From mboxrd@z Thu Jan 1 00:00:00 1970 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 941BA1A8F6E; Wed, 4 Dec 2024 19:09:05 +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=1733339347; cv=pass; b=jZXBax4OhDll4a8CcqvrXYhckQ7PacU8X+De71j9lhzKKlkZap3N0jAeb3P739tVp0ot4Ug506Ho3xJncKicTdMnampEnH6sUBJgVPIdNXH0zNYygxP08UNH59VZfzTGalEKo2+CtUSvAULWjd8ILJ8vyhMo0WMbRNXTkUhYzzk= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733339347; c=relaxed/simple; bh=8yMQMBPDNh7miLRJnVQ+GZCLHZmaTJO7LvPRqau3VA8=; h=Content-Type:Mime-Version:Subject:From:In-Reply-To:Date:Cc: Message-Id:References:To; b=Ia8OymeyaBCN4gCMj6VnaFPnwrD/c/RxRIzARdNfaVvo6XIUJYW1/bNAGCtfLgA/k9qTwUqngdoZsm0cpKKD/hjBhy3KB8rtoDtOAHz355eMkzNShX7WtuLd8YV1gOmF7ndeVxwZhXD0NeC0LTg0bp2tDRa5onDsxaaB4q0FGZY= 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=daniel.almeida@collabora.com header.b=TLNFfKkO; 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=daniel.almeida@collabora.com header.b="TLNFfKkO" ARC-Seal: i=1; a=rsa-sha256; t=1733339316; cv=none; d=zohomail.com; s=zohoarc; b=QsSWQZI/TvaddnoXx/MYb/9Lh/wmef6H30BcfUk1BaAuiMf3EKczYuJEMNBKcdObZH7EaopEkKtJl4uv/JDFqk5+gzcQrcMqD4SXrA32tpHHnEoPPfq93dpcc6FOZfNNIxFCeo0P/BCpSfY4H/VFlDMOU4Wl6xhhJ4A2OUGev6A= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1733339316; 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=O+vCOyKaol/q4vjTgIGLLkHXjDioz2gyMQBKcVMwTn0=; b=IFv0tnYmovacfX0cjSwxNbI1oJFGSxw30nR7pXnDWDsVf3L6pGaFU6Fj5tR29sSNPB4cuwUbkUj2GsKMN7VkLmMLtd/7l73S3VexF/r6sjF6cr9EfgJ5l98iVOyBsQwS/hGm/v3ihcZPHj0awMoSjG/2dRiznUdJBvKd47LioXE= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=collabora.com; spf=pass smtp.mailfrom=daniel.almeida@collabora.com; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1733339316; s=zohomail; d=collabora.com; i=daniel.almeida@collabora.com; h=Content-Type:Mime-Version:Subject:Subject:From:From:In-Reply-To:Date:Date:Cc:Cc:Content-Transfer-Encoding:Message-Id:Message-Id:References:To:To:Reply-To; bh=O+vCOyKaol/q4vjTgIGLLkHXjDioz2gyMQBKcVMwTn0=; b=TLNFfKkO6XnS08DURZN9tgTLEAwOtGt9iyVshW+8QYt6m1o7g8hNrPsD6fWL3M2f d+h8KcW05RxuxXHNvoK1b56vJKNKUss7SAxj+D7Qd5xwt0hvK0HJlngTOv5zPQlMysj ycCoo9eCZoo3ZeqI+o+V7hvHXbN0ZjevZq9kByPA= Received: by mx.zohomail.com with SMTPS id 173333931476854.75299437249271; Wed, 4 Dec 2024 11:08:34 -0800 (PST) Content-Type: text/plain; charset=utf-8 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3826.200.121\)) Subject: Re: [PATCH v5 2/2] rust: add dma coherent allocator abstraction. From: Daniel Almeida In-Reply-To: <20241203170752.1834271-3-abdiel.janulgue@gmail.com> Date: Wed, 4 Dec 2024 16:08:18 -0300 Cc: rust-for-linux@vger.kernel.org, Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?utf-8?Q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Wedson Almeida Filho , Valentin Obst , open list , Christoph Hellwig , Marek Szyprowski , Robin Murphy , airlied@redhat.com, "open list:DMA MAPPING HELPERS" Content-Transfer-Encoding: quoted-printable Message-Id: References: <20241203170752.1834271-1-abdiel.janulgue@gmail.com> <20241203170752.1834271-3-abdiel.janulgue@gmail.com> To: Abdiel Janulgue X-Mailer: Apple Mail (2.3826.200.121) X-ZohoMailClient: External Hi Abdiel, > On 