linux-kernel - Re: [PATCH -fixes] dma-mapping: add default implementation to arch_dma_{set|clear}

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Message-ID: <20240709111901.GC4421@lst.de>
Date: Tue, 9 Jul 2024 13:19:01 +0200
From: Christoph Hellwig <hch@....de>
To: Yangyu Chen <cyy@...self.name>
Cc: iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@....de>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Robin Murphy <robin.murphy@....com>
Subject: Re: [PATCH -fixes] dma-mapping: add default implementation to
 arch_dma_{set|clear}_uncached

On Tue, Jul 09, 2024 at 05:25:29PM +0800, Yangyu Chen wrote:
> Currently, we have some code in kernel/dma/direct.c which references
> arch_dma_set_uncached and arch_dma_clear_uncached. However, many
> architectures do not provide these symbols, and the code currently
> relies on compiler optimization to cut the unnecessary code. When the
> compiler fails to optimize it, the code will reference the symbol and
> cause a link error. I found this bug when developing some new extensions
> for RISC-V on LLVM. The error message is shown below:

Same comment as for the last one.  I think your compiler misbehaves,
and the typical reason for that would be if you disable all
optimizations.