From: Christoph Hellwig <hch@lst.de>
To: Robin Murphy <robin.murphy@arm.com>
Cc: axboe@fb.com, heikki.krogerus@linux.intel.com, sagi@grimberg.me,
saravanak@google.com, konrad.wilk@oracle.com, marcorr@google.com,
gregkh@linuxfoundation.org, rafael.j.wysocki@intel.com,
linux-kernel@vger.kernel.org, andriy.shevchenko@linux.intel.com,
kbusch@kernel.org, bgolaszewski@baylibre.com,
iommu@lists.linux-foundation.org, jroedel@suse.de,
linux-nvme@lists.infradead.org, erdemaktas@google.com,
dan.j.williams@intel.com, Jianxiong Gao <jxgao@google.com>,
hch@lst.de, m.szyprowski@samsung.com
Subject: Re: [PATCH 1/3] Adding page_offset_mask to device_dma_parameters
Date: Thu, 28 Jan 2021 19:15:57 +0100 [thread overview]
Message-ID: <20210128181557.GA11790@lst.de> (raw)
In-Reply-To: <2863b6d2-47f6-51fa-f60c-ba24904818e9@arm.com>
On Thu, Jan 28, 2021 at 05:27:25PM +0000, Robin Murphy wrote:
> On 2021-01-28 00:38, Jianxiong Gao wrote:
>> Some devices rely on the address offset in a page to function
>> correctly (NVMe driver as an example). These devices may use
>> a different page size than the Linux kernel. The address offset
>> has to be preserved upon mapping, and in order to do so, we
>> need to record the page_offset_mask first.
>>
>> Signed-off-by: Jianxiong Gao <jxgao@google.com>
>> ---
>> include/linux/device.h | 1 +
>> include/linux/dma-mapping.h | 17 +++++++++++++++++
>> 2 files changed, 18 insertions(+)
>>
>> diff --git a/include/linux/device.h b/include/linux/device.h
>> index 1779f90eeb4c..f44e0659fc66 100644
>> --- a/include/linux/device.h
>> +++ b/include/linux/device.h
>> @@ -292,6 +292,7 @@ struct device_dma_parameters {
>> */
>> unsigned int max_segment_size;
>> unsigned long segment_boundary_mask;
>> + unsigned int page_offset_mask;
>
> Could we call this something more like "min_align_mask" (sorry, I can't
> think of a name that's actually good and descriptive right now).
> Essentially I worry that having "page" in there is going to be too easy to
> misinterpret as having anything to do what "page" means almost everywhere
> else (even before you throw IOMMU pages into the mix).
>
> Also note that of all the possible ways to pack two ints and a long, this
> one is the worst ;)
The block layer uses virt_boundary for the related concept, but that
is pretty horrible too.
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next prev parent reply other threads:[~2021-01-28 18:16 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-28 0:38 [PATCH 0/3] Adding offset keeping option when mapping data via SWIOTLB.* Jianxiong Gao
2021-01-28 0:38 ` [PATCH 1/3] Adding page_offset_mask to device_dma_parameters Jianxiong Gao
2021-01-28 17:27 ` Robin Murphy
2021-01-28 18:15 ` Christoph Hellwig [this message]
2021-01-28 0:38 ` [PATCH 2/3] Add swiotlb offset preserving mapping when dma_dma_parameters->page_offset_mask is non zero Jianxiong Gao
2021-01-28 17:15 ` Konrad Rzeszutek Wilk
2021-01-28 17:34 ` Keith Busch
2021-01-28 18:16 ` Christoph Hellwig
2021-01-28 0:38 ` [PATCH 3/3] Adding device_dma_parameters->offset_preserve_mask to NVMe driver Jianxiong Gao
2021-01-28 18:00 ` Robin Murphy
2021-01-28 18:18 ` Christoph Hellwig
2021-01-28 8:04 ` [PATCH 0/3] Adding offset keeping option when mapping data via SWIOTLB.* Greg KH
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