From: Christoph Hellwig <hch@lst.de>
To: "zhaoyang.huang" <zhaoyang.huang@unisoc.com>
Cc: Christoph Hellwig <hch@lst.de>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Robin Murphy <robin.murphy@arm.com>,
iommu@lists.linux.dev, linux-kernel@vger.kernel.org,
Zhaoyang Huang <huangzhaoyang@gmail.com>,
steve.kang@unisoc.com
Subject: Re: [PATCH] kernel: dma: let dma use vmalloc area
Date: Mon, 27 Nov 2023 08:14:30 +0100 [thread overview]
Message-ID: <20231127071430.GA28214@lst.de> (raw)
In-Reply-To: <20231127030930.1074374-1-zhaoyang.huang@unisoc.com>
On Mon, Nov 27, 2023 at 11:09:30AM +0800, zhaoyang.huang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
>
> memremap within dma_init_coherent_memory will map the given phys_addr
> into vmalloc area if the pa is not found during iterating iomem_resources,
> which conflict the rejection of vmalloc area in dma_map_single_attrs.
I can't parse this sentence.
> IMO, it is find to let all valid virtual address be valid for DMA as the
> user will keep corresponding RAM safe for transfer.
No, vmalloc address can't be passed to map_single. You need to pass
the page to dma_map_page, and explicitly mange cache consistency
using the invalidate_kernel_vmap_range and flush_kernel_vmap_range
helpers.
next prev parent reply other threads:[~2023-11-27 7:14 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-27 3:09 [PATCH] kernel: dma: let dma use vmalloc area zhaoyang.huang
2023-11-27 3:29 ` Zhaoyang Huang
2023-11-27 7:14 ` Christoph Hellwig [this message]
2023-11-27 8:56 ` Zhaoyang Huang
2023-11-27 9:32 ` Christoph Hellwig
2023-11-27 11:24 ` Robin Murphy
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