From: Ilias Apalodimas <ilias.apalodimas@linaro.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Yunsheng Lin <linyunsheng@huawei.com>,
Guillaume Tucker <guillaume.tucker@collabora.com>,
davem@davemloft.net, kuba@kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, linuxarm@openeuler.org,
hawk@kernel.org, akpm@linux-foundation.org, peterz@infradead.org,
will@kernel.org, jhubbard@nvidia.com, yuzhao@google.com,
mcroce@microsoft.com, fenghua.yu@intel.com, feng.tang@intel.com,
jgg@ziepe.ca, aarcange@redhat.com, guro@fb.com,
"kernelci@groups.io" <kernelci@groups.io>
Subject: Re: [PATCH net-next v6] page_pool: disable dma mapping support for 32-bit arch with 64-bit DMA
Date: Mon, 15 Nov 2021 20:48:30 +0200 [thread overview]
Message-ID: <YZKrfvt01uTosWc8@apalos.home> (raw)
In-Reply-To: <YZKgFqwJOIEObMg7@infradead.org>
Hi Christoph,
On Mon, Nov 15, 2021 at 09:59:50AM -0800, Christoph Hellwig wrote:
> This is just popping out of nowhere on lkml, but yes ARM LPAE
> uses a 64-bit dma_addr_t, as a 64-bit phys_addr_t implies that.
> Same for x86-32 PAE and similar cases on MIPS and probably a few
> other architectures.
>
> But what is the actual problem with a 32-bit virtual and 64-bit
> pysical/dma address? That is a pretty common setup and absolutely
> needs to be deal with in drivers and inrastructure.
page_pool (the API in question), apart from allocating memory can manage
the mappings for you. However while doing so it stores some parts (incl
the dma addr) in struct page. The code in there could be simplified if
we skipped support of the 'mapping' feature for 32-bit architectures with
64-bit DMA. We thought no driver was using the mapping feature (on 32bits)
and cleaned up that part, but apparently we missed
'32-bit -- LPAE -- page pool manages DMA mappings'
Regards
/Ilias
next prev parent reply other threads:[~2021-11-16 0:30 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-13 9:19 [PATCH net-next v6] page_pool: disable dma mapping support for 32-bit arch with 64-bit DMA Yunsheng Lin
2021-10-13 10:21 ` Jesper Dangaard Brouer
2021-10-15 10:00 ` patchwork-bot+netdevbpf
2021-11-09 9:58 ` Guillaume Tucker
2021-11-09 12:02 ` Yunsheng Lin
2021-11-12 9:21 ` Guillaume Tucker
2021-11-15 3:34 ` Yunsheng Lin
2021-11-15 11:53 ` Ilias Apalodimas
2021-11-15 12:10 ` Ilias Apalodimas
2021-11-15 12:21 ` Yunsheng Lin
2021-11-15 14:39 ` Jesper Dangaard Brouer
2021-11-15 18:55 ` Ilias Apalodimas
2021-11-17 11:52 ` Jesper Dangaard Brouer
2021-11-15 17:59 ` Christoph Hellwig
2021-11-15 18:48 ` Ilias Apalodimas [this message]
2021-11-15 18:53 ` Christoph Hellwig
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