3 Dec 2024, at 14:07, Abdiel Janulgue = wrote: >=20 > Add a simple dma coherent allocator rust abstraction. Based on > Andreas Hindborg's dma abstractions from the rnvme driver, which > was also based on earlier work by Wedson Almeida Filho. >=20 > Signed-off-by: Abdiel Janulgue > --- > rust/bindings/bindings_helper.h | 1 + > rust/kernel/dma.rs | 136 ++++++++++++++++++++++++++++++++ > rust/kernel/lib.rs | 1 + > 3 files changed, 138 insertions(+) > create mode 100644 rust/kernel/dma.rs >=20 > diff --git a/rust/bindings/bindings_helper.h = b/rust/bindings/bindings_helper.h > index 5c4dfe22f41a..49bf713b9bb6 100644 > --- a/rust/bindings/bindings_helper.h > +++ b/rust/bindings/bindings_helper.h > @@ -11,6 +11,7 @@ > #include > #include > #include > +#include > #include > #include > #include > diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs > new file mode 100644 > index 000000000000..9279be235fcf > --- /dev/null > +++ b/rust/kernel/dma.rs > @@ -0,0 +1,136 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +//! Direct memory access (DMA). > +//! > +//! C header: = [`include/linux/dma-mapping.h`](srctree/include/linux/dma-mapping.h) > + > +use crate::{ > + bindings, > + build_assert, > + device::Device, > + error::code::*, > + error::Result, > + types::ARef, > + transmute::{AsBytes, FromBytes}, > +}; > + > +/// An abstraction of the `dma_alloc_coherent` API. > +/// > +/// This is an abstraction around the `dma_alloc_coherent` API which = is used to allocate and map > +/// large consistent DMA regions. > +/// > +/// A [`CoherentAllocation`] instance contains a pointer to the = allocated region (in the > +/// processor's virtual address space) and the device address which = can be given to the device > +/// as the DMA address base of the region. The region is released = once [`CoherentAllocation`] > +/// is dropped. > +/// > +/// # Invariants > +/// > +/// For the lifetime of an instance of [`CoherentAllocation`], the = cpu address is a valid pointer > +/// to an allocated region of consistent memory and we hold a = reference to the device. > +pub struct CoherentAllocation { > + dev: ARef, > + dma_handle: bindings::dma_addr_t, > + count: usize, > + cpu_addr: *mut T, > +} > + > +impl CoherentAllocation { > + /// Allocates a region of `size_of:: * count` of consistent = memory. > + /// > + /// # Examples > + /// > + /// ``` > + /// use kernel::device::Device; > + /// use kernel::dma::CoherentAllocation; > + /// > + /// # fn test(dev: &Device) -> Result { > + /// let c: CoherentAllocation =3D = CoherentAllocation::alloc_coherent(dev, 4, GFP_KERNEL)?; > + /// # Ok::<(), Error>(()) } > + /// ``` > + pub fn alloc_coherent( > + dev: &Device, > + count: usize, > + flags: kernel::alloc::Flags, > + ) -> Result> { > + build_assert!