From: Christoph Hellwig <hch@lst.de>
To: "Dr. David Alan Gilbert" <dave@treblig.org>
Cc: iommu@lists.linux.dev, mchehab@kernel.org, hch@lst.de,
linux-media@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: Regression: v4l/bttv vbi vs iommu
Date: Thu, 2 Feb 2023 11:09:26 +0100 [thread overview]
Message-ID: <20230202100926.GA14931@lst.de> (raw)
In-Reply-To: <Y9qSwkLxeMpffZK/@gallifrey>
On Wed, Feb 01, 2023 at 04:26:42PM +0000, Dr. David Alan Gilbert wrote:
> f5ff79fddf0efecca538046b5cc20fb3ded2ec4f is the first bad commit
> commit f5ff79fddf0efecca538046b5cc20fb3ded2ec4f
> Author: Christoph Hellwig <hch@lst.de>
> Date: Sat Feb 26 16:40:21 2022 +0100
>
> dma-mapping: remove CONFIG_DMA_REMAP
Which just enabled some code on common x86 configs that was already
used on many other platforms. In other words: the code already
was buggy, but got away with it on x86 so far as no one tested on
e.g. arm or arm64.
The bug is in videobuf_dma_init_kernel:
for (i = 0; i < nr_pages; i++) {
void *addr;
addr = dma_alloc_coherent(dma->dev, PAGE_SIZE,
&(dma->dma_addr[i]), GFP_KERNEL);
if (addr == NULL)
goto out_free_pages;
dma->vaddr_pages[i] = virt_to_page(addr);
}
dma->vaddr = vmap(dma->vaddr_pages, nr_pages, VM_MAP | VM_IOREMAP,
PAGE_KERNEL);
The address by dma_alloc_coherent is just a kernel virtual address,
and virt_to_page must not be used on it as it could be vmalloc (as in
this case) or various other really odd forms of memory.
next prev parent reply other threads:[~2023-02-02 10:09 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-01 16:26 Regression: v4l/bttv vbi vs iommu Dr. David Alan Gilbert
2023-02-01 20:48 ` Hans Verkuil
2023-02-02 3:04 ` Dr. David Alan Gilbert
2023-02-03 6:35 ` Christoph Hellwig
2023-02-03 8:05 ` Hans Verkuil
2023-08-13 13:14 ` Dr. David Alan Gilbert
2023-08-13 13:44 ` Hans Verkuil
2023-11-11 19:57 ` Dr. David Alan Gilbert
2023-11-13 14:38 ` Hans Verkuil
2023-11-14 0:31 ` Dr. David Alan Gilbert
2023-02-02 10:09 ` Christoph Hellwig [this message]
2023-02-02 17:09 ` Dr. David Alan Gilbert
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