linux-kernel - Re: [PATCH 3/3] of: address: Use dma_default_coherent to determine default coherency

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] [day] [month] [year] [list]

Message-Id: <3E55E1F7-7A34-4165-9BF4-C2AAF6A6CFC1@flygoat.com>
Date:   Wed, 22 Feb 2023 17:57:44 +0000
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     Robin Murphy <robin.murphy@....com>
Cc:     "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        mpe@...erman.id.au, paul.walmsley@...ive.com, palmer@...belt.com,
        Rob Herring <robh+dt@...nel.org>,
        Christoph Hellwig <hch@....de>, m.szyprowski@...sung.com,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH 3/3] of: address: Use dma_default_coherent to determine
 default coherency



> 2023年2月22日 17:24，Robin Murphy <robin.murphy@....com> 写道：

[...]

> 
> AFAICS, all you should actually need is a single self-contained addition here, something like:
> 
> + /*
> +  * DT-based MIPS doesn't use OF_DMA_DEFAULT_COHERENT, but
> +  * might override the system-wide default at runtime.
> +  */
> +#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \
> + defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \
> + defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL)
> + is_coherent = dma_default_coherent;
> +#endif

That makes more sense, thanks.
I’ll append CONFIG_MIPS as a condition here as well because it may break RISC-V whose dma_default_coherent
is not set to true from very beginning.

> 
>>     node = of_node_get(np);
>>  
> 
> Then *after* that's fixed, we can do a more comprehensive refactoring to merge the two mechanisms properly. FWIW I think I'd prefer an approach closer to the first one, where config options control the initial value of dma_default_coherent rather than architectures having to override it unconditionally (and TBH I'd also like to have a generic config symbol for whether an arch supports per-device coherency or not).

Ok I’ll try to revert to the initial way.
Is there any reason that an arch can’t support per-device coherency?

Thanks
- Jiaxun


> 
> Thanks,
> Robin.