6wjjKsD7gKP2b3oUnWsiaQYxSFnT+htP2+NRLgM1XVGQOrZxXPyp7ornd5lhHuiCA7ax4MOJ7JjB/2D9wGIibJ0m40v2eL79o2FlMHvmJFyDmqK74N9KIE1NHtnv858ht3dMePJrKZJn9kNWf/HcbmNZYIgjiaCgVTic= 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=M2r2mMvi; arc=pass smtp.client-ip=136.143.188.112 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="M2r2mMvi" ARC-Seal: i=1; a=rsa-sha256; t=1739921340; cv=none; d=zohomail.com; s=zohoarc; b=RnCgSv/BfIU54AQTpHckROhV7AhgvZ2s5yE1hiYtY4HI7OCmRj3pgWpm9HbVTvp9MZ84V6hJJfXKvForuQ3i+q4wX+ssJm+mXzGG88sPn5/AYr84mJDF8NwzJWxPZUfbPjCM/+7MA1Rpw/aDaD3zPM4uqk1kXgOFrd2yv1zELiE= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1739921340; 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=n3MGcvZJ2jssBxw31RXxSN0eBDZxEkdm3sXeyoWiJR4=; b=lGA4gdInt0uvqni3N8MDyjGAYMCuR3KXVnl7XRj1tXZqc5Mx/90xMmmQchkfQED960y0qecQL6MKsrkPt5d9aFfU12xg47H+fqm4KJ9xkw3MPTUhGU5YeSmU+JywQXPb7Dt47ZDvH22NXtDMQXaNNHgv9UMhtL7kEs0K+KsF3Sw= 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=1739921340; 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=n3MGcvZJ2jssBxw31RXxSN0eBDZxEkdm3sXeyoWiJR4=; b=M2r2mMviKC8pmuNGhWoKa6o3u99Kcp1TEkCLHqjdKKOgdX2x2VgEWzAFBXICR3Ep yOBNJMWCw1kbO14NcMuLcmP68AKt0KHww1jhaUIMZpD5t+Dd2M2ZTe2Ly7s24+5pReW kCsQCIMAqIIFOFFO0vMcbAswrIady1ubXJUsU8hA= Received: by mx.zohomail.com with SMTPS id 1739921339255606.5607224644493; Tue, 18 Feb 2025 15:28:59 -0800 (PST) From: =?UTF-8?q?Adri=C3=A1n=20Larumbe?= To: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Boris Brezillon , Steven Price , Rob Herring , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter Cc: kernel@collabora.com, =?UTF-8?q?Adri=C3=A1n=20Larumbe?= Subject: [RFC PATCH 4/7] drm/shmem: Introduce the notion of sparse objects Date: Tue, 18 Feb 2025 23:25:34 +0000 Message-ID: <20250218232552.3450939-5-adrian.larumbe@collabora.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250218232552.3450939-1-adrian.larumbe@collabora.com> References: <20250218232552.3450939-1-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 la= ter commits. Signed-off-by: Adri=C3=A1n Larumbe --- drivers/gpu/drm/drm_gem_shmem_helper.c | 42 +++++++++++++++++++++++--- include/drm/drm_gem_shmem_helper.h | 18 ++++++++++- 2 files changed, 54 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_g= em_shmem_helper.c index 5ab351409312..d63e42be2d72 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -10,6 +10,7 @@ #include #include #include +#include =20 #ifdef CONFIG_X86 #include @@ -50,7 +51,7 @@ static const struct drm_gem_object_funcs drm_gem_shmem_fu= ncs =3D { =20 static struct drm_gem_shmem_object * __drm_gem_shmem_create(struct drm_device *dev, size_t size, bool private, - struct vfsmount *gemfs) + bool sparse, struct vfsmount *gemfs) { struct drm_gem_shmem_object *shmem; struct drm_gem_object *obj; @@ -90,6 +91,11 @@ __drm_gem_shmem_create(struct drm_device *dev, size_t si= ze, bool private, =20 INIT_LIST_HEAD(&shmem->madv_list); =20 + if (unlikely(sparse)) + xa_init_flags(&shmem->xapages, XA_FLAGS_ALLOC); + + shmem->sparse =3D sparse; + if (!private) { /* * Our buffers are kept pinned, so allocating them @@ -124,10 +130,16 @@ __drm_gem_shmem_create(struct drm_device *dev, size_t= size, bool private, */ struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, = size_t size) { - return __drm_gem_shmem_create(dev, size, false, NULL); + return __drm_gem_shmem_create(dev, size, false, false, NULL); } EXPORT_SYMBOL_GPL(drm_gem_shmem_create); =20 +struct drm_gem_shmem_object *drm_gem_shmem_create_sparse(struct drm_device= *dev, size_t size) +{ + return __drm_gem_shmem_create(dev, size, false, true, NULL); +} +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 @@ -145,7 +157,7 @@ struct drm_gem_shmem_object *drm_gem_shmem_create_with_= mnt(struct drm_device *de size_t size, struct vfsmount *gemfs) { - return __drm_gem_shmem_create(dev, size, false, gemfs); + return __drm_gem_shmem_create(dev, size, false, false, gemfs); } EXPORT_SYMBOL_GPL(drm_gem_shmem_create_with_mnt); =20 @@ -173,7 +185,9 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *sh= mem) sg_free_table(shmem->sgt); kfree(shmem->sgt); } - if (shmem->pages) + + if ((!shmem->sparse && shmem->pages) || + (shmem->sparse && !xa_empty(&shmem->xapages))) drm_gem_shmem_put_pages(shmem); =20 drm_WARN_ON(obj->dev, shmem->pages_use_count); @@ -191,11 +205,19 @@ static int drm_gem_shmem_get_pages(struct drm_gem_shm= em_object *shmem) struct drm_gem_object *obj =3D &shmem->base; struct page **pages; =20 + if (drm_WARN_ON(obj->dev, shmem->sparse)) + return -EINVAL; + dma_resv_assert_held(shmem->base.resv); =20 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", @@ -541,6 +563,8 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *= vmf) struct page *page; pgoff_t page_offset; =20 + drm_WARN_ON(obj->dev, shmem->sparse); + /* We don't use vmf->pgoff since that has the fake offset */ page_offset =3D (vmf->address - vma->vm_start) >> PAGE_SHIFT; =20 @@ -567,6 +591,7 @@ static void drm_gem_shmem_vm_open(struct vm_area_struct= *vma) struct drm_gem_shmem_object *shmem =3D to_drm_gem_shmem_obj(obj); =20 drm_WARN_ON(obj->dev, obj->import_attach); + drm_WARN_ON(obj->dev, shmem->sparse); =20 dma_resv_lock(shmem->base.resv, NULL); =20 @@ -666,6 +691,9 @@ void drm_gem_shmem_print_info(const struct drm_gem_shme= m_object *shmem, if (shmem->base.import_attach) return; =20 + if (drm_WARN_ON(shmem->base.dev, shmem->sparse)) + return; + drm_printf_indent(p, indent, "pages_use_count=3D%u\n", shmem->pages_use_c= ount); drm_printf_indent(p, indent, "vmap_use_count=3D%u\n", shmem->vmap_use_cou= nt); drm_printf_indent(p, indent, "vaddr=3D%p\n", shmem->vaddr); @@ -691,6 +719,7 @@ struct sg_table *drm_gem_shmem_get_sg_table(struct drm_= gem_shmem_object *shmem) struct drm_gem_object *obj =3D &shmem->base; =20 drm_WARN_ON(obj->dev, obj->import_attach); + drm_WARN_ON(obj->dev, shmem->sparse); =20 return drm_prime_pages_to_sg(obj->dev, shmem->pages, obj->size >> PAGE_SH= IFT); } @@ -702,6 +731,9 @@ 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 @@ -787,7 +819,7 @@ drm_gem_shmem_prime_import_sg_table(struct drm_device *= dev, size_t size =3D PAGE_ALIGN(attach->dmabuf->size); struct drm_gem_shmem_object *shmem; =20 - shmem =3D __drm_gem_shmem_create(dev, size, true, NULL); + shmem =3D __drm_gem_shmem_create(dev, size, true, false, NULL); if (IS_ERR(shmem)) return ERR_CAST(shmem); =20 diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem= _helper.h index d22e3fb53631..902039cfc4ce 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 +30,11 @@ struct drm_gem_shmem_object { /** * @pages: Page table */ - struct page **pages; + union { + + struct page **pages; + struct xarray xapages; + }; =20 /** * @pages_use_count: @@ -91,6 +96,11 @@ struct drm_gem_shmem_object { * @map_wc: map object write-combined (instead of using shmem defaults). */ bool map_wc : 1; + + /** + * @sparse: the object's virtual memory space is only partially backed by= pages + */ + bool sparse : 1; }; =20 #define to_drm_gem_shmem_obj(obj) \ @@ -229,6 +239,9 @@ 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 + if (shmem->sparse) + return -EACCES; + return drm_gem_shmem_vmap(shmem, map); } =20 @@ -263,6 +276,9 @@ 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 2.47.1