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From: Robin Murphy <robin.murphy@arm.com>
To: Christoph Hellwig <hch@lst.de>, Jia He <justin.he@arm.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
	iommu@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] dma-mapping: fix dma_addressing_limited if dma_range_map can't cover all system RAM
Date: Tue, 10 Oct 2023 10:40:44 +0100	[thread overview]
Message-ID: <39d5aabd-4c09-4135-a3d7-00f6da7a1684@arm.com> (raw)
In-Reply-To: <20231010074816.GA9082@lst.de>

On 2023-10-10 08:48, Christoph Hellwig wrote:
> dma_addressing_limited is called for every dma (direct) map, and this
> new code is way to heavy for that.  We'll need to cache the information
> somehow.

But is it? That was my instinctive reaction as well, but AFAICS it is 
only actually used by drivers in setup paths, either directly or via 
dma_max_mapping_size(). The dma_capable() check which we *do* use for 
every actual mapping still just checks whether the given physical 
address exists in the range map. I believe the underlying problem here 
is when dma_capable() say the mapping needs bouncing, but then it's too 
big for that to succeed, since dma_max_mapping_size() gave the wrong 
answer to start with.

Thanks,
Robin.

  parent reply	other threads:[~2023-10-10  9:40 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-10  2:08 Jia He
2023-10-10  7:48 ` Christoph Hellwig
2023-10-10  8:42   ` Justin He
2023-10-10  9:40   ` Robin Murphy [this message]
2023-10-11  5:11     ` Christoph Hellwig
2023-10-16  2:59       ` Justin He

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