From nobody Thu Oct 2 19:24:05 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 518472F617E for ; Thu, 11 Sep 2025 23:02:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757631744; cv=none; b=IAKLQd3yQocZhsGNCWknFc1JKq6rsbepQGGYs7WCO2y/0u5yBbXWff4034eGaEpaPcThfbMmytchryoCsr/+ZnwLdAmAuYuqBfuq+BhpUFL1PNdnuI6linZa/aS5jMu6PbMQ/+Ln/KizXVAdlofdDUzkMMFclK+6exx/4kPB2uU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757631744; c=relaxed/simple; bh=zkb+msNpNOoGW826Z4j/D1GwFn1YWFvM+oLUjtAxGsk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=eEu0RFbbcQ98zPjuA9heGpb/TEoUdmWJ1mjtqhuzCe7GksJsh12dz4NySTtX65mkERsr7XS20Fzbsrrv12X9fgZ3VvUU0heqerLEAHojkDXFkjYR7hqd9VdGD8Tx85ajblrUkQUU/DhR8YlwjzWaW0wqmEwIlYDggFqtJrUNkUk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=KO9sHN/9; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="KO9sHN/9" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1757631742; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=xIN0/MhzULHsO+NOutgb84cZx03vcIUbF7Dq4BB0wAc=; b=KO9sHN/9RQbbHh+TrLAk5MkHYbFeAGqUBQFeriLbkTh2ZbjcAtB7RYaDD1wUv3IYX7enYO wZJRxIfqL7WFKht5BqcaSP3/BFT+QhqDa9c0gl6ONUumgyCjbEcq3tgNFwf3iRWyoOc2iP 9utAu464R+nP8eEyXj8Dna4RLjNhhDg= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-260-fb-PDMdBOBWUvQhtt4BQgQ-1; Thu, 11 Sep 2025 19:02:16 -0400 X-MC-Unique: fb-PDMdBOBWUvQhtt4BQgQ-1 X-Mimecast-MFC-AGG-ID: fb-PDMdBOBWUvQhtt4BQgQ_1757631733 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 25A5E180057B; Thu, 11 Sep 2025 23:02:13 +0000 (UTC) Received: from chopper.redhat.com (unknown [10.22.64.100]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 1493219432AE; Thu, 11 Sep 2025 23:02:08 +0000 (UTC) From: Lyude Paul To: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org Cc: Daniel Almeida , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich Subject: [PATCH v4 1/3] drm/gem/shmem: Extract drm_gem_shmem_init() from drm_gem_shmem_create() Date: Thu, 11 Sep 2025 18:57:38 -0400 Message-ID: <20250911230147.650077-2-lyude@redhat.com> In-Reply-To: <20250911230147.650077-1-lyude@redhat.com> References: <20250911230147.650077-1-lyude@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Content-Type: text/plain; charset="utf-8" With gem objects in rust, the most ideal way for us to be able to handle gem shmem object creation is to be able to handle the memory allocation of a gem object ourselves - and then have the DRM gem shmem helpers initialize the object we've allocated afterwards. So, let's spit out drm_gem_shmem_init() from drm_gem_shmem_create() to allow for doing this. Signed-off-by: Lyude Paul Reviewed-by: Daniel Almeida --- drivers/gpu/drm/drm_gem_shmem_helper.c | 75 +++++++++++++++++--------- include/drm/drm_gem_shmem_helper.h | 1 + 2 files changed, 51 insertions(+), 25 deletions(-) diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_g= em_shmem_helper.c index 5d1349c34afd3..b20a7b75c7228 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -48,28 +48,12 @@ static const struct drm_gem_object_funcs drm_gem_shmem_= funcs =3D { .vm_ops =3D &drm_gem_shmem_vm_ops, }; =20 -static struct drm_gem_shmem_object * -__drm_gem_shmem_create(struct drm_device *dev, size_t size, bool private, - struct vfsmount *gemfs) +static int __drm_gem_shmem_init(struct drm_device *dev, struct drm_gem_shm= em_object *shmem, + size_t size, bool private, struct vfsmount *gemfs) { - struct drm_gem_shmem_object *shmem; - struct drm_gem_object *obj; + struct drm_gem_object *obj =3D &shmem->base; int ret =3D 0; =20 - size =3D PAGE_ALIGN(size); - - if (dev->driver->gem_create_object) { - obj =3D dev->driver->gem_create_object(dev, size); - if (IS_ERR(obj)) - return ERR_CAST(obj); - shmem =3D to_drm_gem_shmem_obj(obj); - } else { - shmem =3D kzalloc(sizeof(*shmem), GFP_KERNEL); - if (!shmem) - return ERR_PTR(-ENOMEM); - obj =3D &shmem->base; - } - if (!obj->funcs) obj->funcs =3D &drm_gem_shmem_funcs; =20 @@ -81,7 +65,7 @@ __drm_gem_shmem_create(struct drm_device *dev, size_t siz= e, bool private, } if (ret) { drm_gem_private_object_fini(obj); - goto err_free; + return ret; } =20 ret =3D drm_gem_create_mmap_offset(obj); @@ -102,14 +86,55 @@ __drm_gem_shmem_create(struct drm_device *dev, size_t = size, bool