From: Christoph Hellwig <hch@lst.de>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Robin Murphy <robin.murphy@arm.com>,
Nikita Yushchenko <nikita.yoush@cogentembedded.com>,
Will Deacon <will.deacon@arm.com>,
linux-arm-kernel@lists.infradead.org,
Catalin Marinas <catalin.marinas@arm.com>,
linux-kernel@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
Simon Horman <horms@verge.net.au>,
Bjorn Helgaas <bhelgaas@google.com>,
artemi.ivanov@cogentembedded.com, fkan@apm.com,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v2] arm64: do not set dma masks that device connection can't handle
Date: Tue, 10 Jan 2017 15:59:14 +0100 [thread overview]
Message-ID: <20170110145914.GE27156@lst.de> (raw)
In-Reply-To: <6116278.nQQUSuo3l4@wuerfel>
On Tue, Jan 10, 2017 at 02:42:23PM +0100, Arnd Bergmann wrote:
> It's a much rarer problem for the IOMMU case though, because it only
> impacts devices that are restricted to addressing of less than 32-bits.
>
> If you have an IOMMU enabled, the dma-mapping interface does not care
> if the device can do wider than 32 bit addressing, as it will never
> hand out IOVAs above 0xffffffff.
That's absolutely not the case. IOMMUs can and do generate addresses
larger than 32-bit. Also various platforms have modes where an IOMMU
can be used when <= 32-bit addresses are used and bypassed if full 64-bit
addressing is supported and I/O isolation is not explicitly requested.
next prev parent reply other threads:[~2017-01-10 14:59 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-09 7:30 [PATCH v2] arm64: do not set dma masks that device connection can't handle Nikita Yushchenko
2017-01-10 11:51 ` Will Deacon
2017-01-10 12:47 ` Nikita Yushchenko
2017-01-10 13:12 ` Arnd Bergmann
2017-01-10 13:25 ` Robin Murphy
2017-01-10 13:42 ` Arnd Bergmann
2017-01-10 14:16 ` Robin Murphy
2017-01-10 15:06 ` Arnd Bergmann
2017-01-11 12:37 ` Nikita Yushchenko
2017-01-11 16:21 ` Arnd Bergmann
2017-01-11 18:28 ` Robin Murphy
2017-01-10 14:59 ` Christoph Hellwig [this message]
2017-01-10 14:01 ` Nikita Yushchenko
2017-01-10 14:57 ` Christoph Hellwig
2017-01-10 14:51 ` Christoph Hellwig
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170110145914.GE27156@lst.de \
--to=hch@lst.de \
--cc=arnd@arndb.de \
--cc=artemi.ivanov@cogentembedded.com \
--cc=bhelgaas@google.com \
--cc=catalin.marinas@arm.com \
--cc=fkan@apm.com \
--cc=horms@verge.net.au \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-renesas-soc@vger.kernel.org \
--cc=nikita.yoush@cogentembedded.com \
--cc=robin.murphy@arm.com \
--cc=will.deacon@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox