From: Christoph Hellwig <hch@infradead.org>
To: Sinan Kaya <okaya@codeaurora.org>
Cc: Christoph Hellwig <hch@infradead.org>,
linux-rdma@vger.kernel.org, timur@codeaurora.org,
cov@codeaurora.org, Yishai Hadas <yishaih@mellanox.com>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH V2] net: ethernet: mellanox: correct page conversion
Date: Mon, 18 Apr 2016 06:59:36 -0700 [thread overview]
Message-ID: <20160418135936.GA25909@infradead.org> (raw)
In-Reply-To: <5714E5D6.7050600@codeaurora.org>
On Mon, Apr 18, 2016 at 09:49:10AM -0400, Sinan Kaya wrote:
> Here is a good description of logical address vs. virtual address.
>
> https://www.quora.com/What-is-the-Kernel-logical-and-virtual-addresses-What-is-the-difference-between-them-What-is-the-type-of-addresses-listed-in-the-System-map
That's not how we use the terms in Linux. But it's not really the point
of my question either.
> > Is this correct?
> >
> No, the driver is plain broken without this patch. It causes a kernel panic
> during driver probe.
>
> This is the definition of vmap API.
>
> https://www.kernel.org/doc/htmldocs/kernel-api/API-vmap.html
Thanks for the pointer, but I'm actually the person who introduced vmap
to Linux a long time ago, and this is once again not my question.
> You cannot take several virtually mapped addresses returned by dma_alloc_coherent
> and try to make them virtually contiguous again.
But now we're getting closer to the issue: the mlx4_en driver is using
vmap on buffers allocated using dma_alloc_coherent if on a 64-bit
architecture, and that's obviously broken.
Now the big quetions is: why does it do that, given that
dma_alloc_coherent can be used for high order allocations anyway (and in
fact many architectures implement is using a version of vmap).
Let's get some answers on these question from the Mellanox folks and
work from there.
next prev parent reply other threads:[~2016-04-18 13:59 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-16 22:23 [PATCH V2] net: ethernet: mellanox: correct page conversion Sinan Kaya
2016-04-18 4:00 ` David Miller
2016-04-18 5:06 ` okaya
2016-04-18 15:59 ` David Miller
2016-04-18 16:06 ` Sinan Kaya
2016-04-18 6:54 ` Eli Cohen
2016-04-18 13:53 ` Sinan Kaya
2016-04-18 14:05 ` Eli Cohen
2016-04-18 14:32 ` Christoph Hellwig
2016-04-18 14:39 ` Eli Cohen
2016-04-18 15:17 ` Christoph Hellwig
2016-04-18 15:21 ` Sinan Kaya
2016-04-18 15:40 ` Christoph Hellwig
2016-04-18 17:47 ` Sinan Kaya
2016-04-19 7:50 ` Sinan Kaya
2016-04-18 12:12 ` Christoph Hellwig
2016-04-18 13:06 ` okaya
2016-04-18 13:10 ` Christoph Hellwig
2016-04-18 13:49 ` Sinan Kaya
2016-04-18 13:59 ` Christoph Hellwig [this message]
2016-04-18 15:15 ` Timur Tabi
2016-04-18 15:22 ` Sinan Kaya
2016-04-19 18:22 ` Christoph Hellwig
2016-04-19 18:37 ` Sinan Kaya
2016-04-20 11:08 ` Eran Ben Elisha
2016-04-20 13:35 ` Sinan Kaya
2016-04-20 13:38 ` Sinan Kaya
2016-04-20 13:41 ` Timur Tabi
2016-04-20 18:40 ` Eran Ben Elisha
2016-04-20 18:42 ` Sinan Kaya
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