private, __GFP_RETRY_MAYFAIL | __GFP_NOWARN); } =20 - return shmem; - + return 0; err_release: drm_gem_object_release(obj); -err_free: - kfree(obj); + return ret; +} =20 - return ERR_PTR(ret); +/** + * drm_gem_shmem_init - Initialize an allocated object. + * @dev: DRM device + * @obj: The allocated shmem GEM object. + * + * Returns: + * 0 on success, or a negative error code on failure. + */ +int drm_gem_shmem_init(struct drm_device *dev, struct drm_gem_shmem_object= *shmem, size_t size) +{ + return __drm_gem_shmem_init(dev, shmem, size, false, NULL); +} +EXPORT_SYMBOL_GPL(drm_gem_shmem_init); + +static struct drm_gem_shmem_object * +__drm_gem_shmem_create(struct drm_device *dev, size_t size, bool private, + struct vfsmount *gemfs) +{ + struct drm_gem_shmem_object *shmem; + struct drm_gem_object *obj; + int ret =3D 0; + + size =3D PAGE_ALIGN(size); + + if (dev->driver->gem_create_object) { + obj =3D dev->driver->gem_create_object(dev, size); + if (IS_ERR(obj)) + return ERR_CAST(obj); + shmem =3D to_drm_gem_shmem_obj(obj); + } else { + shmem =3D kzalloc(sizeof(*shmem), GFP_KERNEL); + if (!shmem) + return ERR_PTR(-ENOMEM); + obj =3D &shmem->base; + } + + ret =3D __drm_gem_shmem_init(dev, shmem, size, private, gemfs); + if (ret) { + kfree(obj); + return ERR_PTR(ret); + } + + return shmem; } /** * drm_gem_shmem_create - Allocate an object with the given size diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem= _helper.h index 92f5db84b9c22..235dc33127b9a 100644 --- a/include/drm/drm_gem_shmem_helper.h +++ b/include/drm/drm_gem_shmem_helper.h @@ -107,6 +107,7 @@ struct drm_gem_shmem_object { #define to_drm_gem_shmem_obj(obj) \ container_of(obj, struct drm_gem_shmem_object, base) =20 +int drm_gem_shmem_init(struct drm_device *dev, struct drm_gem_shmem_object= *shmem, size_t size); 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charset="utf-8" At the moment, the way that we currently free gem shmem objects is not ideal for rust bindings. drm_gem_shmem_free() releases all of the associated memory with a gem shmem object with kfree(), which means that for us to correctly release a gem shmem object in rust we have to manually drop all of the contents of our gem object structure in-place by hand before finally calling drm_gem_shmem_free() to release the shmem resources and the allocation for the gem object. Since the only reason this is an issue is because of drm_gem_shmem_free() calling kfree(), we can fix this by splitting drm_gem_shmem_free() out into itself and drm_gem_shmem_release(), where drm_gem_shmem_release() releases the various gem shmem resources without freeing the structure itself. With this, we can safely re-acquire the KBox for the gem object's memory allocation and let rust handle cleaning up all of the other struct members automatically. Signed-off-by: Lyude Paul Reviewed-by: Daniel Almeida --- V4: * Fix accidental word salad that made it into the commit message drivers/gpu/drm/drm_gem_shmem_helper.c | 23 ++++++++++++++++++----- include/drm/drm_gem_shmem_helper.h | 1 + 2 files changed, 19 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_g= em_shmem_helper.c index b20a7b75c7228..50594cf8e17cc 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -175,13 +175,13 @@ struct drm_gem_shmem_object *drm_gem_shmem_create_wit= h_mnt(struct drm_device *de EXPORT_SYMBOL_GPL(drm_gem_shmem_create_with_mnt); =20 /** - * drm_gem_shmem_free - Free resources associated with a shmem GEM object - * @shmem: shmem GEM object to free + * drm_gem_shmem_release - Release resources associated with a shmem GEM o= bject. + * @shmem: shmem GEM object * - * This function cleans up the GEM object state and frees the memory used = to - * store the object itself. + * This function cleans up the GEM object state, but does not free the mem= ory used to store the + * object itself. This function is meant to be a dedicated helper for the = Rust GEM bindings. */ -void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem) +void drm_gem_shmem_release(struct drm_gem_shmem_object *shmem) { struct drm_gem_object *obj =3D &shmem->base; =20 @@ -208,6 +208,19 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *s= hmem) } =20 