linux-kernel - Re: [PATCH] kernel: dma: let dma use vmalloc area

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: <20231127071430.GA28214@lst.de>
Date:   Mon, 27 Nov 2023 08:14:30 +0100
From:   Christoph Hellwig <hch@....de>
To:     "zhaoyang.huang" <zhaoyang.huang@...soc.com>
Cc:     Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org,
        Zhaoyang Huang <huangzhaoyang@...il.com>, steve.kang@...soc.com
Subject: Re: [PATCH] kernel: dma: let dma use vmalloc area

On Mon, Nov 27, 2023 at 11:09:30AM +0800, zhaoyang.huang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@...soc.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.