From: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
To: Alex Feinman <alex@alexfeinman.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Contiguous DMA buffer view for a custom device (Intel/x86)
Date: Mon, 20 Aug 2018 21:58:04 +0100 [thread overview]
Message-ID: <20180820215804.67c78e3d@alans-desktop> (raw)
In-Reply-To: <CAGXJtFFjVTqYraM0OFipYnNbdLt_BojP5U8WhJETLgw4XWehGQ@mail.gmail.com>
> b) IOMMU can solve this problem for me by providing a device-specific
> contiguous view of a fragmented physical memory allocation
> c) In order to enable IOMMU do the above, I need to allocate DRHDs and
> DMARs in BIOS initialization (I build my own BIOS)
Yes. The EDK2 firmware toolkit has all the bits you need in it I think.
https://firmware.intel.com/sites/default/files/Intel_WhitePaper_Using_IOMMU_for_DMA_Protection_in_UEFI.pdf
isn't quite on the topic you want but it does explain it fairly well in
passing.
https://software.intel.com/en-us/blogs/2009/03/02/intels-virtualization-for-directed-io-aka-iommu-part-1
is a bit out of date but may help too.
> Please, let me know if I am on the right track? Of course I realize that
> implementing SGDMA would be the best option, but short of that and blocking
> out some physical memory on boot, what are my options?
If performance is absolutely critical simply stealing a chunk of memory
in the firmware and describing it your device some other way is ugly, but
for a custom solution I guess anything goes 8)
Alan
next prev parent reply other threads:[~2018-08-20 20:58 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-20 20:39 Contiguous DMA buffer view for a custom device (Intel/x86) Alex Feinman
2018-08-20 20:58 ` Alan Cox [this message]
2018-08-21 23:50 ` Alex Feinman
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