drm_gem_object_release(obj); +} +EXPORT_SYMBOL_GPL(drm_gem_shmem_release); + +/** + * drm_gem_shmem_free - Free resources associated with a shmem GEM object + * @shmem: shmem GEM object to free + * + * This function cleans up the GEM object state and frees the memory used = to + * store the object itself. + */ +void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem) +{ + drm_gem_shmem_release(shmem); kfree(shmem); } EXPORT_SYMBOL_GPL(drm_gem_shmem_free); diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem= _helper.h index 235dc33127b9a..589f7bfe7506e 100644 --- a/include/drm/drm_gem_shmem_helper.h +++ b/include/drm/drm_gem_shmem_helper.h @@ -112,6 +112,7 @@ struct drm_gem_shmem_object *drm_gem_shmem_create(struc= t drm_device *dev, size_t struct drm_gem_shmem_object *drm_gem_shmem_create_with_mnt(struct drm_devi= ce *dev, size_t size, struct vfsmount *gemfs); 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Thu, 11 Sep 2025 23:02:25 +0000 (UTC) Received: from chopper.redhat.com (unknown [10.22.64.100]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 7B8E61944CCA; Thu, 11 Sep 2025 23:02:20 +0000 (UTC) From: Lyude Paul To: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org Cc: Daniel Almeida , Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Sumit Semwal , =?UTF-8?q?Christian=20K=C3=B6nig?= , Greg Kroah-Hartman , Viresh Kumar , Wedson Almeida Filho , Tamir Duberstein , Xiangfei Ding , linux-media@vger.kernel.org (open list:DMA BUFFER SHARING FRAMEWORK:Keyword:\bdma_(?:buf|fence|resv)\b), linaro-mm-sig@lists.linaro.org (moderated list:DMA BUFFER SHARING FRAMEWORK:Keyword:\bdma_(?:buf|fence|resv)\b) Subject: [PATCH v4 3/3] rust: Add dma_buf stub bindings Date: Thu, 11 Sep 2025 18:57:40 -0400 Message-ID: <20250911230147.650077-4-lyude@redhat.com> In-Reply-To: <20250911230147.650077-1-lyude@redhat.com> References: <20250911230147.650077-1-lyude@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Content-Type: text/plain; charset="utf-8" In order to implement the gem export callback, we need a type to represent struct dma_buf. So - this commit introduces a set of stub bindings for dma_buf. These bindings provide a ref-counted DmaBuf object, but don't currently implement any functionality for using the DmaBuf. Signed-off-by: Lyude Paul Reviewed-by: Daniel Almeida --- V3: * Rename as_ref() to from_raw() V4: * Add missing period to rustdoc at top of file rust/kernel/dma_buf.rs | 40 ++++++++++++++++++++++++++++++++++++++++ rust/kernel/lib.rs | 1 + 2 files changed, 41 insertions(+) create mode 100644 rust/kernel/dma_buf.rs diff --git a/rust/kernel/dma_buf.rs b/rust/kernel/dma_buf.rs new file mode 100644 index 0000000000000..50be3e4dd4098 --- /dev/null +++ b/rust/kernel/dma_buf.rs @@ -0,0 +1,40 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! DMA buffer API. +//! +//! C header: [`include/linux/dma-buf.h`](srctree/include/linux/dma-buf.h) + +use bindings; +use kernel::types::*; + +/// A DMA buffer object. +/// +/// # Invariants +/// +/// The data layout of this type is equivalent to that of `struct dma_buf`. +#[repr(transparent)] +pub struct DmaBuf(Opaque); + +// SAFETY: `struct dma_buf` is thread-safe +unsafe impl Send for DmaBuf {} +// SAFETY: `struct dma_buf` is thread-safe +unsafe impl Sync for DmaBuf {} + +#[expect(unused)] +impl DmaBuf { + /// Convert from a `*mut bindings::dma_buf` to a [`DmaBuf`]. + /// + /// # Safety + /// + /// The caller guarantees that `self_ptr` points to a valid initialize= d `struct dma_buf` for the + /// duration of the lifetime of `'a`, and promises to not violate rust= 's data aliasing rules + /// using the reference provided by this function. + pub(crate) unsafe fn from_raw<'a>(self_ptr: *mut bindings::dma_buf) ->= &'a Self { + // SAFETY: Our data layout is equivalent to `dma_buf` . + unsafe { &*self_ptr.cast() } + } + + pub(crate) fn as_raw(&self) -> *mut bindings::dma_buf { + self.0.get() + } +} diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index fcffc3988a903..59242d83efe21 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -81,6 +81,7 @@ pub mod device_id; pub mod devres; pub mod dma; +pub mod dma_buf; pub mod driver; #[cfg(CONFIG_DRM =3D "y")] pub mod drm; --=20 2.51.0