(core::mem::size_of::() > 0, > + "It doesn't make sense for the allocated type = to be a ZST"); > + > + let size =3D = count.checked_mul(core::mem::size_of::()).ok_or(EOVERFLOW)?; > + let mut dma_handle =3D 0; > + // SAFETY: device pointer is guaranteed as valid by invariant = on `Device`. > + // We ensure that we catch the failure on this function and = throw an ENOMEM > + let ret =3D unsafe { > + bindings::dma_alloc_attrs( > + dev.as_raw(), > + size, > + &mut dma_handle, flags.as_raw(), > + 0, > + ) > + }; > + if ret.is_null() { > + return Err(ENOMEM) > + } > + // INVARIANT: We just successfully allocated a coherent = region which is accessible for > + // `count` elements, hence the cpu address is valid. We also = hold a refcounted reference > + // to the device. > + Ok(Self { > + dev: dev.into(), > + dma_handle, > + count, > + cpu_addr: ret as *mut T, > + }) > + } > + > + /// Returns the base address to the allocated region and the dma = handle. The caller takes > + /// ownership of the returned resources. > + pub fn into_parts(self) -> (usize, bindings::dma_addr_t) { > + let ret =3D (self.cpu_addr as _, self.dma_handle); > + core::mem::forget(self); > + ret > + } > + > + /// Returns the base address to the allocated region in the CPU's = virtual address space. > + pub fn start_ptr(&self) -> *const T { > + self.cpu_addr as _ > + } > + > + /// Returns the base address to the allocated region in the CPU's = virtual address space as > + /// a mutable pointer. > + pub fn start_ptr_mut(&mut self) -> *mut T { > + self.cpu_addr > + } > + > + /// Returns a DMA handle which may given to the device as the DMA = address base of > + /// the region. > + pub fn dma_handle(&self) -> bindings::dma_addr_t { > + self.dma_handle > + } > + > + /// Returns the CPU-addressable region as a slice. > + pub fn cpu_buf<'a>(&self) -> &'a [T] Why this =E2=80=98a here? Lifetime elision rules should tie the lifetime = of the returned slice to the lifetime of &self automatically > + { > + // SAFETY: The pointer is valid due to type invariant on = `CoherentAllocation` and > + // is valid for reads for `self.count * size_of::` bytes. > + unsafe { core::slice::from_raw_parts(self.cpu_addr, = self.count) } > + } > + > + /// Performs the same functionality as `cpu_buf`, except that a = mutable slice is returned. > + pub fn cpu_buf_mut<'a>(&mut self) -> &'a mut [T] Same here > + { > + // SAFETY: The pointer is valid due to type invariant on = `CoherentAllocation` and > + // is valid for reads for `self.count * size_of::` bytes. > + unsafe { core::slice::from_raw_parts_mut(self.cpu_addr, = self.count) } > + } > +} > + > +impl Drop for CoherentAllocation { > + fn drop(&mut self) { > + let size =3D self.count * core::mem::size_of::(); > + // SAFETY: the device, cpu address, and the dma handle is = valid due to the > + // type invariants on `CoherentAllocation`. > + unsafe { bindings::dma_free_attrs(self.dev.as_raw(), size, > + self.cpu_addr as _, > + self.dma_handle, 0) } > + } > +} > diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs > index e1065a7551a3..6e90ebf5a130 100644 > --- a/rust/kernel/lib.rs > +++ b/rust/kernel/lib.rs > @@ -35,6 +35,7 @@ > mod build_assert; > pub mod cred; > pub mod device; > +pub mod dma; > pub mod error; > #[cfg(CONFIG_RUST_FW_LOADER_ABSTRACTIONS)] > pub mod firmware; > --=20 > 2.43.0 >=20 >=20 By the way, I tested this using a slightly modified version of the = sample Rust platform driver from Danilo=E2=80=99s v3 submission. It=E2=80=99s working as intended :) With the change above, you can add: Reviewed-by: Daniel Almeida Tested-by: Daniel Almeida =E2=80=94 Daniel