linux-kernel - Re: [PATCH v12 2/3] rust: add dma coherent allocator abstraction.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <80f31377-f897-4881-b294-87f13f75acd4@gmail.com>
Date: Tue, 4 Mar 2025 10:58:56 +0200
From: Abdiel Janulgue <abdiel.janulgue@...il.com>
To: Andreas Hindborg <a.hindborg@...nel.org>
Cc: aliceryhl@...gle.com, dakr@...nel.org, robin.murphy@....com,
 daniel.almeida@...labora.com, rust-for-linux@...r.kernel.org,
 Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
 Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>,
 Benno Lossin <benno.lossin@...ton.me>, Trevor Gross <tmgross@...ch.edu>,
 Valentin Obst <kernel@...entinobst.de>, linux-kernel@...r.kernel.org,
 Christoph Hellwig <hch@....de>, Marek Szyprowski <m.szyprowski@...sung.com>,
 airlied@...hat.com, iommu@...ts.linux.dev
Subject: Re: [PATCH v12 2/3] rust: add dma coherent allocator abstraction.



On 03/03/2025 13:30, Andreas Hindborg wrote:
> "Abdiel Janulgue" <abdiel.janulgue@...il.com> writes:
> 
>> 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.
>>
>> Nacked-by: Christoph Hellwig <hch@....de>
>> Signed-off-by: Abdiel Janulgue <abdiel.janulgue@...il.com>
> [...]
> 
>> diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
>> index 0640b7e115be..8f3808c8b7fe 100644
>> --- a/rust/helpers/helpers.c
>> +++ b/rust/helpers/helpers.c
>> @@ -13,6 +13,7 @@
>>   #include "build_bug.c"
>>   #include "cred.c"
>>   #include "device.c"
>> +#include "dma.c"
>>   #include "err.c"
>>   #include "fs.c"
>>   #include "io.c"
>> diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs
>> new file mode 100644
>> index 000000000000..b4dd5d411711
>> --- /dev/null
>> +++ b/rust/kernel/dma.rs
>> @@ -0,0 +1,421 @@
>> +// 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,
>> +    transmute::{AsBytes, FromBytes},
>> +    types::ARef,
>> +};
>> +
>> +/// Inform the kernel about the device's DMA addressing capabilities. This will set the mask for
>> +/// both streaming and coherent APIs together.
>> +pub fn dma_set_mask_and_coherent(dev: &Device, mask: u64) -> i32 {
>> +    // SAFETY: device pointer is guaranteed as valid by invariant on `Device`.
>> +    unsafe { bindings::dma_set_mask_and_coherent(dev.as_raw(), mask) }
>> +}
>> +
>> +/// Same as `dma_set_mask_and_coherent`, but set the mask only for streaming mappings.
>> +pub fn dma_set_mask(dev: &Device, mask: u64) -> i32 {
>> +    // SAFETY: device pointer is guaranteed as valid by invariant on `Device`.
>> +    unsafe { bindings::dma_set_mask(dev.as_raw(), mask) }
>> +}
> 
> I'm rebasing some of the dma pool code I'm using for NVMe on top of
> these patches, and I notice that these methods in the original code from
> way back (besides being on Device) has these methods return `Result`:
> 
>      pub fn dma_set_mask(&self, mask: u64) -> Result {
>          let dev = self.as_raw();
>          let ret = unsafe { bindings::dma_set_mask(dev as _, mask) };
>          if ret != 0 {
>              Err(Error::from_errno(ret))
>          } else {
>              Ok(())
>          }
>      }
> 
> Is there a reason for not returning a `Result` in this series?
> 

Hi Andreas, the original dma_set_mask function got lost to me for some 
reason. But yes, this is indeed a better approach!

Regards,
Abdiel